bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geological Aspects of High-Pressure Research
Authors: Boyd F. R. 
Published: October 2006

The low-density minerals that make up the bulk of rocks in the earth's crust, such as quartz and the feldspars, are transformed by high pressure into much denser phases. In some cases the products of these transitions are new phases that were first discovered in the laboratory; in other cases they are minerals such as kyanite, jadeite, and pyrope, which have long been known as constituents of metamorphic rocks. Determinations of the stability fields of these high-pressure minerals show that either metamorphism of sedimentary rocks takes place at much greater depth than has hitherto been supposed or pressures generated by orogenic forces may have significantly augmented the hydrostatic pressure. The second alternative seems unlikely, but lack of information on the strength of rocks during metamorphism makes the matter uncertain.
Geophysical and petrological observations indicate that the dominant rock type in the upper mantle is garnet peridotite. However, there is reason to believe that the mantle is inhomogeneous and that a variety of rocks ranging in bulk composition from eclogite to peridotite are present. Hydrous phases, such as amphiboles, are possible constituents in the upper 100 kilometers. The hypothesis that the Mohorovičić discontinuity is a dynamic equilibrium between basalt and eclogite seems improbable.

The transition zone between the upper and lower mantle can be explained as a series of reactions in which silicates with the silicon ion in fourfold coordination are transformed into phases in which silicon is in six-fold coordination. This interpretation is supported by synthesis of stishovite, a polymorph of SiO
2
with rutile structure, and by syntheses of germanate pyroxenes with ilmenite structure.

Data on the melting of silicates at pressures up to 50 kilobars show that the initial d
T
/d
P
slopes of silicate melting curves are much steeper than those of metals but that they show considerable curvature. The increase of melting temperature with pressure should be much more pronounced near the top of the mantle than at greater depth.
Distribution of Wild Wheats and Barley
Authors: Harlan Jack R. , Zohary Daniel 
Published: October 2006

If we accept the evidence at face value, we are led to conclude that emmer was probably domesticated in the upper Jordan watershed and that einkorn was domesticated in southeast Turkey. Barley could have been domesticated almost anywhere within the arc bordering the fertile crescent. All three cereals may well have been harvested in the wild state throughout their regions of adaptation long before actual farming began. The primary habitats for barley, however, are not the same as those for the wheats. Wild barley is more xerophytic and extends farther downslope and into the steppes and deserts along the wadis. It seems likely that, while all three early cereals were domesticated within an are flanking the fertile crescent, each was domesticated in a different subregion of the zone.
Lest anyone should be led to think the problem is solved, we wish to close with a caveat. Domestication may not have taken place where the wild cereals were most abundant. Why should anyone cultivate a cereal where natural stands are as dense as a cultivated field? If wild cereal grasses can be harvested in unlimited quantities, why should anyone bother to till the soil and plant the seed? We suspect that we shall find, when the full story is unfolded, that here and there harvesting of wild cereals lingered on long after some people had learned to farm, and that farming itself may have originated in areas adjacent to, rather than in, the regions of greatest abundance of wild cereals.
We need far more specific information on the climate during incipient domestication and many more carefully conducted excavations of sites in the appropriate time range. The problem is far from solved, but some knowledge of the present distribution of the wild forms should be helpful.
Risk of Thyroid Neoplasms after Irradiation in Childhood
Authors: Hempelmann Louis H. 
Published: October 2006

The incidence of thyroid carcinoma and of clinically palpable thyroid nodules is compared in three groups of individuals many years after exposure to ionizing radiation in childhood or infancy. The estimated mean cumulative doses to the thyroid gland ranged from 20 rad in the Ann Arbor series irradiated with x-rays as infants for thymic enlargement upward to 1225 rad of mixed radiation (including that from ingested radioiodine) in the Marshallese children. Intermediate between these extremes is the high-risk subgroup in the Rochester series of persons irradiated for thymic enlargement; they received an estimated mean thyroid dose of 335 rad.
A plot of the incidence of thyroid nodularity against the total cumulative thyroid dose gives what could be a linear dose response with no threshold or, at least, a threshold below 20 rad. The risk of developing carcinoma in the three studies ranges from 0 to 5.5 cases and that for nodularity 38 to 52 cases per 106 persons exposed per rad (thyroid dose) per year. There is evidence from animal experimentation that the biologically effective dose in the case of the Marshallese would have been considerably lower than the cumulative physical dose; hence, the dose response might actually be curvilinear at least in the higher dose range.
In view of the uncertainties regarding dose and the assumptions made in my study, the risk values may not be exact; however, these values reflect the trends regarding risks estimated from the best available data in man. Furthermore, the estimated risk values apply only if radiation exposure occurred in childhood.
What's Wrong with Plastic Trees?
Authors: Krieger Martin H. 
Published: October 2006

With some ingenuity, a transformation of our attitudes toward preservation of the environment will take place fairly soon. We will recognize the symbolic and social meanings of environments, not just their economic utility; we will emphasize their historical significance as well as the future generations that will use them.At the same time, we must realize that there are things we may not want to trade at all, except in the sense of letting someone else have his share of the environment also. As environments become more differentiated, smaller areas will probably be given greater significance, and it may be possible for more groups to have a share.It is likely that we shall want to apply our technology to the creation of artificial environments. It may be possible to create environments that are evocative of other environments in other times and places. It is possible that, by manipulating memory through the rewriting of history, environments will come to have new meaning. Finally, we may want to create proxy environments by means of substitution and simulation. In order to create substitutes, we must endow new objects with significance by means of advertising and by social practice. Sophistication about differentiation will become very important for appreciating the substitute environments. We may simulate the environment by means of photographs, recordings, models, and perhaps even manipulations in the brain. What we experience in natural environments may actually be more controllable than we imagine. Artificial prairies and wildernesses have been created, and there is no reason to believe that these artificial environments need be unsatisfactory for those who experience them.Rare environments are relative, can be created, are dependent on our knowledge, and are a function of policy, not only tradition. It seems likely that economic arguments will not be sufficient to preserve environments or to suggest how we can create new ones. Rather, conscious choice about what matters, and then a financial and social investment in an effort to create significant experiences and environments, will become a policy alternative available to us.What's wrong with plastic trees? My guess is that there is very little wrong with them. Much more can be done with plastic trees and the like to give most people the feeling that they are experiencing nature. We will have to realize that the way in which we experience nature is conditioned by our society—which more and more is seen to be receptive to responsible interventions.Bentham, the father of utilitarianism, was very concerned about the uses of the dead to the living and suggested:If a country gentleman have rows of trees leading to his dwelling, the autoicons [embalmed bodies in an upright position] of his family might alternate with the trees; copal varnish would protect the face from the effects of rain—caoutchouc [rubber] the habiliments.
Methanol: A Versatile Fuel for Immediate Use
Authors: Reed T. B. , Lerner R. M. 
Published: October 2006

We believe that methanol is the most versatile synthetic fuel available and its use could stretch or eventually substitute for, the disappearing reserves of low-cost petroleum resources. Methanol could be used now as a means for marketing economically the natural gas that is otherwise going to waste in remote locations. If methanol were used as an additive to gasoline at a rate of 5 to 15 percent, for use in internal combustion engines, there would be an immediate reduction in atmospheric pollution, there would be less need for lead in fuel, and automobile performance would be improved.With increasing production of fuel-grade methanol from coal and other sources, we foresee the increasing use of methanol for electrical power plants, for heating, and for other fuel applications. We hope that a practical methanol fuel cell will be commercially available by the time that methanol becomes plentiful for fuel purposes.Methanol offers a particularly attractive form of solar-energy conservation, since agricultural and forest waste products can be used as the starting material. Indeed, at 1 percent conversion efficiency the forest lands could supply the entire present energy requirements of the United States.
Ecological Aspects of Amphibian Metamorphosis
Authors: Wilbur Henry M. , Collins James P. 
Published: October 2006

A synthetic theory of the ecology of amphibian metamorphosis is founded on the observation that the large variation in length of larval period and body size at metamorphosis typical of a particular species of amphibian cannot be directly explained by differences in dates of hatching or egg sizes. It is proposed that as development proceeds, variation in exponential growth coefficients causes a trend from a normal distribution to a skewed distribution of body sizes. The degree of skewing increases and the median of the distribution decreases with increasing initial densities of populations. The relative advantages of the largest members of a cohort may arise from a variety of mechanisms including the production of growth inhibitors, interference competition, and size-selective feeding behavior. These mechanisms result in a nonnormal distribution of competitive ability, a possible source of the density-dependent competition coefficient found in systems with many species.In our model the ranges of body sizes and dates of metamorphosis are determined by a minimum body size that must be obtained and a maximum body size that will not be exceeded at metamorphosis. Between these two size thresholds the endocrinological initiation of metamorphosis is expected to be related to the recent growth history of the individual larva. Species that exploit uncertain environments will have a wide range of possible sizes at metamorphosis. Species exploiting relatively certain environments will have a narrower range. The evolution of neoteny and direct development logically follow from the application of these ideas to the ecological context of the evolution of amphibian life histories. Species that live in constant aquatic habitats surrounded by hostile environments (desert ponds, caves, high-altitude lakes) may evolve permanent larvae genetically incapable of metamorphosis. Other populations may evolve a facultative metamorphosis such that populations are a mixture of neotenes and terrestrial adults. Direct development results from selection to escape the competition, predation, and environmental uncertainty characteristic of some aquatic habitats and is usually accompanied by parental care. The relation between our ecological model and the physiological mechanisms that initiate metamorphosis can only be suggested and it remains an open problem for developmental biologists.
Atmospheric Electrical Detection of Organized Convection
Authors: Markson Ralph 
Published: October 2006

Relatively simple atmospheric electrical instrumentation carried on a small aircraft constitutes a flexible and sensitive system for detecting organized convection. Data can be obtained close to the sea surface, and low-velocity flight enhances the spatial resolution. With a slow-flying airplane or powered glider, it may be possible to trace the circulation of individual convection cells and to investigate the trajectory of air which forms cumulus clouds, one of the major unsolved problems in tropical meteorology. Since space charge near the ocean surface was found on some days to be organized on a horizontal scale equivalent to the cumulus cloud scale, this suggests that some of the air which forms maritime cumulus clouds may come from within a few meters of the ocean and that atmospheric electrical instrumentation may have the potential for tracing air from the sea surface to the clouds.
Although the atmospheric electrical instrumentation technique described here cannot be used for direct measurement of air velocity, it may be possible to develop a model that can be used to calculate air velocities from electric field data. Even though with the technique described here it is not possible to make direct measurements of wind velocity, airborne electric field records can provide useful information about convection by delineating patterns in the wind field and structural features of thermals (rising bodies of relatively warm air) and by making possible the remote detection of thermals.
Future plans include attempting to trace interfaces between adjacent roll vortices from the sea surface through the depth of the mixed layer (i) by flying the aircraft parallel to the wind so as to nullify the horizontal electric field (measured between wing-tip probes) while ascending and descending along the interface between adjacent roll vortices and (ii) by measuring vertical and horizontal potential gradient variations at different flight levels.
The sensitivity of atmospheric electrical instrumentation to the top of the mixed layer and structure within it can be used to explore another important problem in boundary layer convection—why convective cloud cover and oceanic rainfall are greater at night than during the day.
Workers in atmospheric electricity have long recognized that their domain is strongly controlled by turbulence in the lower atmosphere, and many have believed that the most effective use of atmospheric electrical techniques to assist meteorological research would be in studying exchange processes. Reiter effectively extended atmospheric electrical studies of boundary layer phenomena through a height range by mounting instruments on cable cars traveling between the valley floor and mountain tops in the Alps. The airborne measurements described here extend this approach. Relating the electrical structure of the atmosphere to its dynamic structure poses an interesting problem which may contribute to our understanding of the atmosphere.
Modeling the Ice-Age Climate
Authors: Gates W. Lawrence 
Published: October 2006

Using the boundary conditions of sea-surface temperature, ice sheet topography, and surface albedo assembled by CLIMAP for 18,000 B.P., the global ice-age July climate has been simulated with a two-level dynamical atmospheric model. Compared with the simulation for present July climate, the ice age is substantially cooler and drier over the unglaciated continental areas, with the maximum zonal westerlies in the Northern Hemisphere displaced southward in the vicinity of the ice sheets. The simulated changes of surface air temperature agree reasonably well with the estimates available from the analysis of fossil pollen and periglacial data, and are consistent with the simulated changes of other climatic variables. These results are generally supported by independent investigations with simpler models.In spite of this qualified success, further analysis of both simulated and verification data is needed to establish the details of ice-age climate, especially the precipitation regimes, and to document the role of eddy fluxes in maintaining the heat, momentum, and moisture balances of the ice-age general circulation. New paleoclimatic data bases for both July and January of 18,000 B.P. are being assembled by CLIMAP and will be used in new simulations of the seasonal ice-age climate.
The Arctic Mirage and the Early North Atlantic
Authors: Sawatzky H. L. , Lehn W. H. 
Published: October 2006

The arctic mirage is a phenomenon that is common in higher latitudes. It occurs under conditions of pronounced temperature inversion, which impart to the air a refractive capability that may equal or exceed the curvature of the earth. Manifestations of the arctic mirage, though largely forgotten in modern times, are described in the earliest accounts of North Atlantic discovery.
This interdisciplinary investigation, combining historical induction with scientific observation and analysis, has suggested a new interpretation of historical events. We believe that information gleaned from these mirages was vital to Norse navigation and exploration in the North Atlantic. We further contend that the mirage may furnish a logical basis for the pervasive ancient and medieval concept of the flat or saucer-shaped world.
Metal Ions in Enzymes Using Ammonia or Amides
Authors: Dixon Nicholas E. , Gazzola Carlo , Blakeley Robert L. , Zerner Burt 
Published: October 2006

In an attempt to understand the role of nickel in jack bean urease (1), we turned to a variety of other enzymes important in the utilization, production, or transfer of ammonia. We found several, including the L-histidine and L-phenylalanine ammonialyases and some enzymes that utilize glutamine or ammonia in amidotransferase reactions, all of which show evidence for the involvement of as yet unreported transition metal ions in their mechanism of action.
We support the view that catalysis by metalloenzymes may be a reflection of the chemistry of the metal ion itself as a Lewis acid, and that perhaps too much emphasis has been placed on supposed special characteristics (such as strain, "entasis") of the enzyme-metal ion association. In this context, we have discussed the mechanism of catalysis of hydrolysis of specific substrates by carboxypeptidase A, and have returned to urease to examine the role of nickel in its mechanism of action.
The Status of the Gene Map of the Human Chromosomes
Authors: McKusick Victor A. , Ruddle Frank H. 
Published: October 2006

In man, the specific chromosome that carries each of about 210 gene loci is known. These loci include at least one assigned to each chromosome (including the Y), about 110 assigned to specific autosomes, and about 100 to the X chromosome. For many loci, information on regional chromosomal localization is also available. The information comes mainly from studies in families and somatic cell hybrids, as well as an integration of results from the two methods.Knowledge of the chromosome map gives insight into evolution, chromosomal organization in relation to genetic control mechanisms, and the pathogenesis of neoplasms and malformations. Furthermore, it is useful in prenatal or premorbid diagnosis of hereditary diseases.
Do circulating leucocytes and lymphocyte subtypes increase in response to brief exercise in children with and without asthma?
Authors: Schwindt C D , Zaldivar F , Wilson L , Leu S-Y , Wang-Rodriguez J , Mills P J , Cooper D M 
Published: October 2006

Background:Exercise can alter health in children in both beneficial (eg reduced long-term risk of atherosclerosis) and adverse (eg exercise-induced asthma) ways. The mechanisms linking exercise and health are not known, but may rest, partly, on the ability of exercise to increase circulating immune cells. Little is known about the effect of brief exercise, more reflective of naturally occurring patterns of physical activity in children, on immune cell responses.Objectives:To determine whether (1) a 6-min bout of exercise can increase circulating inflammatory cells in healthy children and (2) the effect of brief exercise is greater in children with a history of asthma.Methods:Children with mild–moderate persistent asthma and age-matched controls (n = 14 in each group, mean age 13.6 years) performed a 6-min bout of cycle-ergometer exercise. Spirometry was performed at baseline and after exercise. Blood was drawn before and after exercise, leucocytes were quantified and key lymphocyte cell surface markers were assessed by flow cytometry.Results:Exercise decreased spirometry only in children with asthma, but increased (p<0.001) most types of leucocytes (eg lymphocytes (controls, mean (SD) 1210 (208) cells/μl; children with asthma, 1119 (147) cells/μl) and eosinophils (controls, 104 (22) cells/μl; children with asthma, 88 (20) cells/μl)) to the same degree in both groups. Similarly, exercise increased T helper cells (controls, 248 (60) cells/μl; children with asthma, 232 (53) cells/μl) and most other lymphocyte subtypes tested. By contrast, although basophils (16 (5) cells/μl) and CD4+ CD45RO+ RA+ lymphocytes (19 (4) cells/μl) increased in controls, no increase in these cell types was found in children with asthma.Conclusions:Exercise increased many circulating inflammatory cells in both children with asthma and controls. Circulating inflammatory cells did increase in children with asthma, but not to a greater degree than in controls. In fact, basophils and T helper lymphocyte memory transition cells did not increase in children with asthma, whereas they did increase in controls. Even brief exercise in children and adolescents robustly mobilises circulating immune cells.
Smoking in film in New Zealand: measuring risk exposure
Authors: Gale Jesse , Fry Bridget , Smith Tara , Okawa Ken , Chakrabarti Anannya , Ah-Yen Damien , Yi Jesse , Townsend Simon , Carroll Rebecca , Stockwell Alannah , Sievwright Andrea , Dew Kevin , Thomson George 
Published: October 2006

AbstractBackgroundSmoking in film is a risk factor for smoking uptake in adolescence. This study aimed to quantify exposure to smoking in film received by New Zealand audiences, and evaluate potential interventions to reduce the quantity and impact of this exposure.MethodsThe ten highest-grossing films in New Zealand for 2003 were each analysed independently by two viewers for smoking, smoking references and related imagery. Potential interventions were explored by reviewing relevant New Zealand legislation, and scientific literature.ResultsSeven of the ten films contained at least one tobacco reference, similar to larger film samples. The majority of the 38 tobacco references involved characters smoking, most of whom were male. Smoking was associated with positive character traits, notably rebellion (which may appeal to adolescents). There appeared to be a low threshold for including smoking in film. Legislative or censorship approaches to smoking in film are currently unlikely to succeed. Anti-smoking advertising before films has promise, but experimental research is required to demonstrate cost effectiveness.ConclusionSmoking in film warrants concern from public health advocates. In New Zealand, pre-film anti-smoking advertising appears to be the most promising immediate policy response.