Mechanics of biological networks: from the cell cytoskeleton to connective tissue.

From the cell cytoskeleton to connective tissues, fibrous networks are ubiquitous in metazoan life as the key promoters of mechanical strength, support and integrity. In recent decades, the application of physics to biological systems has made substantial strides in elucidating the striking mechanical phenomena observed in such networks, explaining strain stiffening, power law rheology and cytoskeletal fluidisation - all key to the biological function of individual cells and tissues. In this review we focus on the current progress in the field, with a primer into the basic physics of individual filaments and the networks they form. This is followed by a discussion of biological networks in the context of a broad spread of recent in vitro and in vivo experiments.

Intelectin gene from the grass carp Ctenopharyngodon idella: cDNA cloning, tissue expression, and immunohistochemical localization

The cDNA encoding grass carp intelectin was isolated from a head kidney cDNA library, and termed gcIntL. The deduced amino acid sequence of gcIntL consists of 318 amino acids, and about 55% identical and 74% similar to human intelectin, which is a new type of lectin recognizing galactofuranose, and plays a role in the recognition of bacteria-specific components in animal hosts. The gcIntL gene consists of seven exons and six introns, spacing over approximately 3 kb of genomic sequence. Phylogenetic analysis clearly demonstrated that the gcIntL formed a clade with Danio rerio intelectin and 35 kDa serum lectin. By real-time quantitative RT-PCR analysis, gcIntL transcripts were significantly induced in head kidney, trunk kidney, spleen, and intestine from LPS-stimulated fish. RT-PCR and Western blotting analysis demonstrated that the mRNA and protein of gcIntL gene have the same expression pattern, and both were detected in brain, gill, intestine, head kidney, trunk kidney, spleen, and heart. Furthermore, gcIntL protein could be detected in gill, intestine, trunk kidney, head kidney, spleen, heart, and brain including medulla oblongata and optic lobe, as determined by immunohistochemistry. This is the first report of intelectin expression pattern in fish, and of recombinant gcIntL and polyclonal antibody against gcIntL. (c) 2006 Elsevier Ltd. All rights reserved.

The forming of variable cross-section I-beams by hot rolling

A process is presented for the forming of variable cross-section I-beams by hot rolling. Optimized I-beams with variable cross-section offer a significant weight advantage over prismatic beams. By tailoring the cross-section to the bending moment experienced within the beam, around 30% of the material can be saved compared to a standard section. Production of such beams by hot rolling would be advantageous, as It combines high volume capacity with high material yields. Through controlled variation of the roll gap during multiple passes, beams with a variable cross-section have been created using shaped rolls similar to those used for conventional I-beam rolling. The process was tested experimentally on a small scale rolling mill, using plasticine as the modelling material. These results were then compared to finite element simulations of individual stages of the process conducted using Abaqus/Standard. Results here show that the process can successfully form a beam with a variable depth web. The main failure modes of the process, and the limitations on the achievable variations In geometry are also presented. Finally, the question of whether or not optimal beam geometries can be created by this process Is discussed. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.

270GHz, 580fs Optical Pulse Generation from a single-section quantum-dash fabry-pérot laser using frequency multiplication

Pulse generation from a mode-locked single-section 1.55μm quantum-dash FP laser is demonstrated under continuous-wave operation. A 270GHz, 580fs pulse train is achieved by applying frequency multiplication using fiber dispersion. ©2009 Optical Society of America.

Tissue distributions and seasonal dynamics of the hepatotoxic microcystins-LR and -RR in two freshwater shrimps, Palaemon modestus and Macrobrachium nipponensis, from a large shallow, eutrophic lake of the subtropical China

So far no information is available on microcystin (MC) contents in shrimps, prawns or crayfish from natural freshwaters. Tissue distributions and seasonal dynamics of the hepatotoxic MC-LR and -RR in two freshwater shrimps, Palaemon modestus and Macrobrachium nipponensis were studied monthly (during June-November, 2003) in a Chinese lake containing toxic cyanobacterial blooms. The shrimps P. modestus and M. nipponensis accumulated high MCs not only in the hepatopancreas (mean 4.29 and 0.53 mu g g(-1) DW, respectively) but also in the gonad (mean 1.17 and 0.48 mu g g-1 DW, respectively), and the crayfish Procambarus clarkii accumulated as much as 0.93 mu g g(-1) DW in the gonad. This indicates that gonads of these invertebrates are the second important target organ of MCs. P. modestus apparently accumulated more MCs in their organs than M. nipponensis, which might be a reflection of their difference in trophic niche. Eggs of the shrimps accumulated 8.4% (M. nipponensis, 0.27 mu g g(-1) DW) and 29.0% (P. modestus, 2.34 mu g g(-1) DW) of total toxin burden, indicating that MCs had been transferred into offspring from their adults. Among the shrimp muscle samples analyzed, 31% were above the provisional WHO TDI level, suggesting the risk of consuming shrimps in Lake Chaohu. (c) 2005 Elsevier Ltd. All rights reserved.

Tissue distributions and seasonal dynamics of the hepatotoxic microcystins-LR and -RR in a freshwater snail (Bellamya aeruginosa) from a large shallow, eutrophic lake of the subtropical China

Tissue distributions and seasonal dynamics of the hepatotoxic microcystins-LR and -RR in a freshwater snail (Bellamya aeruginosa) were studied monthly in a large shallow, eutrophic lake of the subtropical China during June-November, 2003. Microcystins (MCs) were quantitatively determined by High-Performance Liquid Chromatography (HPLC) with a qualitative analysis by a Finnigan LC-MS system. On the average of the study period, hepatopancreas was the highest in MC contents (mean 4.14 and range 1.06-7.42 mug g(-1) DW), followed by digestive tracts (mean 1.69 and range 0.8-4.54 mug g(-1) DW) and gonad (mean 0.715 and range 0-2.62 mug g(-1) DW), whereas foot was the least (mean 0.01 and range 0-0.06 mug g(-1) DW). There was a positive correlation in MC contents between digestive tracts and hepatopancreas. A constantly higher MC content in hepatopancreas than in digestive tracts indicates a substantial bioaccumulation of MCs in the hepatopancreas of the snail. The average ratio of MC-LR/MC-RR showed a steady increase from digestive tracts (0.44) to hepatopancreas (0.63) and to gonad (0.96), suggesting that MC-LR was more resistant to degradation in the snail. Since most MCs were present in the hepatopancreas, digestive tracts and gonad with only a very small amount in the edible foot, the risk to human health may not be significant if these toxic parts are removed prior to snail consumption. However, the possible transference of toxins along food chains should not be a negligible concern. (C) 2004 Elsevier Ltd. All rights reserved.

Relationship between tissue concentrations of polycyclic aromatic hydrocarbons and DNA adducts in green-lipped mussels (Perna viridis)

Green-lipped mussels (Perna viridis) were collected from a site in Hong Kong which is relatively free from polycyclic aromatic hydrocarbon (PAH) contamination, and maintained in situ at this and three other sites with different degrees of PAH contamination. The transplanted mussels were retrieved after a 30-day field exposure. DNA adducts in the gill tissues were quantified, and tissue concentrations of benzo[a]pyrene as well as total PAHs (with potential carcinogenicity) determined for individual mussels. Results indicate that (1) tissue concentration of PAHs and adduct levels in mussels collected from a single site can be highly variable; and (2) adduct levels were related to tissue concentrations of benzo[a]pyrene as well as total PAHs of individual animals.

Self-pulsation in a two-section DFB laser with a varied ridge width

A 1.55 mu m InGaAsP-InP two-section DFB laser with a variable ridge width has been fabricated. Self-pulsations with frequencies around 3 GHz and 40 GHz are observed. The pulsation mechanisms related to the two frequencies are discussed and the tunability of generated self-pulsations is studied.

A ridge width varied two-section index-coupled DFB self-pulsation laser with a wide continuously tunable frequency range

A 1.55 mu m InGaAsP-InP index-coupled two-section DFB self-pulsation laser (SPL) with a varied ridge width has been fabricated. A record wide self-pulsation tuning range above 450 GHz has been achieved for this index-coupled DFB SPL. Furthermore, frequency locking to an optically injected modulated signal is successfully demonstrated.

Single-mode condition for silicon rib waveguides with trapezoidal cross-section

Single-mode condition for silicon rib waveguides with trapezoidal cross-section was obtained using a numerical method based on imaginary-distance beam propagation method with non-uniform discretization. Both quasi-transverse-electric and quasi-transverse-magnetic modes were investigated. Simulated single-mode condition is given by a modified equation. Comparison with reported results shows that the Marcatili's method is in a better agreement with our results. (C) 2003 Elsevier B.V. All rights reserved.

Multimode interference 3-dB coupler in silicon-on-insulator based on silicon rib waveguides with trapezoidal cross section

A 3-dB multimode interference optical coupler based on rib waveguides with trapezoidal cross section was designed and fabricated on silicon-on-insulator wafer. Potassium hydroxide (KOH) anisotropic chemical etching of silicon was used to fabricate the waveguides to obtain smooth interface. A modified finite-difference beam propagation method was used to simulate the multimode rib waveguide with slope interfaces. The rms roughness of etching interface is as small as 1.49 nm. The propagation loss of the waveguide is 1.3 dB/cm at wavelength of 1.55 mum. The fabricated 3-dB coupler has a good uniformity of 0.2 dB.

Fabrication of 4 x 4 tapered MMI coupler with large cross section

MMI coupler with large cross section has low coupling loss between the device and fiber. However, large chip area is required. Recently proposed N x N tapered MMI coupler shows a substantial reduction in device geometry. No such kind of devices with N > 2 has yet been realized up to now. The authors have demonstrated a 4 x 4 parabolically tapered MMI coupler with large cross section that can match the SM fiber in silicon-on-insulator (SOI) technology. The device exhibits a minimum uniformity of 0.36 dB and excess loss of 3.7 dB, It represents a key component for realization of MMI-based silicon integrated optical circuit technology.

All-optical clock recovery using a ridge width varied two-section partly gain-coupled DFB self-pulsation laser

A 1.55 mu m InGaAsP-InP partly gain-coupled two-section DFB self-pulsation laser (SPL) with a varied ridge width has been fabricated. The laser produces self-pulsations with a frequency tuning range of more than 135 GHz. All-optical clock recovery from 40 Gb/s degraded data streams has been demonstrated. Successful lockings of the device at frequencies of 30 GHz, 40 GHz, 50 GHz, and 60 GHz to a 10 GHz sidemode injection are also conducted, which demonstrates the capability of the device for all-optical clock recovery at different frequencies. This flexibility of the device is highly desired for practical uses. Crown Copyright