A New Approach to Distinguish Thixotropic and Viscoelastic Phenomena

A novel approach for distinguishing the viscoelastic and thixotropic phenomena of predisturbed and intact networks at short and long timescales of observation was proposed using stress relaxation, creep/recovery, single shear decay, and in-shear structural recovery experiments. The method was able to illustrate the connections patterns of the internal microstructure of hydrocolloids and its alteration over time. To test the universality of the new approach, we studied seven commercial and four emerging hydrocolloids. Moreover, to find out the correlation between the proposed parameters from this approach and the fundamental rheological parameters of the selected hydrocolloids, a principal component analysis (PCA) was employed, which showed an excellent correlation between the parameters of all hydrocolloids in predisturbed and intact states at short and long timescales. This work assumed that two different patterns of linkage connection exist, but the analysis can be extended to more than two connection patterns of linkages.

     

Adhesive Interactions and the Patterning of Nerve Connections: An Experimental and Theoretical Approach

Adhesive interactions have long been proposed to play a centralrole in the patterning of neural structures and their interconnections.Many of these ideas are based upon experiments on the projectionfrom the eye to the optic tectum (the retinotectal projection)in lowervertebrates. In order to test the feasibility of suchproposals, a detailed model, based largely on adhesive interactionsbetween cells, has been developed. Computer simulations of themodelshow that simple adhesive interactions are sufficient toexplain much of the literature on the patterning of the amphibianretinotectal projection. Aspects of the model have been experimetallytested through the use of antibodies to known adhesive molecules.The results of these experiments appear consistent with therole of adhesion in the patterning of the connections and withthe predictions of the model. Although such experiments demonstratethe power of adhesive cell interactions in the patterning ofnerve connections, additional experiments and simulations demonstratethat some other non-adhesive processes may play a role. In particular,the addition of a process that is dependent on the activityof the neurons allows the model to better fit the literature.An activity-dependent competition between neurons for adhesivesites on the target cells appears to be sufficient to play thisrole.     

Modeling the Current-Voltage Characteristics of Charophyte Membranes. II. The Effect of Salinity on Membranes of Lamprothamnium papulosum

Lamprothamnium is a salt-tolerant charophyte that inhabits a broad range of saline environments. The electrical characteristics of Lamprothamnium cell membranes were modeled in environments of different salinity: full seawater (SW), 0.5 SW, 0.4 SW, and 0.2 SW. The cells were voltage-clamped to obtain the I/V (current-voltage) and G/V (conductance-voltage) profiles of the cell membranes. Cells growing at the different salinities exhibited one of three types of I/V profiles (states): pump-, background- and K(+)-states. This study concentrates on the pump- and background-states. Curved (pump-dominated) I/V characteristics were found in cells with resting membrane PDs (potential differences) of -219 +/- 12 mV (in 0.2 SW: 6 cells, 16 profiles), -161 +/- 12 mV (in 0.4 SW: 6 cells, 7 profiles), -151 +/- 12 mV (in 0.5 SW: 6 cells, 12 profiles) and -137 +/- 12 mV (in full SW: 8 cells, 13 profiles). The linear I/V characteristics of the background-state were found in cells with resting PDs of -107 +/- 12 mV (in 0.4 SW: 7 cells, 12 profiles), -108 +/- 12 mV (in 0.5 SW: 7 cells, 10 profiles) and -104 +/- 12 mV (in full SW: 3 cells, 5 profiles). The resting conductance (G) of the cells progressively increased with salinity, from 0.5 S x m(-2) (in 0.2 SW) to 22.0 S x m(-2) (in full SW). The pump peak conductance only rose from 2 S x m(-2) (0.2 SW) to 5 S x m(-2) (full SW), accounting for the increasingly depolarized resting PD observed in cells in more saline media. Upon exposure to hypertonic medium, both the pump and an inward K+ rectifier were stimulated. The modeling of the I/V profiles identified the inward K+ rectifier as an early electrical response to hypertonic challenge.     

毒蘑菇家族

自从采食蘑菇的第一天起毒蘑菇中毒事件就不断的发生,从古至今不知有多少人被毒蘑菇夺去性命？！就是到了科学技术十分发达的今天此类事件也时有发生,从某种意义上讲它已成为我们开发利用蘑菇资源的一     

An Experimental Approach to the Effects of Predictability on Community Structure

This paper considers the effects of different levels of resourcepredictability on niche widths, competition and diversity ina community of three hummingbird species. Three pairs of hypothesesare tested: whether decreasing predictability (a) increasesor decreases niche width, (b) increases or decreases competitionand (c) increases or decreases diversity. The results show thatcomplementary increases and decreases in niche width occur withdecreasing predictability, while competition and diversity decrease,at least with extreme unpredictability. A model, which assumesthe species to have similar resource preferences, and its predictionsare examined. The dominant species, Lampornis clemenciae, excludes a subordinatespecies, Archilochus alexandri, from preferred resources. Thisdefense becomes unprofitable with decreasing predictabilityand Archilochus invades the resources once vigorously defendedby Lampornis. When the spectrum of resources is altered in thedirection of decreasing suitability for both species, Lampornisbecomes even more specialized and sensitive to the effects ofunpredictability. A third species, Eugenes fulgens, steals resourcesundefended by Lampornis. These characteristics seem to be commonto a number of communities in very different taxonomic groups,and characteristic of communities in which species share a commonpreferred resource. The question of how a community organizedwith distinct resource preferences responds to decreasing predictabilityremains open.     

An Eliminativist Approach to Vulnerability

The concept of vulnerability has been subject to numerous different interpretations but accounts are still beset with significant problems as to their adequacy, such as their contentious application or the lack of genuine explanatory role for the concept. The constant failure to provide a compelling conceptual analysis and satisfactory definition leaves the concept open to an eliminativist move whereby we can question whether we need the concept at all. I highlight problems with various kinds of approach and explain why a satisfactory account of vulnerability is unlikely ever to be offered if we wish the concept to play a genuinely explanatory role in bioethical contexts. I outline why an eliminativist position should be taken with regard to this concept in light of these concerns but mitigate some of the severity of this position by arguing that we can still make sense of retaining our widespread use of the term by viewing it as nothing more than a useful pragmatic linguistic device that acts as a marker to draw attention to certain kinds of issue. These issues will be entirely governed by other, better understood ethical concepts and theories.