Mixed alkanethiol monolayers on submicrometric gold patterns: a controlled platform for studying cell-ligand interactions

Nanoscale organization of surface ligands often has a critical effect on cell-surface interactions. We have developed an experimental system that allows a high degree of control over the 2-D spatial distribution of ligands. As a proof of concept, we used the developed system to study how T-cell activation is independently affected by antigen density and antigen amount per cell. Arrays of submicrometer gold islands at varying surface coverage were defined on silicon by electron beam lithography (EBL). The gold islands were functionalized with alkanethiol self-assembled monolayers (SAMs) containing a small antigen, 2,4,6-trinotrophenyl (TNP), at various densities. Genetically engineered T-cell hybridomas expressing TNP-specific chimeric T-cell antigen receptor (CAR) were cultured on the SAMs, and their activation was assessed by IL-2 secretion and CD69 expression. It was found that, at constant antigen density, activation increased monotonically with the amount of antigen, while at constant antigen amount activation was maximal at an intermediate antigen density, whose value was independent of the amount of antigen.     

Generation of fast protons by interaction of modest laser intensities with H2O “snow” nano-wire targets

We report on the generation of protons with energies of 5.5 MeV when irradiating an H₂O nano-wire layer grown on a sapphire plate with an intensity of 5×10¹⁷ W/cm². A theoretical model is suggested in which plasma near the tip of the wire is subject to enhanced electrical fields and protons are accelerated to several MeVs.     

Emerging Scanning Probe–Based Setups for Advanced Nanoelectronic Research

Scanning probe microscopy (SPM) refers to a family of techniques that have become essential to study many different properties of materials and devices at the nanoscale. All of them have in common that they use an ultrasharp probe tip to scan the surface of a sample. However, although many of these techniques are interrelated, some of them have become very sophisticated and require specific and deep study. While there are plenty of review articles available for most of these techniques, newer developments need to be carefully analyzed in a critical manner in order to promote their development. In this progress report, some of the newest SPM‐based developments that are expected to generate a larger impact in the field of nanoelectronics are discussed, and critical advice on how to improve each of them is provided. In particular, the combination of wear and electrical tests; scanning gate microscopy; the integration of conductive atomic force microscopy into scanning electron microscopy; and the integration of a scanning probe into transmission electron microscopy, multiprobe scanning tunneling microscopy, multiprobe atomic force microscopy, and fountain‐pen nanolithography are focused on.     

Transport phenomena in the human nasal cavity: a computational model

Development and growth of V1 begins during embryogenesis and continues postnatally. The growth of V1 has direct implications on the organization of features such as the retinotopic map and the pattern of visual cortical columns. We have examined the postnatal growth and two-dimensional shape of V1 in macaque monkeys, cats, and rats. The perimeter, area, and anterior-posterior length of V1 were measured from unfolded and flattened sections from neonatal and adult animals from each of these species. Although there were substantial differences in the overall amount of postnatal growth, from 18% in macaque monkeys to more than 100% in cats, in all three species the shape of V1 did not change during development. Thus, growth of the mammalian visual cortex is well described as an isotropic expansion, so the layout of the global features, such as the arrangement of ocular dominance columns and the retinotopic map, does not need to change during development. Furthermore, quantification of the shape confirms the observations that there is a similar, egg-like oval shape to the visual cortex of these mammalian species.     

Mapping Diversities and Tracing Trends of Cultural Homogeneity/Heterogeneity in Cyberspace

Many Internet global commercial services were originally initiated in the United States and later exported to other countries, continents, and cultures. By analyzing content and form characteristics of two leading portal sites—MSN and Yahoo!—on 33 and 23 (respectively) of their local country homepages in a comparative and longitudinal study over a period of six months, this study addresses two research questions: What differences, if any, are found among homepages of the same parent site located in different cultures (or targeted at audiences in different cultures)? What trends, if any, do those differences show over time? Although MSN is a U.S. brand, the analysis of its homepages reveals increasing cultural heterogeneity and localization of content and form. In contrast, Yahoo!’s homepages are found to be more similar to each other and to the “parent” American portal. A metric was developed to measure the distance between various websites in terms of form and content, along with a structured procedure to analyze and cluster groups of websites. The results suggest that the diversity of local homepages in MSN and Yahoo! follows the geographic and ethnographic scatter of their countries.     

The Hansenula polymorpha PDD1 gene product,essential for the selective degradation of peroxisomes,is a homologue of Saccharomyces cerevisiae Vps34p

Via functional complementation we have isolated the Hansenula polymorpha PDD1 gene essential for selective, macroautophagic peroxisome degradation. HpPDD1 encodes a 116 kDa protein with high similarity (42% identity) to Saccharomyces cerevisiae Vps34p, which has been implicated in vacuolar protein sorting and endocytosis. Western blotting experiments revealed that HpPDD1 is expressed constitutively. In a H. polymorpha pdd1 disruption strain peroxisome degradation is fully impaired. Sequestered peroxisomes, typical for the first stage of peroxisome degradation in H. polymorpha, were never observed, suggesting that HpPdd1p plays a role in the tagging of redundant peroxisomes and/or sequestration of these organelles from the cytosol. Possibly, HpPdd1p is the functional homologue of ScVps34p, because—like S. cerevisiae vps34 mutants—H. polymorpha pdd1 mutants are temperature‐sensitive for growth and are impaired in the sorting of vacuolar carboxypeptidase Y. Moreover, HpPdd1p is associated to membranes, as was also observed for ScVps34p. Copyright © 1999 John Wiley & Sons, Ltd.