Episodes Of Destruction Research Articles

Relapsing polychondritis.

Relapsing polychondritis (RP) is a rare multisystem autoimmune disease of unknown origin characterized by recurrent episodes of inflammation and progressive destruction of cartilaginous tissues. Elastic cartilage of the ears and nose, hyaline cartilage of peripheral joints, vertebral fibrocartilage and tracheobronchial cartilage, as well as proteoglycan-rich structures of the eye, heart, blood vessels or inner ear may all be affected. In most patients RP manifests in a fluctuating but progressive course which eventually results in a significant shortening of life expectancy. The relatively uncommon occurrence, the unknown etiopathogenesis, the ambiguous clinical pattern, as well as the variety in its course and response to therapy may all contribute to the difficulties the physician must overcome when managing RP. Beside describing the main features of RP and seven clinical cases of our own, in the present review we focus on recent findings in the etiopathogenesis and novel treatment options.

Reduced violent behavior following biochemical therapy

Reduced violent behavior following biochemical therapy. We conducted an outcome study to measure the effectiveness of biochemical therapy for 207 consecutive patients presenting with a diagnosed behavior disorder. The treatment protocols were based on clinical evaluation and our past experience in the treatment of 8000 patients with behavior disorders at the Pfeiffer Treatment Center (PTC) over a 10-year period. Each test subject was screened for chemical imbalances previously found in high incidence in this population, including metal-metabolism disorders, methylation abnormalities, disordered pyrrole chemistry, heavy-metal overload, glucose dyscontrol, and malabsorption. The clinical procedure included a medical history, assay of 90 biochemical factors, and a physical examination. Standardized treatment protocols were applied for each imbalance that was identified. The frequencies of physical assaults and destructive episodes were determined using a standardized behavior scale before and after treatment, with follow-up ranging from 4 to 8 months. ResultsSeventy-six percent of the test subjects achieved compliance during the treatment period. The remaining 24% were reported to have discontinued the therapy. A reduced frequency of assaults was reported by 92% of the compliant assaultive patients, with 58% achieving elimination of the behavior. A total of 88% of compliant destructive patients exhibited a reduced frequency of destructive incidents and 53% achieved elimination of the behavior. Statistical significance was found for reduced frequency of assaults (t=7.74, p<0.001) and destructive incidents (t= 8.77, p<0.001). The results of this outcome study strongly suggest that individualized biochemical therapy may be efficacious in achieving behavioral improvements in this patient population.

Reflections of Georgian-Iranian Cultural Interrelations in Seventeenth-Century Georgian Fine Art

The study of new aspects of sixteenthand seventeenth-century Georgian-Iranian cultural interrelations is closely linked with the history of both countries. During the reign of the Safavid dynasty, the interest of Persia grew towards the rich, beautiful and strategically important country of Georgia, where Persia's policy of conquest reached its highest point in the seventeenth century, the period of the rule of Shah Abbas the Great (1587-1629). From this century onwards, Georgia, mostly its eastern part, under the political influence of Persia, became much more closely linked with Iranian culture, which influenced not only Georgian secular literature, architecture and book illumination,' but the Georgian way of life as well.2 On the other hand, nearly the same process is traceable in Persia: Georgian themes were introduced into Persian culture apparently at the same time, a clear example of which can be seen in the poetry of the Shirazian poet Abdi Beg Shirazi (1515-1585), where, inter alia, one may find reference to Georgian personages as well. The poet refers to a painting, no longer surviving today, from the Ja'far Abad palace of Shah Tahmasp in Qazvin, one scene of which evidently represented a battle against Georgians, which has been identified with the episode of the destruction of the Vardzia fortress and church at the time of Shah Tahmasp's third invasion of Georgia (1552).3 The Russian scholar Yuri Marr remarks that Georgians were depicted on the frescoes from the palaces of Hasht Behesht and Chehel Sotun in Isfahan as well. Particularly worthy of comment is the fragment from an 'Ali Qapu palace painting, portraying a man whose open book in-

Aeromagnetic survey over an active stratovolcano in central Mexico

In this paper, we briefly summarize an aeromagnetic survey over a large stratovolcano (Popocatepetl) and surrounding volcanic terrain in central Mexico to show the potential that recent improvements in these methods have in studying active volcanoes. After a decades-long period of quiescence, the Popocatepetl volcano reawakened in 1994. Background seismicity showed a two-fold increase in October 1994. This was followed on 21 December by a swarm of volcano-tectonic events and tremors accompanying a large ash plume. Popocatepetl is an andesitic stratovolcano (Figure 1) in the central sector of the Plio-Quaternary Trans-Mexican volcanic belt (TMVB)—a continental arc associated with subduction of the Cocos and Rivera plates along the Middle Ainerican trench, and oriented almost E-W from the Pacific Ocean to the Gulf of Mexico. The TMVB volcanic-capped plateau is heavily populated. Mexico City is just 70 km away. Figure 1. Landsat thematic mapper image of the Iztaccihuatl-Popocatepetl volcanic range, eastern Mexico. The volcanic range is formed by several stratovolcanoes aligned north-south. Popocatepetl forms the southern end of a north-south trending range of large volcanic structures. The Popocatepetl stratovolcano has evolved through alternate periods of cone formation and destruction, with major cataclysmic events that destroyed ancient cones followed by formation of dome complexes and new summit cones. Recent activity at first was characterized by emission of ash rich in nonjuvenile material and volatiles, marked by intense seismicity with volcano-tectonic earthquakes (VT), long-period (LP) and tremor events. The ash and gas clouds from some events distributed ash over Mexico City and surrounding areas, with lapilli and small blocks falling over the volcano flanks. In March 1996, a dacitic dome built within the summit crater; magnetic activity to the present has been characterized by episodes of dome growth and destruction. Activity during December 2000 was particularly intense and, on 21 January 2001, a major explosive event …

Geology of El Misti volcano near the city of Arequipa, Peru

Approximately 750 000 people live at risk in the city of Arequipa, whose center lies 17 km from the summit (5820 masl [meters above sea level]) of the active El Misti volcano. The composite edifice comprises a stratovolcano designated Misti 1 (ca. 833– 112 ka), partially overlapped by two stratocones designated Misti 2 and Misti 3 (112 ka and younger), and a summit cone Misti 4 (11 ka and younger). Eight groups of lava flows and pyroclastic deposits indicate the following volcanic history. (1) Three cones have been built up since ca. 112 ka at an average eruptive rate of 0.63 km3/k.y. (2) Several episodes of growth and destruction of andesitic and dacitic domes triggered dome-collapse avalanches and block-and-ash-flows. Deposition of these flows alternated with explosive events, which produced pyroclastic-flow deposits and tephra-fall and surge deposits. (3) Nonwelded, dacitic ignimbrites may reflect the formation of a 6 × 5 km incremental caldera collapse on Misti 2 (ca. 50 000 and 40 000 yr B.P.) and a 2 × 1.5 km summit caldera on Misti 3 (ca. 13 700 to 11 300 yr B.P.). (4) Tens of pyroclastic flows and at least 20 tephra falls were produced by Vulcanian and sub-Plinian eruptions since ca. 50 ka. On average, ash falls have occurred every 500 to 1500 yr, and pumice falls, every 2000 to 4000 yr. (5) Misti erupted relatively homogeneous andesites and dacites with a few rhyolites, but Misti 4 reveals a distinct mineral suite. Less evolved andesites prevail in scoriaceous products of group 4–1 including historical ash falls. Scoriae of Misti 4 and the ca. 2300–2050 yr B.P. banded pumice commonly show heterogeneous textures of andesite and rhyolite composition. This heterogeneity may reflect changes in physical conditions and magma mixing in the reservoir. (6) Deposits emplaced during the Vulcanian A.D. 1440– 1470 event and the sub-Plinian eruption(s) at ca. 2050 yr B.P. are portrayed on one map. The extent and volume of these deposits indicate that future eruptions of El Misti, even if moderate in magnitude, will entail considerable hazards to the densely populated area of Arequipa.

Controls on floc size in a continental shelf bottom boundary layer

Simultaneous in situ observations of floc size, waves, and currents in a continental shelf bottom boundary layer do not support generally accepted functional relationships between turbulence and floc size in the sea. In September and October 1996 and January 1997, two tripods were deployed in 70 m of water on the continental shelf south of Woods Hole, Massachusetts. On one a camera photographed particles in suspension 1.2 m above the bottom that had equivalent circular diameters larger than 250 μm, and on the other, three horizontally displaced acoustic current meters measured flow velocity 0.35 m above the bottom. The tripods were separated by ∼150 m. Typically, maximal floc diameter stayed relatively constant, around 1 mm, and it showed a dependence on turbulence parameters that was significantly weaker than that predicted by any model that assumes that turbulence‐induced stresses limit floc size. Occasionally, when waves and currents generated intense near‐bed turbulence, flocs were destroyed. These precipitous decreases in maximal floc size also were not predicted by conventional models. The correlation in time between episodes of floe destruction and elevated combined wave‐current stresses provides the first quantitative support for the hypothesis that floc size throughout bottom boundary layers can be controlled by breakup in the intensely sheared near‐bed region. These observations demand a reassessment of the forces limiting floc size in the sea, and they indicate the potential for significant simplifying assumptions in models of floc dynamics.

Remapping Koreatown: Folklore, Narrative and the Los Angeles Riots

charged with the beating of Rodney King, Los Angeles exploded into one of the most destructive episodes of civil unrest in American history.' Originally centered at the intersection of Florence Avenue and Normandie Avenue in the South Central district, acts of violence, looting and arson quickly spread to other parts of the city (Jencks 1993, 79-80).2 Koreatown, situated just to the north of South Central, found itself directly in the path of this maelstrom of destruction.3 As a result of the widespread arson that accompanied the looting of stores, large parts of the man-made environment were essentially erased from the landscape. In the aftermath of the riots, a landscape that had been defined by the spatial practices of the people who worked and lived in these areas had been deeply scarred and, in some instances, reduced to rubble. The text of the city, particularly in these two neighborhoods, had been forcibly rewritten by the destruction, and the earlier man-made landscape could only be interpolated through a palimpsestic rereading of the city.4 Although committees to both study the cause and effects of the riots and to rebuild Los Angeles were almost immediately established,5 in the considerable period between the physical destruction of places-and the implicit challenge to identities associated with those places embodied in that destructionand the envisioned phoenix-like rise of a rebuilt Los Angeles from the

Understanding diagnostic testing for periodontal diseases.

Probability computations are used to characterize new periodontal diagnostic tests and are an integral facet of risk assessment for periodontal diseases. However, misinterpretation of these data can result in confusion and erroneous conclusions regarding the relationship of test results to the presence or absence of disease in a subject, or to episodes of periodontal destruction at specific sites. This paper was written to provide clinicians with a primer to help in understanding calculations used to evaluate diagnostic tests and risk assessment.

Constructive and destructive episodes in the building of a young Oceanic Island, La Palma, Canary Islands, and genesis of the Caldera de Taburiente

The results of new field observations, 23 new KAr determinations and sixteen previously published determinations provide the basis for the reconstruction of the subaerial volcanic history of the island of La Palma, after the seamount activity represented by the materials of the Basal Complex. An eruptive phase between 2.0 and 1.3 Ma formed a large shield. A period of volcanic quiescence followed, until around 1 Ma, during which a large lateral collapse partly destroyed the former edifice. Between 1.05 and 0.7 Ma, activity was renewed in the shield and a N-S ridge was built in the southern part of the island. Around 0.7 Ma, two new large lateral collapses affected the western part of both edifices, and they were followed by eruptions between 0.71 and 0.65 Ma which built a new edifice that partly filled the depressions thus created. The Caldera de Taburiente constitutes the eroded remnants of the depression formed in the northern shield. From 0.65 Ma to present, activity has been restricted to the N-S ridge, which has continued to grow southwards. There was a general N-S migration of volcanic activity with time, but in the shield the trend was northwest to southeast. Eruptive rates seem to have been fairly constant during the different eruptive phases considered, between 0.15 and 0.37 km 3/ka. A very similar succession of constructive and destructive episodes has been obtained for the neighboring island of Hierro, but in this case the activity started around 0.8 Ma and eruptive rates were about 0.5 km 3/ka.

Time correlation by palaeomagnetism of the 1631 eruption of Mount Vesuvius. Volcanological and volcanic hazard implications

The 1631 eruption of Mount Vesuvius was the most destructive episode in the recent volcanic history of Vesuvius and the last in which large pyroclastic flows were emitted. The controversy about whether lava flows were also generated in this eruption, as sustained in the mapping by Le Hon (1866) and by the interpretation by some authors (Burri et al., 1975; Rolandi et al., 1991) of eyewitness accounts, is important not only for a better understanding of the eruption but also for the implications in the prediction of volcanic hazards of this volcano, set in an overpopulated area with more than 3 million people potentially at risk. Short-period palaeomagnetic techniques (secular variation curve) have been applied to correlate lava flows interpreted as produced in the event of 1631 with the pyroclastic flow of this same eruption and other lava flows unquestionably emitted prior to this eruptive event. The model that best fits the results obtained suggests that the presumed 1631 lava flows were not the result of a single eruptive event but were, in fact, produced by several different eruptions. These lava flows also have a better palaeomagnetic correlation with the medieval lava flows than with the pyroclastic flow of 1631, whose juvenile pumice clasts have a well-defined single component magnetization that fits in the expected corresponding position of the secular variation curve for that age. The palaeomagnetic characteristics of the 1631 pyroclastic flow are compatible with a “hot” depositional temperature (apparently above the Curie point of magnetite, 585 °C) for the juvenile pumice fragments (magmatic fraction) and a “cold” deposition for the non-magmatic fraction. This suggests the lack of thermal equilibration during transport of the larger clasts, probably due to the short distance travelled by the pyroclastic flows. The main volcanological and volcanic hazard issues of this work are that the 1631 event was entirely explosive and that pyroclastic flow activity played a major role in the eruption. Before 1631 Vesuvius remained for about five centuries in a state of quiescence. If the present period of repose continues for decades or centuries it is increasingly likely that the next eruption will be a highly dangerous explosive event similar to that of 1631.

ENERGY INTENSITY IMPROVEMENTS IN STEEL MINIMILLS

Over the past 20 years, U.S. steel manufacturing has experienced an episode of creative destruction. Iron‐ore based plants closed, and new electric arc furnace (EAF) plants–the “minimills”–opened. The steel industry is an energy intensive segment of manufacturing, and the changeover causes major change in energy use. The analysis here links a plant‐level database from the Bureau of the Census with publicly available sources and obtains measures of the best practice energy use in minimills. The analysis examines how technical efficiency, vintage, and capacity utilization affect plant‐level electricity use per ton of steel. This measure of electricity use gives a plant's “energy intensity.” Plants in the sample keep operating even during deep recessions, suggesting that energy, e.g., BTU, taxes may fall short of the fullest potential for reducing energy use. During recession, plants actually may continue to operate at lower output rates and higher energy intensities rather than close down. Substantial potential exists for energy improvements of as much as 1 billion kWh per year. New facilities exhibit energy intensity improvement of 6.2 kWh/ton per year. This finding is consistent with engineering estimates. Realizing this potential among all plants would require policies that assist capital turnover.

Chronic adult periodontitis and burst progression may reflect local neutrophil defects due to perivascular hyaline deposits

Chronic adult periodontitis (CAP) is a common disease of the supporting tissues of teeth, and is a major cause of tooth loss. This disease is distinguished from more rare rapidly progressing forms of periodontitis, in which a variety of neutrophilic polymorphonuclear leukocyte (PMN) defects have been identified. PMN dysfunctions have, however, not been observed in CAP. In CAP, destructive episodes of the disease occur sporadically and independently in different parts of the mouth. In this paper, it is proposed that CAP is due to highly localized defects in PMN function. Impaired PMN function is suggested as resulting in the formation of a virulent bacterial plaque, which is capable of initiating periodontal pocket formation. A previously reported perivascular hyaline material may account for localized PMN defects, by reducing the number of PMNs entering affected sites. The proposed model may explain both the presence of CAP in otherwise normal patients, and the sporadic pattern of tissue destruction seen in this disease.

Contrasting lithofacies architecture in ring-plain deposits related to edifice construction and destruction, the Quaternary Stratford and Opunake Formations, Egmont Volcano, New Zealand

The early constructional and destructional history of ancestral Egmont Volcano is recorded by variations in lithofacies assemblages and architecture in volcaniclastic deposits making up the southern ring plain. Eruptive periods and edifice construction are recorded by aggradational sequences of debris-flow deposits on the ring plain and numerous tephra deposits preserved on the lower flanks of the volcano. The aggradational sequences represent fairly long-term periods of accumulation when a succession of lahars delivered coarse-grained sediment to the ring plain. Edifice destruction is recorded on the ring plain by deposits of debris-avalanches and associated debris flows. Individual deposits represent rapid (as much as 2.6 km 3), but episodic, sedimentation over large areas (up to 500 km 2) of the ring plain. Sedimentation following these events was slow, with reworked tephra and lignite accumulating over most of the ring plain. Episodes of edifice destruction usually marked the beginning of long-term quiescent intervals or periods of low-frequency eruptive activity. Tephra deposits on the flanks of the volcano are not as abundant as in stratigraphic intervals representing periods of edifice construction.

Specific antibody responses to subgingival plaque bacteria as aids to the diagnosis and prognosis of destructive periodontitis*

We have reviewed the recent literature on the humoral immune responses to a variety of subgingival plaque bacterial species in patients with destructive periodontal diseases. We do not feel that the information presently available on the specific antibody responses to proposed pathogens such as Bacteroides gingivalis and Actinobacillus actinomycetemcomitans allows antibody responses to be diagnostic. All control subjects without periodontal destruction have antibodies to candidate pathogens but the generally higher levels in patients are not sufficiently elevated to be diagnostic. Nor can they be used to predict the initiation of disease or the onset of new episodes of destruction where disease had previously occurred. Successful treatment of patients may lead to lower levels of antibodies to some organisms, including possible pathogens, and thus support a given species in the aetiopathogenesis of disease. It appears that unsuccessful treatment may be accompanied by continuing high antibody levels to some organisms and further studies may enable this observation to be used to monitor therapy. There is some evidence from serological studies that each destructive episode may be induced by a different bacterial species or consortium. The start of studies using single antigens and the techniques of molecular biology will provide not only antibody-based diagnostic methods but also allow us to determine which bacterial antigens are virulence factors and thus the role of the antibody responses, whether protective or damaging, in the periodontal diseases.

Volcanic evolution of the island of Tenerife (Canary Islands) in the light of new K-Ar data

New age determinations from Tenerife, together with those previously published (93 in all), provide a fairly comprehensive picture of the volcanic evolution of the island. The oldest volcanic series, with ages starting in the late Miocene, are formed mainly by basalts with some trachytes and phonolites which appear in Anaga, Teno and Roque del Conde massifs. In Anaga (NE), three volcanic cycles occurred: one older than 6.5 Ma, a second one between 6.5 and 4.5 Ma, with a possible gap between 5.4 and 4.8 Ma, and a late cycle around 3.6 Ma. In Teno (NW), after some undated units, the activity took place between 6.7 and 4.5 Ma, with two main series separated by a possible pause between 6.2 and 5.6 Ma. In the zone of Roque del Conde (S), the ages are scattered between 11.6 and 3.5 Ma. Between 3.3 and 1.9 Ma, the whole island underwent a period of volcanic quiescence and erosion. The large Cañadas volcano, made up of basalts, trachytes and phonolites, was built essentially between 1.9 and 0.2 Ma. To the NE of this central volcano, linking it with Anaga, is a chain of basaltic emission centers, with a peak of activity around 0.8 Ma. The Cañadas Caldera had several collapse phases, associated with large ignimbrite emissions. There were, at least, an older phase more than 1 Ma old, on the western part of the volcano, and a younger one, less than 0.6 Ma old, in the eastern side. The two large “valleys” of Guimar and la Orotava were formed by large landslides less than 0.8 Ma ago, and probably before 0.6 Ma ago. The present Cañadas caldera was formed by another landslide, less than 0.2 Ma ago. This caldera was later filled by the huge Teide volcano, which has been active even in historic times. During the same period a series of small volcanoes erupted at scattered locations throughout the island. The average eruptive rate in Tenerife was 0.3 km 3/ka, with relatively small variations for the different eruptive periods. This island and La Gomera represent a model of growth by discontinuous pulses of volcanic activity, separated by gaps often coinciding with episodes of destruction of the edifices and sometimes extended for several million years. The neighbouring Gran Canaria, on the other hand, had an initial, rapid “shield-building phase” during which more than 90% of the island was built, and a series of smaller pulses at a much later period. A comparison between these three central islands indicates that the previously postulated westward displacement in time of a gap in the volcanic activity is valid only as a first approximation. Several gaps are present on each island, overlapping in time and not clearly supporting either of the models proposed to explain the evolution of the Canaries.

Erg deposits in the Lower Jurassic Wingate Sandstone, northeastern Arizona: oblique dune sedimentation

ABSTRACTThe Lower Jurassic erg (aeolian sand sea) deposits of the Wingate Sandstone on the Colorado Plateau are beautifully exposed near Many Farms, Arizona. These 3‐D outcrops allow a detailed study of structures and sequenses in the erg body.The erg sequence comprises chiefly oblique dune deposits. The dune facies are in most cases characterized by a well‐developed tripartite upbuilding. Each dune coset contains unusually thick and intricate bottomsets, medial low‐angle dipping toesets, and upper steeply dipping foresets.The foresets reveal significant across‐crest transport of sand and dip within a narrow range of directions towards the ESE. The bottomset beds are composed of compound cross‐bedding that documents strong along‐crest transport towards the SSW, whereas the toeset beds reveal upslope, downslope, and along‐crest transport of sand.The ancient dunes apparently formed in a directionally varying wind flow with prevailing winds (early summer) from the NW and periodic strong winds (late summer) from the SW. The dunes were oblique not only to seasonal transport directions, but also to the resultant annual transport direction and dune migration direction. This was caused by the interaction of the dune system with the primary winds which resulted in secondary airflow and significant along‐crest transport of sand.The erg deposits at Many Farms are separated by a number of super bounding surfaces suggesting several episodes of erg formation and destruction. The initial erg system was dominated by transverse dunes, but overlying ergs only contained oblique dunes. All erg systems were bounded to the SW by wide regions of erg margin environments in which aeolian sand sheet, fluvial, and lacustrine facies were deposited. Even though fluvial deposits are absent from the main part of the sequence at the study area, the effects of this system are reflected within the erg deposits at Many Farms.

Considering the Source: Testimony versus Data in Regulations Surrounding Gulf and South Atlantic Trap Fisheries

The source of a problem influences the source of information we use to address the problem. However, the source of information we use can also influence our conceptualization of the problem. Just such a paradox faces fishermen in the Gulf and South Atlantic trap fisheries. Competition and conflict among commercial trap fishermen, other types of fishermen (e.g., longliners and divers), recreational fishermen, and environmentalists occur throughout South Atlantic and Gulf waters, yet an actual accounting of episodes of environmental destruction, theft of traps, and so on, has been difficult to develop. In many cases, documentation has become largely irrelevant. People perceive theft, destruction, or resource depletion to be occurring, and the strength of their belief prompts them to political organization and action. Using information from North Carolina, the Caribbean, and the Florida Keys, this article discusses the ways in which various sources of information have influenced the management of trap fisheries in the South Atlantic and Gulf of Mexico waters. Implications for other policy domains are discussed, [fisheries, regulation, testimony, science, farming systems, natural resources]

The role of dental plaque in gingivitis and periodontitis.

A dynamic equilibrium between the periodontal microbiota and the host generally results in a clinical state of periodontal health, characterized by minimal inflammatory changes in the marginal gingival tissues. Maintenance of health is most easily achieved by controlling the resident mass of bacteria. In rare instances, control of specific microorganisms may be indicated. Lack of microbial control may lead to an imbalance between the microbiota and the host due to a markedly increased microbial mass and/or increased virulence of the micro-organisms present. Such alterations in the host-parasite equilibrium may result in transient episodes of tissue destruction and, in the long term, to cumulative damage to the periodontal tissues.

Eruptive history of the Colima volcanic complex (Mexico)

The evolution of the Colima volcanic complex can be divided into successive periods characterized by different dynamic and magmatic processes: emission of andesitic to dacitic lava flows, acid-ash and pumice-flow deposits, fallback nuées ardentes leading to pyroclastic flows with heterogeneous magma, plinian air-fall deposits, scoriae cones of alkaline and calc-alkaline nature. Four caldera-forming events, resulting either from major ignimbrite outbursts or Mount St. Helens-type eruptions, separate the main stages of development of the complex from the building of an ancient shield volcano (25 × 30 km wide) up to two summit cones, Nevado and Fuego. The oldest caldera, C1 (7–8 km wide), related to the pouring out of dacitic ash flows, marks the transition between two periods of activity in the primitive edifice called Nevado I: the first one, which is at least 0.6 m.y. old, was mainly andesitic and effusive, whereas the second one was characterized by extrusion of domes and related pyroclastic products. A small summit caldera, C2 (3–3.5 km wide), ended the evolution of Nevado I. Two modern volcanoes then began to grow. The building of the Nevado II started about 200,000 y. ago. It settled into the C2 caldera and partially overflowed it. The other volcano, here called Paleofuego, was progressively built on the southern side of the former Nevado I. Some of its flows are 50,000 y. old, but the age of its first outbursts is not known. However, it is younger than Nevado II. These two modern volcanoes had similar evolutions. Each of them was affected by a huge Mount St. Helens-type (or Bezymianny-type) event, 10,000 y. ago for the Paleofuego, and hardly older for the Nevado II. The landslides were responsible for two horseshoe-shaped avalanche calderas, C3 (Nevado) and C4 (Paleofuego), each 4–5 km wide, opening towards the east and the south. In both cases, the activity following these events was highly explosive and produced thick air-fall deposits around the summit craters. The Nevado III, formed by thick andesitic flows, is located close to the southwestern rim of the C3 caldera. It was a small and short-lived cone. Volcan de Fuego, located at the center of the C4 caldera, is nearly 1500 m high. Its activity is characterized by an alternation of long stages of growth by flows and short destructive episodes related to violent outbursts producing pyroclastic flows with heterogeneous magma and plinian air falls. The evolution of the primitive volcano followed a similar pattern leading to formation of C1 and then C2. The analogy between the evolutions of the two modern volcanoes (Nevado II–III; Paleofuego-Fuego) is described. Their vicinity and their contemporaneous growth pose the problem of the existence of a single reservoir, or two independent magmatic chambers, after the evolution of a common structure represented by the primitive volcano.

Preliminary Characterization of a Persistent Infection of HeLa Cells with Human Rhinovirus Type 2

We were able to initiate a persistent infection (PI) in HeLa cells with a temperature-sensitive (ts-) mutant of rhinovirus type 2 (TS-1), but not with the corresponding wildtype (wt) virus. The ability to initiate a PI may be related to the multiplicity of infection. Persistence was established at 37 degrees C but not at 32 degrees C and the virus isolated from the PI was no longer temperature-sensitive. Infectious virus was continually produced at low levels throughout the course of the PI and cell cultures underwent multiple episodes of partial destruction (crisis) and subsequent recovery. PI virus and the initiating virus were neutralized to the same extent by hyperimmune polyclonal TS-1 antiserum indicating that no significant change had occurred with respect to serological type. The presence of either interferon or virus-related interfering activity could not be demonstrated in the PI cultures. Superinfection experiments in cells that were 'cured' of PI virus indicated the selection of a cell population during persistence that could no longer support the growth of homologous-type virus. This effect became less pronounced upon further passage of the cured cells. When compared with the wt and ts viruses, the PI virus yielded comparable amounts of infectious virus in HeLa cells but with decreased synthesis of RNA.