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Leprosy (Hansen disease), a chronic infectious disease caused by Mycobacterium leprae, primarily affects the peripheral nervous system and involves skin and other tissues (1). Although this disease is generally a [...]

Sponges belonging to the genus Cliona are common inhabitants of many coral reefs, and as bioeroders, they play an important role in the carbonate cycle of the reef. Several Cliona species maintain intracellular populations of dinoflagellate zooxanthellae (i.e., Symbiodinium spp.), which also form symbioses with a variety of other invertebrates and protists (e.g., corals, molluscs, foraminifera). Unlike the case of coral symbioses, however, almost nothing is known of the metabolic interaction between sponges and their zooxanthella symbionts. To assess this interaction, we performed a tracer experiment to follow C and N in the system, performed a reciprocal transplant experiment, and measured the stable carbon isotope ratio of Cliona spp. with and without zooxanthellae to study the influence of environment on the interaction. We found strong evidence of a transfer of C from zooxanthellae to their sponge hosts but no evidence of a transfer of N from sponge to zooxanthellae. We also saw significant influences of the environment on the metabolism of the sponges. Finally, we observed significant differences in carbon metabolism of sponge species with and without symbionts. These data strongly support hypotheses of metabolic integration between zooxanthellae and their sponge host and extend our understanding of basic aspects of benthic-pelagic coupling in shallow-water marine environments., Introduction Symbiotic interactions between marine invertebrates and microorganisms are ubiquitous on coral reefs and span the entire symbiosis spectrum from parasitism through mutualism. Many of these interspecific interactions are difficult [...]

In the course of animal morphogenesis, large-scale cell movements occur, which involve the rearrangement, mutual spreading, and compartmentalization of cell populations in specific configurations. Morphogenetic cell rearrangements such as cell sorting and mutual tissue spreading have been compared with the behaviors of immiscible liquids, which they closely resemble. Based on this similarity, it has been proposed that tissues behave as liquids and possess a characteristic surface tension, which arises as a collective, macroscopic property of groups of mobile, cohering cells. But how are tissue surface tensions generated? Different theories have been proposed to explain how mesoscopic cell properties such as cell-cell adhesion and contractility of cell interfaces may underlie tissue surface tensions. Although recent work suggests that both may be contributors, an explicit model for the dependence of tissue surface tension on these mesoscopic parameters has been missing. Here we show explicitly that the ratio of adhesion to cortical tension determines tissue surface tension. Our minimal model successfully explains the available experimental data and makes predictions, based on the feedback between mechanical energy and geometry, about the shapes of aggregate surface cells, which we verify experimentally. This model indicates that there is a crossover from adhesion dominated to cortical-tension dominated behavior as a function of the ratio between these two quantities. differential adhesion hypothesis | differential interfacial tension hypothesis | mathematical modeling cell aggregate geometry | self-assembly doi/10.1073/pnas.1003743107

[1] Structural and thermochronologic studies of the western margin of the central Andean Plateau show changing styles of deformation through time that give insights into tectonic evolution. In southwest Peru, uplift of the plateau proceeded in several distinct phases. First, NW striking, NE dipping reverse faults accommodated uplift prior to ~14-16 Ma. Subsequent uplift of the plateau relative to the piedmont (between the plateau and the Pacific Ocean) occurred between ~14 and 2.2 Ma and was accommodated by NW striking, SW dipping normal faults and subparallel monoclinal folds. The youngest phase of uplift affected the piedmont region and the plateau margin as a coherent block. Although the uplift magnitude associated with phase 1 is unknown, phases 2 and 3 resulted in at least 2.4-3.0 km of uplift. Up to 1 km of this may have occurred during phase 3. Geodynamic processes occurring in both the continental interior and the subduction zone likely contributed to uplift. Citation: Schildgen, T. F., K. V. Hodges, K. X. Whipple, M. S. Pringle, M. van Soest, and K. Cornell (2009), Late Cenozoic structural and tectonic development of the western margin of the central Andean Plateau in southwest Peru, Tectonics, 28, TC4007, doi: 10.1029/2008TC002403.

Substance abusers have a large number of medical and psychiatric problems, and 70-90% are smokers. The aim of this analysis was to examine the prevalence and correlates of medical and psychiatric problems in this sample of drug dependent patients who were participants in a multi-site study of smoking cessation interventions while engaged in substance abuse treatment. Descriptive analyses showed 72.8% of participants had at least one medical problem at baseline and 64.1% had at least one psychiatric diagnosis. Medical problems correlated strongly with age, smoking severity, and pack-years; psychiatric problems correlated with gender and ethnicity. Smoking cessation treatment was associated with a moderate reduction in the ASI Medical composite score. More research is needed on the possible effects of combined treatment of substance abuse and concurrent medical and psychiatric problems. Offering smoking cessation in conjunction with primary care may be a way to address the health needs of this population.

Nicotine dependence is highly prevalent among drug- and alcohol-dependent patients. A multisite clinical trial of smoking cessation (SC) treatment was performed at outpatient community-based substance abuse rehabilitation programs affiliated with the National Drug Abuse Treatment, Clinical Trials Network. Cigarette smokers (N = 225) from five methadone maintenance programs and two drug and alcohol dependence treatment programs were randomly assigned in a 2:1 ratio to receive either (1) SC treatment as an adjunct to substance abuse treatment-as-usual (TAU) or (2) substance abuse TAU. Smoking cessation treatment consisted of I week of group counseling before the target quit date and 8 weeks of group counseling plus transdermal nicotine patch treatment (21 mg/day for Weeks 1-6 and 14 mg/day for Weeks 7 and 8) after the target quit date. Smoking abstinence rates in SC, 10%-11% during treatment and 5%-6% at the 13- and 26-week follow-up visits, were significantly better than those in TAU during treatment (p < .01). In addition, SC was associated with significantly greater reductions as compared with TAU in cigarettes smoked per day (75% reduction, p < .001), exhaled carbon monoxide levels (p < .001), cigarette craving (p < .05), and nicotine withdrawal (p < .05). Smoking cessation did not differ from TAU on rates of retention in substance abuse treatment, abstinence from primary substance of abuse, and craving for primary substance of abuse. Compliance with SC treatment, moderate at best, was positively associated with smoking abstinence rates. Smoking cessation treatment resulted in significant reductions in daily smoking and modest smoking abstinence rates without having an adverse impact on substance abuse rehabilitation when given concurrently with outpatient substance abuse treatment. Substance abuse treatment programs should not hesitate to implement SC for established patients. Keywords: Smoking cessation; Substance abuse; Nicotine; Craving

We explore canyon incision history of the western margin of the Andean (Altiplano-Puna) plateau in the central Andes as a proxy for surface uplift. (U-Th)/He apatite data show rapid cooling beginning at ca. 9 Ma and continuing to ca. 5.1 Ma in response to incision. A minimum of 1.0 km of incision took place during that interval. The youngest apatite date and a volcanic flow perched 125 m above the present valley floor dated at 2.261 [+ or -] 0.046 Ma ([sup.40]Ar/[sup.39]Ar) show that an additional ~1.4 km of incision occurred between ca. 5.1 and 2.3 Ma. Thus, we infer that a total of at least 2.4 km, or 75 % of the present canyon depth was incised after ca. 9 Ma. (U-Th)/He zircon data collected along the same transect imply that the western margin of the plateau was warped upward into its present monoclinal form, rather than uplift being accommodated on major surface-breaking faults. Keywords: Altiplano, geochronology, tectonics, Peru, geomorphology, helium.

This article examines the variables associated with the presence of smoking cessation interventions in drug abuse treatment units, as well as staff attitudes toward the integration of smoking cessation services as a component of care. Surveys were administered to 106 organizations, 348 treatment clinics, and 3,786 employees in agencies that participated in the National Drug Abuse Treatment Clinical Trials Network. Organizational factors, attributes of the treatment setting, and staff attitudes toward smoking cessation treatment were assessed. Use of smoking cessation interventions was associated with the number of additional services offered at clinics, residential detoxification services, and attitudes of the staff toward smoking cessation treatment. Staff attitudes toward integrating smoking cessation services in drug treatment were influenced by the number of pregnant women admitted, the number of ancillary services provided, the attitudes of staff toward evidence-based practices, and whether smoking cessation treatment was offered as a component of care. Keywords: Attitudes; Smoking cessation treatment; Drug abuse clinics

A goal for the validation of computational electromagnetics (CEM) is to provide the community with a simple computational method that can be used to predict the assessment of electromagnetic compatibility (EMC) data as it would be undertaken by individuals or teams of engineers. The benefits of being able to do this include quantifying the comparison of data that has hitherto only been assessed qualitatively, to provide the ability to track differences between model iterations, and to provide a means of capturing the variability and range of opinions of groups and teams of workers. The feature selective validation (FSV) technique shows great promise for achieving this goal. This paper presents a detailed analysis of the FSV method, setting it firmly in the context of previous comparison techniques; it suggests the relationship between validation of graphically presented data and the psychology of visual perception. A set of applicability tests to judge the effectiveness of computer-based CEM validation techniques is also proposed. This paper is followed by a detailed comparison with visual assessment, which is presented in Part II. Index Terms--Computational electromagnetics (CEM), feature selective validation (FSV), validation.

The effect of increasing dose and subsequent annealing on activation and diffusion of boron in Ge is examined. It is found that very high fraction of boron dose can be incorporated substitutionally, immediately after implantation leading to very high hole concentrations, deduced from spreading resistance profiling (SRP).

Phytoplankton and bacterial abundance, size-fractionated phytoplankton chlorophyll-a (Chl-a) and production together with bacterial production, microbial oxygen production and respiration rates were measured. It was found that picophytoplankton were the main contributors to both Chl-a biomass and primary production throughout the region.

Author(s): Brad S. Singer (corresponding author) [1]; Kenneth A. Hoffman [2]; Robert S. Coe [3]; Laurie L. Brown [4]; Brian R. Jicha [1]; Malcolm S. Pringle [5]; Annick Chauvin [6] [...]

The differential adhesion hypothesis (DAH), advanced in the 1960s, proposed that the liquid-like tissue-spreading and cell segregation phenomena of development arise from tissue surface tensions that in turn arise from differences in intercellular adhesiveness. Our earlier measurements of liquid-like cell aggregate surface tensions have shown that, without exception, a cell aggregate of lower surface tension tends to envelop one of higher surface tension to which it adheres. We here measure the surface tensions of L cell aggregates transfected to express N-, P- or E-cadherin in varied, measured amounts. We report that in these aggregates, in which cadherins are essentially the only cell cell adhesion molecules, the aggregate surface tensions are a direct, linear function of cadherin expression level. Taken together with our earlier results, the conclusion follows that the liquid-like morphogenetic cell and tissue rearrangements of cell sorting, tissue spreading and segregation represent self-assembly processes guided by the diminution of adhesive-free energy as cells tend to maximize their mutual binding. This conclusion relates to the physics governing these morphogenetic phenomena and applies independently of issues such as the specificities of intercellular adhesives. Keywords: Cadherins; Cell-cell adhesion; Cell binding energy; Tissue affinities; Differential adhesion; Sorting-out; Cell sorting; Tissue spreading; Surface tension

[1] The Indus River is the only major drainage in the western Himalaya and delivers a long geological record of continental erosion to the Arabian Sea, which may be deciphered and used to reconstruct orogenic growth if the modern bedload can be related to the mountains. In this study we collected thermochronologic data from river sediment collected near the modern delta. U-Pb ages of zircons spanning 3 Gyr show that only ~5% of the eroding .crust has been generated since India-Asia collision.' The Greater Himalaya are the major source of zircons, with additional contributions from the Karakoram and Lesser Himalaya. The [sup.39]Ar/[sup.40]Ar dating of muscovites gives ages that cluster between 10 and 25 Ma, differing from those recorded in the Bengal Fan. Biotite ages are generally younger, ranging 0-15 Ma. Modern average exhumation rates are estimated at ~0.6 km/m.y. or less, and have slowed progressively since the early Miocene (~20 Ma), although fission track (FT) dating of apatites may indicate a recent moderate acceleration in rates since the Pliocene (~1.0 km/m.y.) driven by climate change. The [sup.39]Ar/[sup.40]Ar and FT techniques emphasize the dominance of high topography in controlling the erosional flux to the ocean. Localized regions of tectonically driven, very rapid exhumation (e.g., Nanga Parbat, S. Karakoram metamorphic domes) do not dominate the erosional record. INDEX TERMS: 8102 Tectonophysics: Continental contractional orogenic belts; 1625 Global Change: Geomorphology and weathering (1824, 1886); 1094 Geochemistry: Instruments and techniques; 1035 Geochemistry: Geochronology; 9320 Information Related to Geographic Region: Asia; KEYWORDS: Himalaya, Indus River, fission track, exhumation, erosion, thermochronology. Citation: Clift, P. D., I. H. Campbell, M. S. Pringle, A. Carter, X. Zhang, K. V. Hodges, A. A. Khan, and C. M. Allen (2004), Thermochronology of the modern Indus River bedload: New insight into the controls on the marine stratigraphic record.

It is widely held that segregation of tissues expressing different cadherins results from cadherin-subtype-specific binding specificities. This belief is based largely upon assays in which cells expressing different cadherin subtypes aggregate separately when shaken in suspension. In various combinations of L cells expressing NCAM, E-, P-, N-, R-, or B-cadherin, coaggregation occurred when shear forces were low or absent but could be selectively inhibited by high shear forces. Cells expressing P- vs E-cadherin coaggregated and then demixed, one population enveloping the other completely. To distinguish whether this demixing was due to differences in cadherin affinities or expression levels, the latter were varied systematically. Cells expressing either cadherin at a lower level became the enveloping layer, as predicted by the Differential Adhesion Hypothesis. However, when cadherin expression levels were equalized, cells expressing P- vs E-cadherin remained intermixed. In this combination, 'homocadherin' (E-E; P-P) and 'heterocadherin' (E-P) adhesions must therefore be of similar strength. Cells expressing R- vs B-cadherin coaggregated but demixed to produce configurations of incomplete envelopment. This signifies that R- to B-cadherin adhesions must be weaker than either 'homocadherin' adhesion. Together, cadherin quantity and affinity control tissue segregation and assembly through specification of the relative intensities of mature cell-cell adhesions. Keywords: Cadherin; Cell adhesion; Cell affinity; Cell sorting; Differential adhesion; Homophilic; Morphogenesis; Segregation; Sorting-out; Specificity

We report on a 1-W injection-locked cw titanium:sapphire ring laser at 846 nm. Single-frequency operation requires only a few milliwatts of injected power. This relatively simple and inexpensive system can be used for watt-level single-frequency lasers across most of the titanium:sapphire gain region. A brief review of injection-locking theory is given, and conclusions based on this theory indicate ways to improve the performance of the system. OCIS codes: 140.4480, 140.3590, 140.3580, 140.3560, 140.3280, 140.2020.

Boxfishes (Teleostei: Ostraciidae) are rigid-body, multi-propulsor swimmers that exhibit unusually small amplitude recoil movements during rectilinear locomotion. Mechanisms producing the smooth swimming trajectories of these fishes are unknown, however. Therefore, we have studied the roles the bony carapaces of these fishes play in generating this dynamic stability. Features of the carapaces of four morphologically distinct species of boxfishes were measured, and anatomically-exact stereolithographic models of the boxfishes were constructed. Flow patterns around each model were investigated using three methods: 1) digital particle image velocimetry (DPIV), 2) pressure distribution measurements, and 3) force balance measurements. Significant differences in both cross-sectional and longitudinal carapace morphology were detected among the four species. However, results from the three interrelated approaches indicate that flow patterns around the various carapaces are remarkably similar. DPIV results revealed that the keels of all boxfishes generate strong longitudinal vortices that vary in strength and position with angle of attack. In areas where attached, concentrated vorticity was detected using DPIV, low pressure also was detected at the carapace surface using pressure sensors. Predictions of the effects of both observed vortical flow patterns and pressure distributions on the carapace were consistent with actual forces and moments measured using the force balance. Most notably, the three complementary experimental approaches consistently indicate that the ventral keels of all boxfishes, and in some species the dorsal keels as well, effectively generate self-correcting forces for pitching motions--a characteristic that is advantageous for the highly variable velocity fields in which these fishes reside.

The transient response of a structure may be obtained directly by solving a problem in the time domain. However, there are certain advantages in obtaining the time-domain waveform from frequency-domain data. Taking samples to characterize the frequency spectrum of a resonant structure with no prior knowledge of its behavior, poses difficulty. There is no foolproof way to determine the sampling resolution that will yield an accurate result while keeping the number of samples to a minimum. We propose a frequency sampling technique using a dynamic adaptive algorithm. The algorithm zeroes in on the resonant peaks without user intervention and computes the samples to the required resolution. The resolution is relaxed where appropriate, to achieve economy of samples. A modified discrete Fourier transfor formula is used to process the nonuniformly spaced frequency data into the time-domain waveform. Computation time is vastly reduced. This technique enables the frequency-domain approach to be used for modeling transients in very high-Q structures accurately. Index Terms--Electromagnetic transient analysis, Fourier transforms, frequency-domain analysis, moment methods, sampling methods.

A recent survey by ASCE showed a major need for rebuilding the critical components of the nation's aging infrastructure, such as roads and water-supply systems. To accomplish this major task, in addition to knowledge of basic civil engineering principles and techniques, future civil engineers need to be aware of the effects of planning, design, and construction on our environment. Specifically, a course needs to be developed for educating future civil engineers on concepts and techniques of protecting our natural resources, and planning for sustainable development and construction in an environmentally friendly manner. Specific topics can include modules on water resources and recycling in construction. The focus should be on teaching applications of new environmentally friendly concepts and techniques through case histories and real-world problems. Continuous evaluation of course content and methods of presentation should be made. The course should instill environmental awareness in the students' minds such that in the future, the environment is considered as much a part of any decision-making process in the practice of civil engineering, as are mathematics or the physical sciences. CE Database keywords: Engineers; Engineering education; Curricula; Environmental issues.

We followed adaptation in experimental microbial populations to inhibitory concentrations of an antimicrobial drug. The evolution of drug resistance was accompanied in all cases by changes in gene expression that persisted in the absence of the drug; the new patterns of gene expression were constitutive. The changes in gene expression occurred in four replicate populations of the pathogenic fungus Candida albicans during 330 generations of evolution in the presence of the antifungal drug fluconazole. Genome-wide expression profiling of over 5,000 ORFs identified 301 whose expression was significantly modulated. Cluster analysis identified three distinct patterns of gene expression underlying adaptation to the drug. One pattern was unique to one population and included up-regulation of the multidrug ATP-binding cassette transporter gene, CDR2. A second pattern occurred at a late stage of adaptation in three populations; for two of these populations profiled earlier in their evolution, a different pattern was observed at an early stage of adaptation. The succession of early- and late-stage patterns of gene expression, both of which include up-regulation of the multidrug major facilitator transporter gene, MDR1, must represent a common program of adaptation to this antifungal drug. The three patterns of gene expression were also identified in fluconazole-resistant clinical isolates, providing further evidence that these patterns represent common programs of adaptation to fluconazole.

Widespread basaltic volcanism occurred in the region of the West Siberian Basin in central Russia during Permo-Triassic times. New [sup.40]Ar/[sup.39]Ar age determinations on plagioclase grains from deep boreholes in the basin reveal that the basalts were erupted 249.4 ± 0.5 million years ago. This is synchronous with the bulk of the Siberian Traps, erupted further east on the Siberian Platform. The age and geochemical data confirm that the West Siberian Basin basalts are part of the Siberian Traps and at [east double the confirmed area of the volcanic province as a whole. The larger area of volcanism strengthens the link between the volcanism and the end-Permian mass extinction., Basaltic magma that erupted simultaneously over large areas of Earth's surface--so-called flood basalts--may have released prodigious volumes of S[O.sub.2], C[O.sub.2], HF, and other gases; hence, it is argued, such an [...]

Studies of the picoautotroph-dominated oligotrophic areas of the Eastern Atlantic Ocean show that plankton community respiration in these regions exceeds gross production. These areas also exhibit greater phytoplankton turnover rates than bacteria turnover rates, and high ratios between heterotrophic and autotrophic biomass.

Malcolm S. Hill (*) Abstract. The goal of the research presented here was to examine phenotypic plasticity exhibited by three morpho-types of the common Caribbean sponge Anthosigmella varians (Duchassaing & [...]

At Elan Bank of the Kerguelen Plateau in the southeast Indian Ocean, Leg 183 of the Ocean Drilling Program recovered clasts of garnet-biotite gneiss in a fluvial conglomerate intercalated with basalt flows. U-Pb and Pb-Pb dates of zircons and monazites in these clasts and an overlying sandstone range from 534 to 2547 Ma, which is much older than the surrounding Indian Ocean seafloor. These dates show that old continental crust resides in the shallow crust of the oceanic Kerguelen Plateau and that the breakup of Gondwana dispersed continental fragments into the nascent Indian Ocean lithosphere. Keywords: Kerguelen Plateau, geochronology, continental crust, Proterozoic, Indian Ocean.

Three surveys compared the accuracy of predictions based on forced-choice and subjective probability scales. The latter produced significantly more accurate election predictions and significantly reduced the percentage of undecided, or 'Don't Know' responses, compared to forced-choice scales in all three surveys. Analysis indicates subjective probability scales decrease sampling error and confirms there is an inherent source of error in traditional forced-choice questions about voting intentions not attributable to sampling error. The results are discussed with respect to (1) sampling and measurement errors in forced-choice and subjective probability scales measuring behavioral intentions, (2) their practical application, and (3) cognitive theory, especially support theory.

There is confusion amongst teachers and administrators about interpreting special education legislation. Federal and state safety standards relating to the science laboratory are evolving and teachers must concentrate on providing access to the best science education for students in a safe, humane and positive learning environment. They need to modify laboratory activities to ensure secure specialized laboratory safety, and improve their knowledge about special needs students.

The structure of the 30S ribosomal subunit is presented, based on an electron-density map at 5.5 A resolution. Double-helical RNA and alpha-helices and Beta sheets of proteins can be identified at this resolution and seven 30S-subunit ribosomal proteins and a large portion of double-stranded RNA helices were fitted into density.

Research is presented on the influence of the deep-sea threshold on body size in marine invertebrates. It is posited that larger size is favored at greater depths due to competitive and metabolic advantages.

Different isomers of the mono-, bi-, and trinuclear metallocyclophanes have different electrochemical properties. This was found in a study of the reactions of (Mo(NO)(tp*)I2) with the xylene-dithiols 1,x-(SCH2)2C6H4. The reactions afforded cyclic dimers and trimers as well as novel monometallocyclophanes. These results represent the first definitive evidence that isomer structure can affect the electrochemical properties of metallomacrocycles of this type.

Ultraviolet radiation has a significant impact on amphibian reproduction. Embryonic mortality rates increased in correlation with exposure to ambient solar ultraviolet-B radiation. Both embryonic development and hatching success were affected. These findings have indications for potential conservation strategies, but more research is needed to determine if radiation affects amphibians at the population level.

Volcanic rifted margins have voluminous magmatic constructions at continent-ocean transitions including thick sequences of flood basalts, dike swarms, and mafic plutons developed in crustal-scale flexures. In the Tertiary East Greenland volcanic rifted margin, upper crustal dilation and flexure were accommodated by extensive faulting, locally pervasive cataclastic deformation, and pseudotachylyte generation. The widespread distribution and large volumes of pseudotachylyte suggest that regional seismogenic faulting was vigorous during rapid crustal subsidence, dike intrusion, and the start of sea-floor spreading.

A novel sensorless speed identifier for real-time application in induction motor drives under steady-state and transient conditions is proposed. It is based on the calculation of rotor slot harmonic (RSH) frequencies using an adaptive digital filter. It outperforms other analog or spectrum-based RSH speed identifiers in terms of accuracy and speed of response. The new identifier measures the speed with less than 0.1% error by processing the stator current on a sample-by-sample basis. It is also capable of tracking speed transients of high slew rates with high accuracy. The authors believe this to be the first effective tracking of RSH's during transients ever reported. The proposed algorithm is computationally very efficient and requires only a single processor for its real-time implementation. Simulated and experimental data were used to validate the algorithm. Index Terms - Induction motor control, sensorless control, speed measurement, vector control.

The morphogenetic properties causing germ-layer spreading and stratification in amphibian gastrulation were called 'tissue affinities' by Holtfreter. The differential adhesion hypothesis (DAH) attributes such liquidlike tissue rearrangements to forces generated by intercellular adhesions within and between the migrating cell populations. This theory predicts that, among the primary germ layers, the cohesiveness of deep ectoderm should be the greatest, that of deep mesoderm should be intermediate, and that of deep endoderm should be the least. Also, the cohesiveness of differentiating neural ectoderm should increase after induction, causing it to internalize and segregate from epidermis. The DAH also explains why the cohesiveness of 'liquid' tissues, whose cells are free to rearrange, should be measurable as tissue surface tensions. Using a specially designed tissue surface tensiometer, we demonstrate that (i) aggregates of Rana pipiens deep germ layers do possess liquid-like surface tensions, (ii) their surface tension values lie in precisely the sequence necessary to account for germ-layer stratification in vitro and in vivo, and (iii) the surface tension of deep ectoderm just underlain by the archenteron roof is twice that of not-yet-underlain deep ectoderm. These measurements provide direct, quantitative evidence that the 'tissue affinities' governing germ-layer flow during early stages of vertebrate morphogenesis are reflected in tissue surface tensions.

'Haydn confessed to me that when he heard Handel's music in London, he was so struck by it that he began his studies all over again as if he had [...]

Researchers have investigated the possibility that serotonergic afferents may play a role in the activity-dependent nonphotic entrainment mechanism in rodents. This work was carried out through the selective lesioning of serotonin terminals within and adjacent to the suprachiasmatic nuclei (SCN) by local microinjection of 5,7-dihydroxytryptamine in mice pretreated with desipramine. It was concluded that serotonergic afferents to the SCN are required for the transduction of a volitional activity-dependent entrainment stimulus.

The impact of surface chemistry and processing environments on the adhesive strength of epoxy-based chip attach adhesives on common leadframe substrates is investigated. Chip attached adhesives are bonded to various surfaces under isothermal conditions. Cure temperature was found to influence the gelation time of the epoxy resin and the development of cure stresses. Residual stresses are found to be caused by temperature dependent moduli and CTE mismatches. Cure conditions are found to have an influence on adhesive strength. Finally, a bondability diagram is found to be effective in summarizing cure studies.

A series of pi-electron-rich macrocyclic polyethers incorporating the dioxybenzene (hydroquinone) and/or dioxynaphthalene units were synthesized in good yields by simple two-step processes. These macrocycles can bind bipyridinium-based guests due to a series of cooperative noncovalent bonding interactions. The efficiencies of these self-assembly procedures were observed to depend on the stereoelectronic characteristics of the pi-electron-rich macrocycles.

My purpose here is to provide brief historical overviews of three related subjects conceptually fundamental to the broader subject of 'cell adhesion in development.' These subjects are (1) the evolution of our present understanding of how animal cells cohere; (2) the question of what principles underlie the ability of embryonic cell populations to organize themselves into anatomically correct structures; and (3) the ongoing effort to understand the origins of the 'recognition specificity' evinced in the latter phenomenon. Because this review must be brief, it is not possible to mention all of the significant advances, many of which will be referenced in a recent more detailed review of this subject (Grunwald, 1991). For the same reason, the important work on cell adhesion in nonvertebrate systems is not included.