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At least 739 records · Page 41Linked to original sources
PubMed2000

Femtosecond self-guided atmospheric light strings.

The onset and recurrence of multiple filamentary structures in the long-distance propagation of high power femtosecond laser pulses in air displays features analogous to strong turbulence events observed in many areas of physics. However, dissipation is not a key player in regularizing the underlying singular dynamical events. The collapse singularity of the two-dimensional (2D) nonlinear Schrodinger equation is identified as the robust nonlinear mode which both initiates and sustains the waveguide. Physical collapse regularization mechanisms include normal group velocity dispersion and plasma generation in the high intensity nonlinear focal regions. Plasma absorption is weak and the dominant process is the transient generation of a highly localized strongly defocusing lens which evacuates the light behind the leading intense light filament. Consequently the nonlinear waveguide formed is highly dynamic. (c) 2000 American Institute of Physics.

Journal Article↗
PubMed2001

Tuning DNA "strings": modulating the rate of DNA replication with mechanical tension.

Recent experiments have measured the rate of replication of DNA catalyzed by a single enzyme moving along a stretched template strand. The dependence on tension was interpreted as evidence that T7 and related DNA polymerases convert two (n = 2) or more single-stranded template bases to double helix geometry in the polymerization site during each catalytic cycle. However, we find structural data on the T7 enzyme--template complex indicate n = 1. We also present a model for the "tuning" of replication rate by mechanical tension. This model considers only local interactions in the neighborhood of the enzyme, unlike previous models that use stretching curves for the entire polymer chain. Our results, with n = 1, reconcile force-dependent replication rate studies with structural data on DNA polymerase complexes.

Bacteriophage T7↗
PubMed1997

Protective anti-tumor immunity induced by vaccination with recombinant adenoviruses encoding multiple tumor-associated cytotoxic T lymphocyte epitopes in a string-of-beads fashion.

Vaccines harboring genes that encode functional oncoproteins are intrinsically hazardous, as their application may lead to introduction of these genes into normal cells and thereby to tumorigenesis. On the other hand, oncoproteins are especially attractive targets for immunotherapy of cancer, as their expression is generally required for tumor growth, making the arisal of tumor variants lacking these antigens unlikely. Using murine tumor models, we investigated the efficacy of polyepitope recombinant adenovirus (rAd) vaccines, which encode only the immunogenic T cell epitopes derived from several oncogenes, for the induction of protective anti-tumor immunity. We chose to employ rAd, as these are safe vectors that do not induce the side effects associated with, for example, vaccinia virus vaccines. A single polyepitope rAd was shown to give rise to presentation of both H-2 and human leukocyte antigen-restricted cytotoxic T lymphocyte (CTL) epitopes. Moreover, vaccination with a rAd encoding H-2-restricted CTL epitopes, derived from human adenovirus type 5 early region 1 and human papilloma virus type 16-induced tumors, elicited strong tumor-reactive CTL and protected the vaccinated animals against an otherwise lethal challenge with either of these tumors. The protection induced was superior compared with that obtained by vaccination with irradiated tumor cells. Thus, vaccination with polyepitope rAd is a powerful approach for the induction of protective anti-tumor immunity that allows simultaneous immunization against multiple tumor-associated T cell epitopes, restricted by various major histocompatibility complex haplotypes.

Adenoviridae↗
PubMed1998

String theory.

Explore the source record for details and available documents.

Elementary Particles↗
PubMed2001

Improved DNA binding specificity from polyzinc finger peptides by using strings of two-finger units.

Multizinc finger peptides are likely to reach increased prominence in the search for the "ideal" designer transcription factor for in vivo applications such as gene therapy. However, for these treatments to be effective and safe, the peptides must bind with high affinity and, more importantly, with great specificity. Our previous research has shown that zinc finger arrays can be made to bind 18 bp of DNA with picomolar affinity, but also has suggested that arrays of fingers also may bind tightly to related sequences. This work addresses the question of zinc finger DNA binding specificity. We show that by changing the way in which zinc finger arrays are constructed--by linking three two-finger domains rather than two three-finger units--far greater target specificity can be achieved through increased discrimination against mutated or closely related sequences. These new peptides have the added capability of being able to span two short gaps of unbound DNA, although still binding with picomolar affinity to their target sites. We believe that this new method of constructing zinc finger arrays will offer greater efficacy in the fields of gene therapy and in the production of transgenic organisms than previously reported zinc finger arrays.

Animals↗
PubMed1995

A string of enzymes, purification and characterization of a fusion protein comprising the four subunits of the glucose phosphotransferase system of Escherichia coli.

A multidomain protein comprising the four subunits of the glucose phosphotransferase system of Escherichia coli was constructed by fusion of the transmembrane subunit IICBGlc and the three cytoplasmic proteins, IIAGlc, HPr, and enzyme I. The subunits were linked in the above order with Ala-Pro-rich linkers; the fusion protein was overexpressed in E. coli and purified by Ni2+ chelate affinity chromatography. Approximately 3 mg of the fusion protein could be purified from 1 liter of culture. The phosphotransferase activity of the purified fusion protein was 3-4 times higher than that of an equimolar mixture of the isolated subunits. The mannose transporter, which also requires enzyme I and HPr, was not an effective competitor in the overall phosphoryltransfer reaction when the fusion protein was used, whereas it was a competitor when an equimolar mixture of the separate subunits was employed. Transphosphorylation activity of the fusion protein was almost indistinguishable from the wild-type IICBglc. Addition of extra IICBGlc subunit could significantly stimulate the phosphotransferase activity of the fusion protein, addition of extra IIAGlc subunit and enzyme I, in contrast, was slightly inhibitory, and HPr had almost no effect. An optimal detergent-lipid ratio is required for maximum activity of the fusion protein. Our results suggest that Ala-Pro-rich linker sequences may be of general use for the construction of catalytically active fusion proteins with novel properties.

Amino Acid Sequence↗
PubMed1995

A new string to our bow: the role of a self-evaluation approach for drug and alcohol services.

In Australia there is a wide range and diversity of services and programmes to address the problems associated with the use of alcohol and other drugs. As with many other spheres of social welfare, the effectiveness of individual programmes in addressing these problems remains largely unexamined. In response to the absence of evaluation activity at this level of service provision one state health body, the New South Wales Drug and Alcohol Directorate, has developed a project to promote programme evaluation for agencies providing drug and alcohol services in their jurisdictions. This paper provides a description of the project which involved the development of a "self-evaluation" method based on the comparison of programme objectives and actual outcomes. The implementation of this method involved the use of a resource kit, workshops conducted in each health area and region in New South Wales and individual consultation with service providers and drug and alcohol co-ordinators. The preliminary results of an evaluation of the project itself are also described. Evaluation activity has commenced in almost half the services participating in the workshops and participants reported a significant increase in knowledge and skills in evaluation. They also reported a decrease in anxiety about evaluation as a result of the workshops. The paper concludes by placing the project in the broader context of state and national strategic planning.

Journal Article↗
PubMed2006

Explicit-VR transfer syntax limits the value multiplicity of DICOM data elements with decimal string (DS) value representation.

The Advanced Technology QA Consortium (ATC) has identified a problem in the encoding of DICOM RT Dose objects when these objects are converted from Implicit-VR (Little-Endian) transfer syntax to an Explicit-VR transfer syntax. There exist data elements, which can be represented in Implicit-VR Little-Endian transfer syntax but that cannot be represented in Explicit-VR Little-Endian transfer syntax.

Clinical Trials as Topic↗
PubMed1998

STRIRED: graphical analysis of string repeats.

UNLABELLED: STRIRED is a toolkit to generate a graphical picture of the distribution of 4- to 6-mer repeats in a set of user-defined nucleic acid sequences. AVAILABILITY: The STRIRED package can be downloaded as self-extracting archive (strired.exe) by anonymous FTP from biol.dgbm.unina.it (143.225.252.1), in the directory /software/win95/STRIRED. CONTACT: calogero@biol.dgbm.unina. it.

Base Sequence↗
PubMed2003

STRING: finding tandem repeats in DNA sequences.

MOTIVATION AND RESULTS: The importance of Tandem Repeats in some genomes is now well established. We have reported elsewhere some interesting new results obtained by means of a preliminary program for finding Tandem Repeats in DNA sequences, together with a brief description of the basic ideas of the algorithm. We describe here a completely new program based only in part on those ideas, we briefly discuss the interpretation of the results, and, by way of example, we provide a few novel results relative to the parasites responsible of two re-emerging diseases, Plasmodium falciparum and Mycobacterium tuberculosis. Our program is portable, effective, powerful and fast: it can run on current desktop computers, and it finds all significant Tandem Repeats also in the longest segments of sequences in databases (up to millions of bases), in short times (minutes). AVAILABILITY: An academic version of the algorithm (full source listing in standard C language) can be freely downloaded (http://www.caspur.it/~castri/STRING/). SUPPLEMENTARY INFORMATION: Some illustrative figures and some sample results are provided as supplementary material at: http://www.caspur.it/~castri/STRING/

Algorithms↗