Science

Search by keywords:
Total Articles 64 - 72 of 6039 | |

Acknowledgement to Reviewers of Diversity in 2013

Author(s):Diversity Editorial Office
Journal: Diversity
Publisher:
Abstract
| Pages: 176-177
The editors of Diversity would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2013. [...]  

Meta-Analysis of Mitochondrial DNA Reveals Several Population Bottlenecks during Worldwide Migrations of Cattle

Author(s):Johannes A. Lenstra, Paolo Ajmone-Marsan, Albano Beja-Pereira, Ruth Bollongino, Daniel G. Bradley, Licia Colli, Anna De Gaetano, Ceiridwen J. Edwards, Marleen Felius, Luca Ferretti, Catarina Ginja, 
Journal: Diversity
Publisher:
Abstract
| Pages: 178-187
Several studies have investigated the differentiation of mitochondrial DNA in Eurasian, African and American cattle as well as archaeological bovine material. A global survey of these studies shows that haplogroup distributions are more stable in time than in space. All major migrations of cattle have shifted the haplogroup distributions considerably with a reduction of the number of haplogroups and/or an expansion of haplotypes that are rare or absent in the ancestral populations. The most extreme case is the almost exclusive colonization of Africa by the T1 haplogroup, which is rare in Southwest Asian cattle. In contrast, ancient samples invariably show continuity with present-day cattle from the same location. These findings indicate strong maternal founder effects followed by limited maternal gene flow when new territories are colonized. However, effects of adaptation to new environments may also play a role.

Advances on Optical Fiber Sensors

Author(s):Luciano Mescia -- Francesco Prudenzano
Journal: Fibers
Publisher:
Abstract
| Pages: 1-23
In this review paper some recent advances on optical fiber sensors are reported. In particular, fiber Bragg grating (FBG), long period gratings (LPGs), evanescent field and hollow core optical fiber sensors are mentioned. Examples of recent optical fiber sensors for the measurement of strain, temperature, displacement, air flow, pressure, liquid-level, magnetic field, and the determination of methadone, hydrocarbons, ethanol, and sucrose are briefly described.

Energy Transfer between Er3+ and Pr3+ for 2.7 μm Fiber Laser Material

Author(s):Xiangtan Li -- Binhua Yang -- Junjie Zhang -- Lili Hu -- Liyan Zhang
Journal: Fibers
Publisher:
Abstract
| Pages: 24-33
Energy transfer mechanisms between Er3+ and Pr3+ in Er3+/Pr3+ codoped germinate glass are investigated in detail. Under 980 nm LD pumping, 2.7 μm fluorescence intensity enhanced greatly. Meanwhile, 1.5 μm lifetime and fluorescence were suppressed deeply due to the efficient energy transfer from Er3+:4I13/2 to Pr3+:3F3,4, which depopulates the 4I13/2 level and promotes the 2.7 μm transition effectively. The obvious change in J-O parameters indicates that Pr3+ influences the local environment of Er3+ significantly. The increased spontaneous radiative probability in Er3+/Pr3+ glass is further evidence for enhanced 4I11/2 → 4I13/2 transition. The Er3+:4I11/2→Pr3+:1G4 process is harmful to the population accumulation on 4I11/2 level, which inhibits the 2.7 μm emission. The microscopic energy transfer coefficient of Er3+:4I13/2→Pr3+:3F3,4is 42.25 × 10−40 cm6/s, which is 11.5 times larger than that of Er3+:4I11/2→Pr3+:1G4. Both processes prefer to be non-phonon assisted, which is the main reason why Pr3+ is so efficient in Er3+:2.7 μm emission.

Hierarchically Self-Assembled Nanofiber Films from Amylose-Grafted Carboxymethyl Cellulose

Author(s):Daisuke Hatanaka -- Yasutaka Takemoto -- Kazuya Yamamoto -- Jun-ichi Kadokawa
Journal: Fibers
Publisher:
Abstract
| Pages: 34-44
In this paper, we report the formation of hierarchically self-assembled nanofiber films from amylose-grafted sodium carboxymethyl celluloses (NaCMCs) that were synthesized by a chemoenzymatic approach. First, maltooligosaccharide primer-grafted NaCMCs were prepared by a chemical reaction using two kinds of NaCMCs with different degrees of polymerization (DPs) from Avicel and cotton sources. Then, phosphorylase-catalyzed enzymatic polymerization of α-d-glucose 1-phosphate from the nonreducing ends of the primer chains on the products was conducted to produce the prescribed amylose-grafted NaCMCs. The films were obtained by drying aqueous alkaline solutions of the amylose-grafted NaCMCs. The scanning electron microscopy (SEM) image of the film fabricated from the material with the higher DP from the cotton source showed a clear, self-assembled, highly condensed tangle of nanofibers. The SEM image of the material with the lower DP from the Avicel source, on the other hand, showed an unclear nanofiber morphology. These results indicate that the DPs of the main chains in the materials strongly affected the hierarchically self-assembled nanofiber formation. The SEM images of the films after washing out the alkali, furthermore, showed that the fibers partially merged with each other at the interfacial area owing to the double helix formation between the amylose-grafted chains. The mechanical properties of the films under tensile mode also depended on the self-assembled morphologies of the amylose-grafted NaCMCs from the different sources.

The Significance and Insignificance of Carbon Nanotube-Induced Inflammation

Author(s):Matthew S.P. Boyles -- Linda C. Stoehr -- Paul Schlinkert -- Martin Himly -- Albert Duschl
Journal: Fibers
Publisher:
Abstract
| Pages: 45-74
In the present review article immune responses induced by carbon nanotubes (CNTs) are addressed. As inhalation is considered to be the primary entry route, and concern has been raised by similar high aspect ratio materials, the main focus lies on immune responses upon pulmonary exposure. Inflammation-related findings from both in vivo studies and in vitro models are reviewed, and the major responsible characteristics, which may drive CNT-induced inflammation in the lung, are discussed. In a second part, responses upon intentional administration of CNTs via subcutaneous and intravenous application are addressed, including their potential benefits and drawbacks for immunotherapy. Finally, the gastrointestinal tract as an alternative exposure route is briefly discussed. While there are many studies identifying numerous other factors involved in CNT-driven toxicity, e.g., cytotoxicity, oxidative stress, and genotoxicity, the focus of this review was kept solely on CNT-induced inflammation. Overall the literature has shown that CNTs are able to induce inflammation, which in some cases was a particularly robust response coinciding with the development of pro-fibrotic conditions. In the majority of cases the greatest inflammatory responses were associated with CNTs of considerable length and a high aspect ratio, accompanied by other factors like dispersion and sample purity.

Multi-Functional Magnetic Photoluminescent Photocatalytic Polystyrene-Based Micro- and Nano-Fibers Obtained by Electrospinning

Author(s):Michel Schaer -- Mireille Crittin -- Lamia Kasmi -- Katarzyna Pierzchala -- Caroline Calderone -- Reinaldo G. Digigow -- Alke Fink -- László Forró -- Andrzej Sienkiewicz
Journal: Fibers
Publisher:
Abstract
| Pages: 75-91
This work reports on the implementation of electrospinning (ES) as a facile route to encapsulate nano-engineered materials in a polystyrene (PS) matrix. We applied ES to co-encapsulate two kinds of nanoparticles, i.e., upconversion nanophosphors (UCNPs) and superparamagnetic iron oxide nanoparticles (SPIONs), in polystyrene (PS)-based micro- and nano-fibers (PSFs). This approach made it possible to integrate near-infrared (NIR) light-sensitive 500-nm β-NaYF4:Yb, Er UCNPs with 10-nm γ-Fe2O3 SPIONs in PS fibers. During the ES process, PSFs were additionally loaded with a well-established singlet oxygen (1∆g) photosensitizer, rose bengal (RB). The thus obtained PSFs revealed the promising features of prospective multi-functional magnetic photoluminescent photocatalytic nano-constructs.

Reliable Lifetime Prediction for Passivated Fiber Bragg Gratings for Telecommunication Applications

Author(s):Matthieu Lancry -- Bertrand Poumellec -- Sylvain Costes -- Julien Magné
Journal: Fibers
Publisher:
Abstract
| Pages: 92-107
This paper is dedicated to the lifetime prediction of Type I Fiber Bragg gratings (FBG) and to problems that happen when stabilization (also called passivation) conditions or the industrial conditioning procedure depart from ageing ones (e.g., presence of hydrogen during the passivation process). For the first time, a reliable procedure to certify the predicted lifetime based on a “restricted” master curve built on real components (i.e., passivated FBG) is presented. It is worth noting that both procedures (master curve built on non-passivated or on passivated components) are based on the same model (demarcation energy approximation and the existence of a master curve) fed with ageing data (reflectivity decay vs. time and temperature). If the Master Curve (MC) build on passivated components can be derived from the original one, we can certify the lifetime prediction in a reliable manner.

Release of Carbon Nanotubes from Polymer Nanocomposites

Author(s):Lukas Schlagenhauf -- Frank Nüesch -- Jing Wang
Journal: Fibers
Publisher:
Abstract
| Pages: 108-127
Carbon nanotube (CNT)/polymer nanocomposites have superior properties compared to the neat polymer matrix. They now are widely used in industry, but questions have been raised about the risks of such materials since CNTs can be toxic when inhaled. For a risk assessment of CNT nanocomposites, it is crucial to know whether CNTs from nanocomposites can be released into the environment or if they remain embedded in the matrix. This review article summarizes the studies that investigated the release of CNTs from nanocomposites during the service life. Three scenarios are reviewed, the release of particles due to mechanical impact, the release due to weathering processes, and the release due to fire. A release during composite production and disposal is not incorporated.
Page:12345678910Next