Ethernet-over-SONET(EoS) over WDM in Optical Wide-Area Networks (WANs): Benefits and Challenges

Ethernet has been playing an increasingly important role in wide area networks (WANs), from both a service perspective and a transport-technology perspective. Unlike its dominant presence in local area networks (LANs), Ethernet in WANs has been increasing its popularity in three different directions, i.e., Ethernet-based layer-2 virtual private network (L2VPN) over layer-3 network, Ethernet over SONET (EoS), and Ethernet directly over WDM channels or optical fibers. In this paper, we investigate the benefits and challenges of using next-generation SONET/SDH techniques—namely SONET/SDH virtual concatenation (VCAT) and link-capacity adjustment scheme (LCAS)—to support Ethernet-based data services in intelligent optical WDM wide area networks. In particular, we evaluate the network performance improvement after employing VCAT. In order to fully utilize VCATs inverse-multiplexing capability, several simple and effective heuristic algorithms are proposed and evaluated.*Part of the work was accomplished while Keyao Zhu was a Ph.D. student in the Networks Research Lab. at University of California, Davis, under the supervision of Professor Biswanath Mukherjee. Summarized versions of this paper were presented at the IEEE/OSA Optical Fiber Communication Conferences OFC03 and OFC04 in Atlanta, GA, in March 2003 and in Los Angeles, CA, in March 2004, respectively.Corresponding author     

Protein growth factors loaded highly porous chitosan scaffold: A comparison of bone healing properties

Present study aimed to investigate and compare effectiveness of porous chitosan alone and in combination with insulin like growth factor-1 (IGF-1) and bone morphogenetic protein-2 (BMP-2) in bone healing. Highly porous (85 ± 2%) with wide distribution of macroporous (70–900 μm) chitosan scaffolds were fabricated as bone substitutes by employing a simple liquid hardening method using 2% (w/v) chitosan suspension. IGF-1 and BMP-2 were infiltrated using vacuum infiltration with freeze drying method. Adsorption efficiency was found to be 87 ± 2 and 90 ± 2% for BMP-2 and IGF-1 respectively. After thorough material characterization (pore details, FTIR and SEM), samples were used for subsequent in vivo animal trial. Eighteen rabbit models were used to evaluate and compare control (chitosan) (group A), chitosan with IGF-1 (group B) and chitosan with BMP-2 (group C) in the repair of critical size bone defect in tibia. Radiologically, there was evidence of radiodensity in defect area from 60th day (initiated on 30th day) in groups B and C as compared to group A and attaining nearly bony density in most of the part at day 90. Histological results depicted well developed osteoblastic proliferation around haversian canal along with proliferating fibroblast, vascularization and reticular network which was more pronounced in group B followed by groups C and A. Fluorochrome labeling and SEM studies in all groups showed similar outcome. Hence, porous chitosan alone and in combination with growth factors (GFs) can be successfully used for bone defect healing with slight advantage of IGF-1 in chitosan samples.     

A novel bandwidth allocation scheme for OTSS-enabled flex-grid intra-datacenter networks

Photonic Network Communications - Optical circuit switching networks have been recognized as a promising solution for inter-datacenter networks. However, for intra-datacenter networks, they may...     

Structural and phase analysis of multi-ion doped hydroxyapatite for biomedical applications

Multi-ion doping in synthetic HA was carried out using high energy planetary ball milling followed by calcination at 1250?°C for 2?h. The influence of Sr⁺², Zn⁺², Ag⁺, and F^- ion doping on crystallinity and crystallite size was analyzed using Taguchi design of experiments (DOE) and optimal concentration of different dopants has been identified to achieve desired crystallinity and crystallite size. The doped HA samples have been characterized using X-ray diffraction and Fourier transform infrared spectroscopy to determine their phase purity, degree of crystallinity, crystallite size and functional groups. Standard Analysis of variance (ANOVA) showed relatively high contribution of Sr⁺² and Zn⁺² doping in changing the crystallinity and crystal size of HA compared to the effect of Ag⁺ and F^- doping. Our analysis demonstrated strong interaction between dopants at binary level doping, while ternary and quaternary doping of elements did not exhibit any interaction in influencing the crystallinity and crystallite size of HA. In general, multi-ion doping in HA found to decrease its crystallinity from 92% to 72% (max.), but enhance the hardness, depending on the type and concentration of doping element. Similarly, a minimum crystallite size of 31?nm was achieved with some binary compositions and other combinations resulted in crystallite sizes up to 59?nm. The compositions that ensure desired crystallinity and crystallite size can also provide high hardness. Our results can be used to tailor the composition of HA in achieving desired functional properties, dependent on crystallinity and crystallite size, such as strength, bioactivity and degradation to suit variety of implant applications.     

On the effect of channel spacing,launch power,and regenerator placement on the design of mixed-line-rate optical networks

Due to the increasing heterogeneity and the growing volume of traffic, telecom backbone networks are going through significant innovations. Wavelength-division multiplexed (WDM) optical networks can now cost-effectively support the growing heterogeneity of traffic demands by having mixed line rates (MLR) over different wavelength channels.The coexistence of wavelength channels with different line rates, e.g., 10/40/100 Gbps, in the same fiber brings up various design issues: in this study, we focus on (1) choice of channel spacing; (2) choice of launch power; and (3) regenerator placement. Channel spacing affects the signal quality in terms of bit-error rate (BER), and hence affects the maximum reach of lightpaths, which is a function of line rates. Various approaches to set an opportunistic width of the channel spacing can be considered, viz., (i) uniform fixed channel spacing specified by the ITU-T grid (typically 50 GHz); (ii) different channel spacing for different line rates; or (iii) optimal value of channel spacing for all line rates that leads to minimum cost.The launch optical power of a signal is another important parameter that affects the network cost. Adjacent channels on different line rates, especially 10 Gbps and 100 Gbps, may exhibit serious degradation of signal quality and optical reach for both the channels due to cross-phase modulation (XPM) between them. Launch power plays a role in such a scenario as it governs the BER by affecting both the signal power and the noise power due to XPM. Moreover, intelligent choice of launch powers on different line rates can significantly reduce the number of regenerators required in the network. The tradeoff between placement of regenerators and choice of launch power is an important problem to address for MLR network design.In this work, we investigate the effects of channel spacing and launch optical power by evaluating the cost of a MLR network for different values of these parameters. We also study the interplay between regenerator placement and launch power. Our results show that (a) it is possible to identify optimal values of channel spacing for a minimum-cost MLR network design, and (b) controlling the power of 10 Gbps and 100 Gbps channels shows maximum sensitivity to the network cost.     

Ab Initio‐Based Prediction of Phase Diagrams: Application to Magnetic Shape Memory Alloys

An ultimate goal of material scientists is the prediction of the thermodynamics of tailored materials solely based on first principles methods. The present work reviews recent methodological developments and advancements providing thereby an up‐to‐date basis for such an approach. Key ideas and the performance of these methods are discussed with respect to the Heusler alloy Ni–Mn–Ga – a prototype magnetic shape‐memory alloy of great technological interest for various applications. Ni–Mn–Ga shows an interesting and complex sequence of phase transitions, rendering it a significant theoretical challenge for any first principles approach. The primary goal of this investigation is to determine the composition dependence of the martensitic transition temperature in these alloys. Quasiharmonic phonons and the magnetic exchange interactions as well as the delicate interplay of vibrational and magnetic excitations are taken into account employing density functional theory.     

Systematic approach to treat chronic osteomyelitis through localized drug delivery system: Bench to bed side

Chronic osteomyelitis is a challenging setback to the orthopedic surgeons in deciding an optimal therapeutic strategy. Conversely, patients feel frustrated of the therapeutic outcomes and development of adverse drug effects, if any. Present investigation deals with extensive approach incorporating in vivo animal experimentation and human application to treat chronic osteomyelitis, using antibiotic loaded porous hydroxyapatite scaffolds. Micro- to macro-porous hydroxyapatite scaffolds impregnated with antibiotic ceftriaxone–sulbactam sodium (CFS) were fabricated and subsequently evaluated by in vivo animal model after developing osteomyelitis in rabbit tibia. Finally 10 nos. of human osteomyelitis patients involving long bone and mandible were studied for histopathology, radiology, pus culture, 3D CT etc. up to 8–18 months post-operatively. It was established up to animal trial stage that 50N50H samples [with 50–55% porosity, average pore size 110 μm, higher interconnectivity (10–100 μm), and moderately high drug adsorption efficiency (50%)] showed efficient drug release up to 42 days than parenteral group based on infection eradication and new bone formation. In vivo human bone showed gradual evidence of new bone formation and fracture union with organized callus without recurrence of infection even after 8 months. This may be a new, alternative, cost effective and ideal therapeutic strategy for chronic osteomyelitis treatment in human patients.     

Improved properties of hydroxyapatite–carbon nanotube biocomposite: Mechanical,in vitro bioactivity and biological studies

The present work describes a simple shear mixing technique for developing a hydroxyapatite (HAp)–carbon nanotube (CNT) nanocomposite and the effect of reinforcement on the physical, mechanical, in vitro bioactivity and biological properties of HAp. XRD and FTIR confirmed that the main phase of the composites is HAp. HRTEM images demonstrated the formation of a two-dimensional nanocomposite structure, whereas FESEM images indicated the formation of nanosized HAp grains featuring sporadically distributed CNT molecules. No major phase changes in HAp were observed with up to 5% added CNT. However, adding more than 1% CNTs caused an increase in internal crystal strain and increased substitution of CO₃²⁻ for OH⁻ and PO₄³⁻ groups in pure HAp. The average crystallite size increased from ~46 nm to ~100 nm with only 0.5% added CNT, remained nearly unaffected up to 2% CNTs thereafter and suddenly decreased at 5% CNTs (~61 nm). The FESEM and HRTEM images clearly showed the attachment of MWCNT chains on HAp grains, which directly affected the samples' fracture toughness and flexural strength. Of the samples, 1% showed maximum values of K_1C, whereas 5% showed maximum values of HV and three-point bending flexural strength. The in vitro bioactivity indicated increased apatite formation on the sample surface up to 1% CNTs after 24 weeks. However, adding 2% and 5% CNTs resulted in a manifold increase in apatite formation up to 12 weeks, after which dissolution increased up to 24 weeks, possibly due to increased substitution of CO₃²⁻ for OH⁻ and PO₄³⁻ groups. This result is confirmed by the FTIR studies. For all added CNT contents, all samples exhibited high haemocompatibility. However, there was a compromise between the observed mechanical properties and in vitro bioactivity studied up to 24 weeks, and care must be taken before selecting any final application of the nanocomposites.     

Parametric analysis on electrochemical discharge machining of silicon nitride ceramics

The electrochemical discharge machining (ECDM) process has a potential in the machining of silicon nitride ceramics. This paper describes the development of a second order, non-linear mathematical model for establishing the relationship among machining parameters, such as applied voltage, electrolyte concentration and inter-electrode gap, with the dominant machining process criteria, namely material removal rate (MRR), radial overcut (ROC) and thickness of heat affected zone (HAZ), during an ECDM operation on silicon nitride. The model is developed based on response surface methodology (RSM) using the relevant experimental data, which are obtained during an ECDM micro-drilling operation on silicon nitride ceramics. We also offer an analysis of variance (ANOVA) and a confirmation test to verify the fit and adequacy of the developed mathematical models. From the parametric analyses based on mathematical modelling, it can be recommended that applied voltage has more significant effects on MRR, ROC and HAZ thickness during ECDM micro-drilling operation as compared to other machining parameters such as electrolyte concentration and inter-electrode gap.