Fabry - Perot interference in a nanotube electron waveguide

The behaviour of traditional electronic devices can be understood in terms of the classical diffusive motion of electrons. As the size of a device becomes comparable to the electron coherence length, however, quantum interference between electron waves becomes increasingly important, leading to dramatic changes in device properties. This classical-to-quantum transition in device behaviour suggests the possibility for nanometer-sized electronic elements that make use of quantum coherence. Molecular electronic devices are promising candidates for realizing such device elements because the electronic motion in molecules is inherently quantum mechanical and it can be modified by well defined chemistry. Here we describe an example of a coherent molecular electronic device whose behaviour is explicitly dependent on quantum interference between propagating electron waves-a Fabry-Perot electron resonator based on individual single-walled carbon nanotubes with near-perfect ohmic contacts to electrodes. In these devices, the nanotubes act as coherent electron waveguides, with the resonant cavity formed between the two nanotube-electrode interfaces. We use a theoretical model based on the multichannel Landauer-Büttiker formalism to analyse the device characteristics and find that coupling between the two propagating modes of the nanotubes caused by electron scattering at the nanotube-electrode interfaces is important.     

Molecular mechanism for duplication 17p11.2- the homologous recombination reciprocal of the Smith-Magenis microdeletion

Recombination between repeated sequences at various loci of the human genome are known to give rise to DNA rearrangements associated with many genetic disorders. Perhaps the most extensively characterized genomic region prone to rearrangement is 17p12, which is associated with the peripheral neuropathies, hereditary neuropathy with liability to pressure palsies (HNPP) and Charcot-Marie-Tooth disease type 1A (CMT1A;ref. 2). Homologous recombination between 24-kb flanking repeats, termed CMT1A-REPs, results in a 1.5-Mb deletion that is associated with HNPP, and the reciprocal duplication product is associated with CMT1A (ref. 2). Smith-Magenis syndrome (SMS) is a multiple congenital anomalies, mental retardation syndrome associated with a chromosome 17 microdeletion, del(17)(p11.2p11.2) (ref. 3,4). Most patients (>90%) carry deletions of the same genetic markers and define a common deletion. We report seven unrelated patients with de novo duplications of the same region deleted in SMS. A unique junction fragment, of the same apparent size, was identified in each patient by pulsed field gel electrophoresis (PFGE). Further molecular analyses suggest that the de novo17p11.2 duplication is preferentially paternal in origin, arises from unequal crossing over due to homologous recombination between flanking repeat gene clusters and probably represents the reciprocal recombination product of the SMS deletion. The clinical phenotype resulting from duplication [dup(17)(p11.2p11.2)] is milder than that associated with deficiency of this genomic region. This mechanism of reciprocal deletion and duplication via homologous recombination may not only pertain to the 17p11.2 region, but may also be common to other regions of the genome where interstitial microdeletion syndromes have been defined.     

CD1-restricted T-cell responses and microbial infection

CD1, a conserved family of major histocompatibility (MHC)-like glycoproteins in mammals, specializes in capturing lipid rather than peptide antigen for presentation to T lymphocytes. The principles and mechanisms of this newly discovered immune strategy differ markedly from those governing classical MHC-peptide presentation. They might be exploited for the design of new lipid-based microbial vaccines and adjuvants.     

CD43, a molecule defective in Wiskott-Aldrich syndrome, binds ICAM-1.

THE protein CD43 (also known as sialophorin, leukosialin, large sialoglycoprotein or gp115) is expressed on the surface of T lymphocytes, monocytes, neutrophils, platelets and some B lymphocytes. Expression of CD43 is deficient and/or defective in the X-chromosome-linked immunodeficiency disorder Wiscott-Aldrich syndrome, suggesting that CD43 might have a role in T-cell activation. We have shown that expression of human CD43 in an HLA-DR-specific murine T-cell hybridoma enhances the antigen-specific response to stimulation by the human lymphoblastoid cell line Daudi, and that Daudi cells bind specifically to purified immobilized CD43. These data indicate that the specific interaction of CD43 with a ligand on the surface of Daudi cells might contribute to T-cell activation. Here we report evidence that intercellular adhesion molecule-1 (ICAM-1, or CD54), is a ligand for CD43.     

Chemotaxis of human neutrophils against gravity: A new method

Summary A new method is described in which human neutrophils were made to migrate upward and against gravity. Thus, the possible effect of gravity on cell migration and consequent detachment of cell after migration have been eliminated.Supported in part by N.I.H. grants: No.HL19628-03, No. DE04898, No. CA24215 and No.RR05493).     

Cellular responses to mild heat stress

Since its discovery in 1962 by Ritossa, the heat shock response has been extensively studied by a number of investigators to understand the molecular mechanism underlying the cellular response to heat stress. The most well characterized heat shock response is induction of the heat shock proteins that function as molecular chaperones and exert cell cycle regulatory and anti-apoptotic activities. While most investigators have focused their studies on the toxic effects of heat stress in organisms such as severe heat stress-induced cell cycle arrest and apoptosis, the cellular response to fever-ranged mild heat stress has been rather underestimated. However, the cellular response to mild heat stress is likely to be more important in a physiological sense than that to severe heat stress because the body temperature of homeothermic animals increases by only 1–2°C during febrile diseases. Here we provide information that mild heat stress does have some beneficial role in organisms via positively regulating cell proliferation and differentiation, and immune response in mammalian cells.Received 14 May 2004; received after revision 2 August 2004; accepted 16 August 2004     

Tuning clathrate hydrates for hydrogen storage

The storage of large quantities of hydrogen at safe pressures is a key factor in establishing a hydrogen-based economy. Previous strategies--where hydrogen has been bound chemically, adsorbed in materials with permanent void space or stored in hybrid materials that combine these elements--have problems arising from either technical considerations or materials cost. A recently reported clathrate hydrate of hydrogen exhibiting two different-sized cages does seem to meet the necessary storage requirements; however, the extreme pressures (approximately 2 kbar) required to produce the material make it impractical. The synthesis pressure can be decreased by filling the larger cavity with tetrahydrofuran (THF) to stabilize the material, but the potential storage capacity of the material is compromised with this approach. Here we report that hydrogen storage capacities in THF-containing binary-clathrate hydrates can be increased to approximately 4 wt% at modest pressures by tuning their composition to allow the hydrogen guests to enter both the larger and the smaller cages, while retaining low-pressure stability. The tuning mechanism is quite general and convenient, using water-soluble hydrate promoters and various small gaseous guests.     

IgM levels of newborn in Hawaii

Zusammenfassung Es wird eine Radial-Immun.-Diffusionsmethode verwendet, um durch Vergleich der IgM-Antikörper im Nabelschnurblut zu bestimmen, ob im den homologen mütterlichen Proben eine asymptotische Infektion stattgefunden hat. Es ergab sich, dass das benutzte Verfahren nicht zur Klärung der gestellten Frage geeignet ist.

---

---

This study was supported by a Kapiolani Maternity Hospital Research Grant and the Mrs. Lois A. Mayer Family Fund.

---

Acknowledgment. The authors indebted to Mrs.L. Hann, MT (ASCP) for her technical assistance and Mr.V. T. Oi for his critical review of this paper.