Cylindrical Mass Research Articles

A Self‐Powered Dynamic Displacement Monitoring System Based on Triboelectric Accelerometer

AbstractAn integrated self‐powered dynamic displacement monitoring system by utilizing a novel triboelectric accelerometer for structural health monitoring is proposed and implemented in this study, which can show the dynamic displacement and transmit the alarming signal by accurately sensing the vibration acceleration. The fabricated triboelectric accelerometer based on the noncontact freestanding triboelectric nanogenerator consists of an outer transparent sleeve tube and an inner cylindrical inertial mass that is suspended by a highly stretchable silicone fiber. One pair of copper film electrodes is deposited by physical vapor deposition on nylon film and adhered on the inner wall of the outer tube, while a fluorinated ethylene propylene film with nanowire structures is adhered on the surface of the inner cylindrical inertial mass. The experimental results show that proposed triboelectric accelerometer can accurately sense the vibration acceleration with a high sensitivity of 0.391 V s2 m−1. In particular, the developed accelerometer has superior performance within the low‐frequency range. One of the most striking features is that the commercial accelerometer using piezoelectric material is strongly dominated by high‐order harmonics, which can cause confusion in computer data analysis. In contrast, the triboelectric accelerometer is only dominated by the base resonance mode.

Nonstationary plane contact problem in theory of elasticity for conformal cylindrical surfaces

A numerical–analytical approach is described to investigate the process of impact interaction between a long smooth rigid body and the surface of a circular cylindrical cavity in elastic space. A non-stationary mixed initial boundary value problem is formulated with a priori unknown boundaries moving with variable velocity. The problem is solved using the methods of the theory of integral transforms, expansion of desired variables into a Fourier series, and the quadrature method to reduce the problem to solving a system of linear algebraic equations at each time step. Some concrete numerical computations are presented. The cylindrical body mass and radius impact on the profile of the transient process of contact interaction has been analysed.

Theoretical Analysis of an Optical Accelerometer Based on Resonant Optical Tunneling Effect.

Acceleration is a significant parameter for monitoring the status of a given objects. This paper presents a novel linear acceleration sensor that functions via a unique physical mechanism, the resonant optical tunneling effect (ROTE). The accelerometer consists of a fixed frame, two elastic cantilevers, and a major cylindrical mass comprised of a resonant cavity that is separated by two air tunneling gaps in the middle. The performance of the proposed sensor was analyzed with a simplified mathematical model, and simulated using finite element modeling. The simulation results showed that the optical Q factor and the sensitivity of the accelerometer reach up to 8.857 × 107 and 9 pm/g, respectively. The linear measurement range of the device is ±130 g. The work bandwidth obtained is located in 10–1500 Hz. The results of this study provide useful guidelines to improve measurement range and resolution of integrated optical acceleration sensors.

Engineered metabarrier as shield from seismic surface waves

Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by burying sub-wavelength resonant structures under the soil surface. Each resonant structure consists of a cylindrical mass suspended by elastomeric springs within a concrete case and can be tuned to the resonance frequency of interest. The design allows controlling seismic waves with wavelengths from 10-to-100 m with meter-sized resonant structures. We develop an analytical model based on effective medium theory able to capture the mode conversion mechanism. The model is used to guide the design of metabarriers for varying soil conditions and validated using finite-element simulations. We investigate the shielding performance of a metabarrier in a scaled experimental model and demonstrate that surface ground motion can be reduced up to 50% in frequency regions below 10 Hz, relevant for the protection of buildings and civil infrastructures.

High pressure mass spectrometry of volatile organic compounds with ambient air buffer gas.

There are many chemical measurement scenarios that would benefit from hand portable mass spectrometry tools including forensics, environmental monitoring, and safety and security. High pressure mass spectrometry (HPMS) facilitates miniaturization by significantly reducing vacuum system requirements. Previous work demonstrated HPMS using helium buffer gas, but HPMS conducted using ambient air would further reduce the size and weight of a portable instrument while also reducing logistical demands by eliminating the need for a helium supply. Mass spectrometry was performed at pressures exceeding 1Torr with ambient air as the buffer gas. A glow discharge electron ionization source and a miniature cylindrical ion trap mass analyzer with a radius of 0.5mm were used. Mass analysis was possible at these pressures with increased radiofrequency (RF) drive frequencies (10MHz) compared with commercial ion traps (~1MHz). A differentially pumped chamber was used so that mass spectrometry could be performed at high pressures and detection performed at low pressures with an electron multiplier. HPMS with air buffer gas was demonstrated using a suite of volatile organic compounds (VOCs). The glow discharge ionization source was optimized for operation using air. Mass spectral peak widths increased a factor of 8 compared with helium, as expected, but useful chemical information was still acquired. A mixture of VOCs was detected with ambient air as the buffer gas, showing that valuable mass information can be gained using HPMS without the requirement of an onboard buffer gas source. HPMS significantly reduces the pumping requirements required for miniature mass spectrometers and the use of ambient air buffer gas further reduces size, weight, and logistics requirements. Mass analysis at high pressures of ambient air is another important step for the development of hand portable mass spectrometers. Copyright © 2016 John Wiley & Sons, Ltd.

Solitary Myxoid Neurofibroma of the Palm.

Dear sir A 21-year-old femalepresented with a four-month history of a gradually-enlarging mass of her non-dominant left palm. She denied pain at rest, but noted some discomfort when firm pressure was applied to the area. She also noted mild tingling in the middle and ring fingers. The patient had no history of trauma or prior surgery to the area. Past medical history was unremarkable. On physical exam there was a nodular mass palpable at the base of the middle and ring fingers at the level of the distal palmar crease, measuring approximately one x one centimeters (cm). Sensation to light touch and capillary refill were normal throughout. She had full wrist and digital range of motion. An MRI of the left hand demonstrated a homogenous cylindrical mass measuring 1.9 × 0.7 × 0.8 cm, that was hypo- and hyperintense on T1- and T2-weighted imaging, respectively. The patient underwent surgical excision under tourniquet control, with intravenous sedation and local anesthetic. The mass was seen tenting the common sensory nerve to the ring and middle fingers. The nerve was mobilized and neurolysed from the underlying mass, which was subsequently excised from the surrounding soft tissues. After hemostasis of feeder vessels was achieved, the skin was closed. Gross examination of the specimen revealed a pale yellow well-demarcated, elongated mass measuring 2.0 × 0.7 × 0.7 cm. (Fig. 1).

Gemistocytic astrocytoma in the spinal cord in a dog: a case report

ABSTRACT This paper reports a case of a rare variant of the cervical spinal cord astrocytoma diagnosed in a dog with progressive neurological signs, initially asymmetrical, not ambulatory tetraparesis, segmental reflexes and normal muscle tone in all four limbs and absence of pain upon palpation of the cervical spine. Myelography revealed attenuation of the ventral and dorsal contrast line in the third region of the fifth cervical vertebra. At necropsy intramedullary cylindrical mass that stretched from the third to the sixth cervical vertebra, which replaced all the gray matter of the spinal cord was observed. In the histological study, there was the replacement of the substance by neoplastic cells mantle arranged loosely. The cells were large and slightly rounded. The eosinophilic cytoplasm was well defined, sometimes forming processes interconnecting cells. The nucleus was eccentric, round, oval or kidney-shaped, and the nucleolus was evident. Thus, the microscopic changes observed in the cervical spinal cord were consistent with gemistocytic astrocytoma.

Additive Manufacturing Design and Fabrication of Ceramic Cylindrical Ion Trap Mass Analyzer Chips for Miniaturized Mass Spectrometer Smart-Device (Internet of Things) Applications

The current computing power and network capabilities of handheld smart devices is helping to drive the development of new sensors, enabling the Internet of things. A chip-based mass spectrometer technology promises to offer a smart-device autonomous microsystem chemical analysis capability for sample determination and process monitoring for multiple applications in a small low-power instrument package. This project focuses on the development of cylindrical ion trap (CIT) mass analyzer chips fabricated using three-dimensional (3-D) additive manufacturing (AM) and planar low temperature cofired ceramic thick film processes for a chip-based mass spectrometer microsystem. The CIT is a mass analyzer composed of planar electrodes and operates by trapping and ejecting sample ions based on their mass in a radiofrequency field. Because of its simplicity, CITs may be easily miniaturized and connected in tandem to achieve multiplexing. AM materials and methods enable enhanced trap miniaturization through micromachining and electrode patterning methods, fast and cost-effective prototyping, batch fabrication, and material formulation flexibility. The current design incorporates three parallel ceramic plate metalized electrodes making up a singular trap geometry in a 10-mm2 ceramic chip, forming a mass analyzer of reduced size, mass, and power, with enhanced material robustness for extended range use and in harsh environments. Unique processes have been developed to produce these devices which include conformal metallization layers, adhesion layers, ceramic paste formulations, sacrificial supporting materials, and cofiring methods. Additionally, 3-D printing brings a unique design and fabrication capability enabling novel structures, material blending, and heterogeneous integration. With true digital control, the designs are easily scalable and shape agnostic.

General Polytropic Self-gravitating Cylinder Free-fall and Accreting Mass String with a Chain of Collapsed Objects

We present a theoretical model framework for general polytropic (GP) hydrodynamic cylinder under self-gravity of infinite length with axial uniformity and axisymmetry. For self-similar dynamic solutions, we derive valuable integrals, analytic asymptotic solutions, sonic critical curves, shock conditions, and global numerical solutions with or without expansion shocks. Among others, we investigate various dynamic solutions featured with central free-fall asymptotic behaviours, corresponding to a collapsed mass string with a sustained dynamic accretion from a surrounding mass reservoir. Depending on the allowed ranges of a scaling index a < -1, such cylindrical dynamic mass accretion rate could be steady, increasing with time and decreasing with time. Physically, such a collapsed mass string or filament would break up into a sequence of sub-clumps and segments as induced by gravitational Jeans instabilities. Depending on the scales involved, such sub-clumps would evolve into collapsed objects or gravitationally bound systems. In diverse astrophysical and cosmological contexts, such a scenario can be adapted on various temporal, spatial and mass scales to form a chain of collapsed clumps and/or compact objects. Examples include the formation of chains of proto-stars, brown dwarfs and gaseous planets along molecular filaments; the formation of luminous massive stars along magnetized spiral arms and circum-nuclear starburst rings in barred spiral galaxies; the formation of chains of compact stellar objects such as white dwarfs, neutron stars, and black holes along a highly condensed mass string. On cosmological scales, one can perceive the formation of chains of galaxies, chains of galaxy clusters or even chains of supermassive and hypermassive black holes in the Universe including the early Universe. All these chains referred to above include possible binaries.

Response of aluminum corrugated sandwich panels under foam projectile impact – Experiment and numerical simulation

The paper studied the dynamic response of square aluminum corrugated sandwich panels under projectile impact. The aluminum foam projectile was utilized to apply the impulse on the sandwich panels. In order to increase the applied impulse under controlled impact velocity ( V &lt; 200 m/s), a cylindrical Nylon mass was adhered to the back of foam projectile. Corrugated sandwich panels with two different configurations were tested and their typical deformation modes were obtained in the experiment. Based on the experiment, corresponding numerical simulations were presented. The energy absorption and deformation mechanism of corrugated sandwich panels were studied through the simulation. The influence of impact velocity, thickness of face sheet and wall thickness of corrugated core were discussed. The results indicated that the corrugated sandwich panels with smaller core height produce larger deformation than the panels with larger core height. The face sheets of corrugated sandwich panel absorbed comparable amount of energy with the corrugated core. The velocity histories show that under the combined action of aluminum foam projectile and nylon back mass, a second peak velocity of front face sheet can be produced during the impact process, which is defined as “accelerating impact stage” in current study. The influence of “accelerating impact stage” to the response of structures is sensitive to the impact velocity.

Augmented PMMA distribution: improvement of mechanical property and reduction of leakage rate of a fenestrated pedicle screw with diameter-tapered perforations.

OBJECTIVE This study investigated the optimum injection volume of polymethylmethacrylate (PMMA) to augment a novel fenestrated pedicle screw (FPS) with diameter-tapered perforations in the osteoporotic vertebral body, and how the distribution characteristics of PMMA affect the biomechanical performance of this screw. METHODS Two types of FPSs were designed (FPS-A, composed of 6 perforations with an equal diameter of 1.2 mm; and FPS-B, composed of 6 perforations each with a tapered diameter of 1.5 mm, 1.2 mm, and 0.9 mm from tip to head. Each of 28 human cadaveric osteoporotic vertebrae were randomly assigned to 1 of 7 groups: FPS-A1.0: FPS-A+1.0 ml PMMA; FPS-A1.5: FPS-A+1.5 ml PMMA; FPS-A2.0: FPS-A+2.0 ml PMMA; FPS-B1.0: FPS-B+1.0 ml PMMA; FPS-B1.5: FPS-B+1.5 ml PMMA; FPS-B2.0: FPS-B+2.0 ml PMMA; and conventional pedicle screws (CPSs) without PMMA. After the augmentation, 3D CT was performed to assess the cement distribution characteristics and the cement leakage rate. Axial pullout tests were performed to compare the maximum pullout force thereafter. RESULTS The CT construction images showed that PMMA bone cement formed a conical mass around FPS-A and a cylindrical mass around FPS-B. When the injection volume was increased from 1.0 ml to 2.0 ml, the distribution region of the PMMA cement was enlarged, the PMMA was distributed more posteriorly, and the risk of leakage was increased. When the injection volume reached 2.0 ml, the risk of cement leakage was lower for screws having diameter-tapered perforations. The pullout strengths of the augmented FPS-A groups and FPS-B groups were higher than that of the CPS group (p < 0.0001). All FPS-B groups had a higher pullout strength than the FPS-A groups. CONCLUSIONS The diameter of the perforations affects the distribution of PMMA cement. The diameter-tapered design enabled PMMA to form larger bone-PMMA interfaces and achieve a relatively higher pullout strength, although statistical significance was not reached. Study results indicated 1.5-ml of PMMA was a conservative volume for PMMA augmentation; more cement injection would significantly increase the risk of cement leakage.

The design and performance of a prototype water Cherenkov optical time-projection chamber

A first experimental test of tracking relativistic charged particles by ‘drifting’ Cherenkov photons in a water-based optical time-projection chamber (OTPC) has been performed at the Fermilab Test Beam Facility. The prototype OTPC detector consists of a 77cm long, 28cm diameter, 40kg cylindrical water mass instrumented with a combination of commercial 5.1×5.1cm2 micro-channel plate photo-multipliers (MCP-PMT) and 6.7×6.7cm2 mirrors. Five MCP-PMTs are installed in two columns along the OTPC cylinder in a small-angle stereo configuration. A mirror is mounted opposite each MCP-PMT on the inner surface of the detector cylinder, effectively increasing the photo-detection efficiency and providing a time-resolved image of the Cherenkov light on the opposing wall. Each MCP-PMT is coupled to an anode readout consisting of thirty 50Ω microstrips. A 180-channel data acquisition system digitizes the MCP-PMT signals on one end of the microstrips using the PSEC4 waveform sampling-and-digitizing chip operating at a sampling rate of 10.24Gigasamples-per-second. The single-ended microstrip readout determines the time and position of a photon arrival at the face of the MCP-PMT by recording both the direct signal and the pulse reflected from the unterminated far end of the strip. The detector was installed on the Fermilab MCenter secondary beam-line behind a steel absorber where the primary flux is multi-GeV muons. Approximately 80 Cherenkov photons are detected for a through-going muon track in a total event duration of ~2ns. By measuring the time-of-arrival and the position of individual photons at the surface of the detector to ≤100ps and a few mm, respectively, we have measured a spatial resolution of ~15mm for each MCP-PMT track segment, and, from linear fits over the entire track length of ~40cm, an angular resolution on the track direction of ~60mrad.

Material model for modeling clay at high strain rates

Modeling clay is a soft malleable material made from oils and waxes. This material is fundamental for ballistic evaluation of body armors because it is used as backing material in ballistic tests. After a ballistic impact, a back-face indentation is measured to assess performance of the armor. Due to the important role of modeling clay in this particular application, its mechanical characterization and comprehension of penetration mechanics are essential for development of new personal protection systems. This paper presents a two-step computational methodology to calibrate parameters of a Cowper–Symonds material model for modeling clay at characteristic strain rates up to 1.8×104 s−1. In the first stage, a high-speed camera is used to record the penetration of a gas-gun launched cylindrical mass with a hemispherical cap into a block of clay. Image-processing software is used to capture the tail of the projectile as it penetrates into the clay. These data are then used to sample the penetration depth as function of time. In the second stage, an in-house developed model of penetration, based on both the spherical cavity expansion theory and the Tate penetration equation, is used to determine, by inverse analysis, the parameters of the Cowper–Symonds clay model. The proposed constitutive relationship for clay and the determined material parameters can be applied accurately to problems involving high strain rates.

Additive Manufacturing Design and Fabrication of Ceramic Cylindrical Ion Trap Mass Analyzer Chips for Miniaturized Mass Spectrometer Smart-Devices

A chip based mass spectrometer technology promises to offer smart-device autonomous microsystem chemical analysis capability for sample determination and process monitoring for multiple applications in a small low power instrument package. This project focuses on the development of cylindrical ion trap mass analyzer chips fabricated using 3D Additive Manufacturing and planar Low Temperature Co-Fired Ceramic thick film processes toward the realization of a chip based mass spectrometer microsystem. The cylindrical ion trap (CIT) is a mass analyzer comprised of planar electrodes and operates by trapping and ejecting sample ions based on their mass in an RF field. Because of its simplicity CITs may be easily miniaturized and connected in tandem to achieve multiplexing. Additive manufacturing materials and methods enable enhanced trap miniaturization through micro machining and electrode patterning methods, fast and cost effective prototyping, batch fabrication, and material formulation flexibility. The current design incorporates three parallel ceramic plate metalized electrodes making up a singular trap geometry in a 10mm2 ceramic chip, forming a mass analyzer of reduced size, mass, and power, with enhanced material robustness for extended range use and in harsh environments. Unique processes have been developed to produce these devices which include conformal metallization layers, adhesion layers, ceramic paste formulations, sacrificial supporting materials, and co-firing methods. Additionally, 3D printing brings a unique design and fabrication capability enabling novel structures, material blending and heterogeneous integration. With true digital control, the designs are easily scalable and shape agnostic.

Fine Structure and Molecular Phylogeny of Parametopidium circumlabens (Ciliophora: Armophorea), Endocommensal of Sea Urchins.

Metopid armophoreans are ciliates commonly found in anaerobic environments worldwide; however, very little is known of their fine structure. In this study, the metopid Parametopidium circumlabens (Biggar and Wenrich 1932) Aescht, 1980, a common endocommensal of sea urchins, is investigated for the first time with emphasis on transmission electron microscopy, revealing several previously unknown elements of its morphology. Somatic dikinetids of P. circumlabens have a typical ribbon of transverse microtubules, an isolated microtubule near triplets 4 and 5 of the anterior kinetosome, plus two other microtubules between anterior and posterior kinetosomes, a short kinetodesmal striated fiber and long postciliary microtubules. In the dikinetids of the perizonal stripe, the kinetodesmal fiber is very pronounced, and there is a conspicuous microfibrillar network system associated with the kinetosomes. A new structure, shaped as a dense, roughly cylindrical mass surrounded by microtubules, is found associated with the posterior kinetosome of perizonal dikinetids. The paroral membrane is diplostichomonad and the adoral membranelles are of the "paramembranelle" type. Bayesian inference and maximum-likelihood analysis of the 18S-rDNA gene unambiguously placed P. circumlabens as sister group of the cluster formed by ((Atopospira galeata, Atopospira violacea) Metopus laminarius) + Clevelandellida, corroborating its classification within the Metopida.

“Volume-point” mass transfer constructal optimization based on flow resistance minimization with cylindrical element

Analogizing with Alebrahim and Bejan’s (Alebrahim and Bejan, 1999) heat conduction model of a cylindrical assembly, a mass transfer model with cylindrical porous media is investigated in this paper. Constructal optimizations of the cylindrical element and first order assembly are carried out by taking minimum dimensionless maximum pressure drop (i.e., minimum dimensionless flow resistance with the specified total mass flow rate) as optimization objective and using analytical solution method. The results show that there exist optimal ratios of the internal and external parameters which lead to twice minimum dimensionless maximum pressure drops of the cylinders. Different from Alebrahim and Bejan’s cylindrical heat conduction model, there are three kinds of permeability materials in the cylindrical mass transfer model, and different parameters have different effects on the optimal constructs of the models. The constructal optimization of the model based on the minimization of dimensionless maximum pressure drop chases for the reduction of the limit pressure in the assembly, and its mass transfer performance can be improved simultaneously.

A purely flexible lightweight membrane-type acoustic metamaterial

This paper proposes a purely flexible lightweight membrane-type acoustic structure, wherein one kind of flexible lightweight rubber material takes the roles of mass and stiffness and another type of lightweight flexible EVA (ethylene–vinyl acetate copolymer) or plastic material functions as the localized stiffness for each unit. Because both the scatterers and base are constituted by the same material, this type of structure breaks the limitation that the metamaterials and phononic crystals need different materials with relatively large density and elasticity modulus ratios to play the roles of the scatterers and base respectively. Based on the band structures with different units, mass block shapes and size parameters, it is suggested that the shapes of the mass block can significantly affect the band structure. In addition, this type of structure could not only open a full band gap in the low-frequency range below 500 Hz, but also obtain an ultra-low-frequency bending wave band gap in the range below 100 Hz. Finally, we take into account the semi-infinite medium as a component, and calculate the sound transmission loss (STL) to evaluate the interaction between the structure and air. An experimental validation employing the cylindrical mass structure was developed to directly support the simulation results. Since the structures proposed in this study have achieved a purely flexible lightweight design, there exists an important promotion effect to realize the engineering applications of the acoustic metamaterials in practice.

A field-portable membrane introduction mass spectrometer for real-time quantitation and spatial mapping of atmospheric and aqueous contaminants.

Environmental concentrations of volatile and semivolatile organic compounds (VOC/SVOCs) can vary dramatically in time and space under the influence of environmental conditions. In an industrial setting, multiple point and diffuse sources can contribute to fugitive emissions. Assessments and monitoring programs using periodic grab sampling provide limited information, often with delay times of days or weeks. We report the development and use of a novel, portable membrane introduction mass spectrometry (MIMS) system capable of resolving and quantifying VOC and SVOCs with high spatial and temporal resolution, in the field, in real-time. An electron impact ionization cylindrical ion trap mass spectrometer modified with a capillary hollow fiber polydimethylsiloxane membrane interface was used for continuous air and water sampling. Tandem mass spectrometry and selected ion monitoring scans performed in series allowed for the quantitation of target analytes, and full scan mode was used to survey for unexpected analytes. Predeployment and in-field external calibrations were combined with a continuously infused internal standard to enable real-time quantitation and monitor instrument performance. The system was operated in a moving vehicle with internet-linked data processing and storage. Software development to integrate MIMS and relevant meta-data for visualization and geospatial presentation in Google Earth is presented. Continuous quantitation enables the capture of transient events that may be missed or under-represented by traditional grab sampling strategies. Real-time geospatial maps of chemical concentration enable adaptive sampling and in-field decision support. Sample datasets presented in this work were collected in Northern Alberta in 2010-2012.

Determination of the Equivalence Principle Violation Signal for the MICROSCOPE Space Mission: Optimization of the Signal Processing

The MICROSCOPE space mission aims at testing the Equivalence Principle (EP) with an accuracy of $10^{-15}$. The test is based on the precise measurement delivered by a differential electrostatic accelerometer on-board a drag-free microsatellite which includes two cylindrical test masses submitted to the same gravitational field and made of different materials. The experiment consists in testing the equality of the electrostatic acceleration applied to the masses to maintain them relatively motionless at a well-known frequency. This high precision experiment is compatible with only very little perturbations. However, aliasing arises from the finite time span of the measurement, and is amplified by measurement losses. These effects perturb the measurement analysis. Numerical simulations have been run to estimate the contribution of a perturbation at any frequency on the EP violation frequency and to test its compatibility with the mission specifications. Moreover, different data analysis procedures have been considered to select the one minimizing these effects taking into account the uncertainty about the frequencies of the implicated signals.

Cottontail Rabbit Papillomavirus Infection in a Desert Cottontail (Sylvilagus audubonii) from Colorado, USA

A wild-caught desert cottontail rabbit (Sylvilagus audubonii) from Colorado was observed to have large, pedunculated, dark cutaneous lesions on its abdomen and cylindrical masses on its mouth. Morphologically, the masses were consistent with previous reports of virally induced papillomas. Subsequent DNA analysis indicated widespread infection with cottontail rabbit papillomavirus.