Enthalpies of transfer for proteins from aqueous to water-alcohol solutions: a test for models of residues exposed to solvent

The enthalpies of transfer of proteins from aqueous solution to alcohol–water solutions are used as probes of solvent-accessible surface for these proteins. Enthalpies of transfer to 10 wt% ethanol solutions are determined calorimetrically for the native proteins ribonuclease A, lysozyme, and ovalbumin. Ribonuclease A and lysozyme are reduced and carboxamidomethylated to produce configurations in which interior residues of the native protein are exposed to the solvent; enthalpies of transfer are determined for these species. These data are then compared with enthalpies of transfer for the constituent amino acids of the proteins. The enthalpies of transfer for the residues are used to generate a maximal enthalpy of transfer that can be compared with the enthalpies of transfer for the reduced, carboxamidomethylated proteins. The residue amino acid enthalpies are coupled with probabilities that each residue is an exterior residue to predict an enthalpy of transfer for the native protein that can be compared with the observed enthalpy. The probabilities developed by Wertz and Scheraga and Lee and Richards, and Chothia are then compared on their ability to predict the native enthalpies of transfer for the protein. The Wertz–Scheraga model gives the better fit of this data in all cases.     

Linear rank tests for interval-censored data with application to PCB levels in adipose tissue of transformer repair workers

Linear rank statistics are described for testing for differences between groups when the data are interval-censored. The statistics are closely related to those described by Prentice (1978, Biometrika 65, 167-179) for right-censored data. Problems in calculating the statistics are discussed and several approaches to computation including estimation of the efficient rank scores are described. Results from a small simulation study are presented. The methods are applied to data from a study relating tissue levels of PCBs to occupational exposure.     

Stochastic theory of population genetics

Stochastic models of population genetics are studied with special reference to the biological interest. Mathematical methods are described for treating some simple models and their modifications aimed at the problems of the molecular evolution. Unified theory for treating different quantities is extensively developed and applied to some typical problems of current interest in genetics. Mathematical methods for treating geographically structured populations are given. Approximation formulae and their accuracy are discussed. Some criteria are given for a structured population to behave almost like a panmictic population of the same total size. Some quantities are shown to be independent of the geographical structure and their dynamics are described.     

Estimatingdendroctonus frontalis (Coleoptera: Scolytidae) daily infestation dynamics

Summary Mathematical procedures are given to estimate infestation totals and daily life stage arrivals, departures, and mortality ofDendroctonus frontalis Zimmermann for an infested tree in the field. These estimates are based on minimal sample data and are designed to utilize all available information. Daily arrival estimates for larvae, pupae, and callow adults are obtained by indirect analysis without direct observation of these stages. The procedures are applied to 147 infested trees, and the results are transformed to a common time basis to obtain daily expectations by life stage for an “average” tree. These expectations suggest optimal times for field sampling or relative times of sampling when optimal times are missed. Expected daily arrival distributions by life stage for a single egg and a single attacking adult are given. Procedures are given for utilizing collateral information to obtain an infestation total and daily arrival estimates for a boundary life stage. The results of this study are applicable to anyD. frontalis field study, and the procedures given are applicable to any bark inhabiting insect having similar habits.     

Wood, bark and stem anatomy of New World species of Gnetum

Quantitative and qualitative data are presented for 11 collections of six species. The wide range of character states for the species is presented in the form of a key to emphasize their potential systematic correlations. Distinctive among these are phcllem characteristics. Fibre-tracheids are newly reported for lianoid Gnetum species. Cells previously thought to be like companion cells in secondary phloem are shown to be uniseriate rays, counterparts to uniseriate xylem rays. Laticifers are abundant in most of the species, and are newly described for secondary tissues of Gnetum. Presence of tyloses in laticifers of two species is apparently a new report for vascular plants. Tori are present in two New World Gnetum species, adding to the report in African species. Perforation plates are simple except near or in primary xylem, where they are simple or foraminate. Torus presence and foraminate perforation plate presence are features more reminiscent of Ephedra and other gymnosperms than of angiosperms. The bark of Gnetum is also very similar to that of Ephedra.     

Two-dimensional electrophoresis computerized processing

This paper describes various methods suitable for implementation of two-dimensional processing software. The different steps leading to a complete processing are described, from the digitalization of the image to the processing of the resulting data. The characteristics of a convenient digitalization system are discussed. The different software devoted to spot detection is reviewed with respect to the presence or otherwise of a spot model and its characteristics. The major techniques for gel matching are compared as are designs for database structures suitable for tabulation of measurements. Finally, the need for a sophisticated system of data processing is stressed and its main requirements are described.     

Cell surface proteins and malignant transformation

Many of the altered properties of malignant cells are thought to involve alterations in cell surface functions. In order to understand these alterations it is necessary to know more about the molecular structure of the surface. Methods for analyzing surface proteins are discussed and their application to normal and transformed tissue culture cells are reviewed. A number of surface proteins are observed to be altered by transformation. Most of the alterations are reductions in amounts of particular species, although a few proteins do increase. Evidence concerning the reasons for these alterations and the possible functions of some of the molecules is reviewed. Working hypotheses arising from these data are presented and prospects for understanding the physiological changes in terms of molecular effects are discussed. Particular emphasis is placed on the idea that surface molecules are associated in specific-non-covalent complexes which are important for their functions.     

Uniform persistence and permanence for non-autonomous semiflows in population biology

Conditions are presented for uniform strong persistence of non-autonomous semiflows, taking uniform weak persistence for granted. Turning the idea of persistence upside down, conditions are derived for non-autonomous semiflows to be point-dissipative. These results are applied to time-heterogeneous models of S-I-R-S type for the spread of infectious childhood diseases. If some of the parameter functions are asymptotically almost periodic, an almost sharp threshold result is obtained for uniform strong endemicity versus extinction in terms of asymptotic time averages. Applications are also presented to scalar retarded functional differential equations modeling one species population growth.     

Linear regression analysis of censored medical costs

This paper deals with the problem of linear regression for medical cost data when some study subjects are not followed for the full duration of interest so that their total costs are unknown. Standard survival analysis techniques are ill-suited to this type of censoring. The familiar normal equations for the least-squares estimation are modified in several ways to properly account for the incompleteness of the data. The resulting estimators are shown to be consistent and asymptotically normal with easily estimated variance-covariance matrices. The proposed methodology can be used when the cost database contains only the total costs for those with complete follow-up. More efficient estimators are available when the cost data are recorded in multiple time intervals. A study on the medical cost for ovarian cancer is presented.     

Optimal approximate conversions of odds ratios and hazard ratios to risk ratios

Odds ratios approximate risk ratios when the outcome under consideration is rare but can diverge substantially from risk ratios when the outcome is common. In this paper, we derive optimal analytic conversions of odds ratios and hazard ratios to risk ratios that are minimax for the bias ratio when outcome probabilities are specified to fall in any fixed interval. The results for hazard ratios are derived under a proportional hazard assumption for the exposure. For outcome probabilities specified to lie in symmetric intervals centered around 0.5, it is shown that the square-root transformation of the odds ratio is the optimal minimax conversion for the risk ratio. General results for any nonsymmetric interval are given both for odds ratio and for hazard ratio conversions. The results are principally useful when odds ratios or hazard ratios are reported in papers, and the reader does not have access to the data or to information about the overall outcome prevalence.     

Martian environment and life]

Five conditions for life to arise are discussed with referring to early Martian environment. The key to determine whether any life form appeared on Mars is found to be the early Martian carbon dioxide atmospheric pressure and then the temperature. The importance to determine the heat flow is indicated. The items to be measured for future Martian exploration are listed. The surface materials, which has been poorly understood, are emphasized for further exploration. Two strategies for search for life on Mars, "step by step" strategy and quick strategy, are suggested.     

Strategies for computer modeling

Modeling is a ubiquitous and often misunderstood enterprise in which data from diverse disciplines are analyzed by techniques from other diverse disciplines in an attempt to confirm or falsify a set of hypotheses about the real world. Guidelines are offered for designing models to match the goals of modeling biological systems. Techniques for the construction and interpretation of models are discussed. The requirements for credibility of models are detailed, and tests are suggested for their validation.     

An analytical model for designing yard layouts of a straddle carrier based container terminal

In designing a yard layout for a container terminal several decisions have to be made. In this paper we propose a model which provides decision support for the design of yard layouts of terminals at which straddle carrier are used. We assume that straddle carriers are used for the horizontal transport and the stacking of containers. For the proposed model we develop estimates for the expected cycle distances of straddle carriers. In this case, we distinguish between cycles to landside facilities and to the quay. Numerical results are presented for several parameter settings. For instance, we present results for a comparison of layouts where the rows in the block are orientated parallel with layouts where the rows are orientated perpendicularly to the quay.     

Comparative biogeography of mammals on islands

Insular faunas of terrestrial mammals and bats are examined on a worldwide basis to test the adequacy of equilibrium and historical legacy models as explanations for species-area relationships. Species numbers of bats on islands conform to predictions from equilibrium theory, whereby recurrent immigrations and extinctions influence species richness. By contrast, species numbers of terrestrial mammals on islands result from a historical legacy of very low immigration rates on oceanic islands (the faunas are colonization-limited) and by the fragmentation of once contiguous continental faunas to form relictual populations, which subsequently undergo extinctions, on landbridge islands (the faunas are extinction-limited). This explanation is supported by several lines of evidence: (1) z values (slopes of species-area curves) are lower for non-volant mammals on oceanic islands than for those on landbridge islands, but are the opposite for bats; (2) z values for non-volant mammals are lower than those for bats on oceanic islands, but are higher than those for bats on landbridge islands; and (3) landbridge island faunas are attenuated mainland faunas, whereas those on oceanic islands are ecologically incomplete. No support is found for alternative hypotheses to explain low species-area slopes for terrestrial mammals on oceanic islands.     

Food waste valorization via anaerobic processes: a review

The increasing production of food waste worldwide and new international regulations call for the development of new technologies to treat this biowaste. Anaerobic processes are able to treat efficiently organic wastes, producing at the same time different value-added compounds. In addition, due to the lower costs and environmental impacts associated with these processes when compared to other options, they are among the most promising technologies for food waste treatment. This article reviews the state-of-the-art dealing with treatment of food waste by anaerobic processes, with emphasis on the most recent research carried out. The different processes that are assessed are anaerobic digestion for methane production, anaerobic fermentation for hydrogen and/or volatile fatty acids production and 2-stage systems. The primary issues associated with each alternative are presented, paying special attention to accumulation of ammonia and volatile fatty acids in the reactor. In addition, the latest developments to overcome the complications of each system are also described, focusing on how they improve its stability and performance. Moreover, the relevant economic and environmental research has also been reviewed, including several life cycle analyses that compare anaerobic processes with other technologies used for food waste treatment. Different case studies are also presented. Finally, recommendations for future research for the anaerobic processes studied and options for process integration are discussed. Moving towards the idea of a circular economy, a potential biorefinery for food waste valorization is also proposed.     

Biotope prioritisation in the Central Apennines (Italy): species rarity and cross-taxon congruence

The conservation status of invertebrates is usually lesser known than that of vertebrates, and strategies to identify biotopes to preserve invertebrate diversity are typically based on a single surrogate taxon, or even on the use of vertebrates as surrogates. Aim of this research is to illustrate a method for biotope prioritisation that can be easily adapted to different animal groups and geographical contexts. A two-step protocol for biotope prioritisation is proposed on the basis of a multidimensional characterisation of species vulnerability. Firstly, species vulnerability is estimated from rarity measures which include geographical range, abundance and biotope specialisation. Then, these values of vulnerability are used to rank biotopes. The method was applied here to the tenebrionid beetles, the butterflies, the birds and the mammals of the Central Apennines, a montane area of high conservation concern for South Europe. This study provides evidence for the importance of including insects in conservation decisions, because vertebrates are poor surrogates for insects. Conservation efforts in the reserves included in the study area are mostly focused on vertebrates, for which woodlands are considered particularly important. However high altitude open biotopes are crucial for both tenebrionids and butterflies, and preservation of such kind of biotopes would be beneficial also for vertebrates. The approach applied here demonstrates that (1) vertebrates are poor surrogates for insects, and (2) measures of species rarity, typically used in vertebrate conservation, can be obtained also for insects, for which a veritable amount of data are hidden in specialised literature and museum collections.     

The application of SIMS to nutrient tracer studies in plant physiology

Current controversies in root physiology relating to the uptake and translocation of mineral nutrients are presented. The opportunities for a SIMS contribution to resolve these controversies are discussed for each of the stable isotope tracers relevant to plant nutrition. It is concluded that for all major nutrients except phosphorus there are promising stable isotope tracers. At the same time, there are challenges to overcome in each case, with respect to background levels, peak interferences and sometimes sensitivity. Techniques of tissue preparation and handling are discussed in some detail, giving attention to the special requirements of plant tissue preparation and analysis for diffusable ions. It is suggested that adapting a preparation and transfer system, designed for production of bulk frozen-hydrated cryofractured specimens, to a secondary ion mass spectrometer would permit easy, rapid preparation. Additionally, this preparation minimizes several serious technical problems inherent to other preparative methods. Difficulties in quantitation are treated briefly, outlining some difficulties specific to plant tissue analysis. Prospects for future applications in plant mineral nutrition are evaluated, taking into account current instrumental developments.     

Conflict and cooperation among the Vikings: Contingent behavioral decisions

We analyze historical accounts of Viking populations in Scotland and Iceland to show that considerations of kinship play a role in individuals' decisions on whether to engage in and revenge murder, as well as in the formation of alliances. However, willingness to murder a relative or to demand vengeance for the murder of another individual depends on the costs and benefits that accrue from the action, as well as the degree of relatedness. When the potential gains from murder are high, individuals are more willing to murder relatives; when the costs of exacting vengeance for a murder are high, individuals are more likely to settle for blood-money compensation for the murder of a family member. Alliances are more likely to be formed with relatives than between unrelated families; moreover, alliances with related individuals are less likely to involve preconditions and are more likely to be stable in the long term.