Axisymmetric static and dynamic buckling of orthotropic shallow spherical cap with circular hole

Nonlinear axisymmetric static and dynamic buckling of clamped isotropic and cylindrically orthotropic elastic cap with central circular hole have been investigated. The governing equations are expressed in terms of normal displacement ω and stress function ψ. The orthogonal point collocation method has been used in the space domain and Newmark-β scheme in the time domain. The cases of shallow cap with free hole and with a hole plugged by rigid central mass are considered. Analysis has been carried out for uniformly distributed load and a ring load at the hole. Dynamic load is taken as a step function load. Detailed new results for static and dynamic buckling loads have been presented for the isotropic and orthotropic cases.     

DVDs: Much Needed “Shot in the Arm” for Video Servers

The release of DVD-ROMs (Digital Versatile Disk—Read Only Memory), capable of storing an entire 133 minute MPEG-2 movie, coupled with the gradual deployment of high speed networks will give a much needed impetus to Video-on-Demand systems, especially movie-on-demand services. Various memory components such as DVD-ROMs, magnetic RAID towers, and RAM are available, each with different storage and bandwidth capabilities, and each with different costs. To design a video server, we need to optimize the cost factor, yet meet the massive storage, high bandwidth and continuity requirements of video stream delivery.In the first part of this paper we compare DVD-ROM and RAID systems on the basis of two factors—a storage factor and a bandwidth factor. We work out relations to calculate capacity requirements and costs, of these systems given the demands of video delivery. We then propose an architecture for a video server where we deploy three layers of memory functioning as video pumps: DVD-ROM towers, RAID towers, and RAM. We then work out expressions to determine the migration strategy of a movie between these layers of storage so as to optimize on the cost of storage while satisfying the performance requirements. We then show the method by which the amount of storage required for each type of memory in the three layers can be fixed, knowing the usage pattern.In the second part of the paper, we discuss the implementation of a video pump where there is a need to integrate scheduling, admission control, VBR stream management, and handling of VCR-like requests such as fast-forward, fast-reverse and pause. We first work out general relations for calculation of the service time of a request knowing the seek overheads and playback rates. We then show that, surprisingly, the C-SCAN algorithm, which incurs the least amount of seek overhead and therefore has a lesser cycle time, is twice as efficient as SCAN in terms of buffer space requirements. We then propose a full-load admission control and scheduling algorithm that operates on a constant cycle time basis. We test the validity of this scheme though a the simulator which we have built based on our disk model and use it to extract parameters such as disk bandwidth utilization factor and buffer sizes needed for a VBR load scenario.     

Stone–Wales Defect in Graphene

2D graphene the most investigated structures from nanocarbon family studied in the last three decades. It is projected as an excellent material useful for quantum computing, artificial intelligence, and next generation advanced technologies. Graphene exists in several forms and its extraordinary thermal, mechanical, and electronic properties, principally depend on the kind of perfection of the hexagonal atomic lattice. Defects are always considered as undesired components but certain defects in graphene could be an asset for electrochemistry and quantum electronics due to the engineered electronclouds and quantum tunnelling. The authors carefully discuss the Stone-Wales imperfections in graphene and its derivatives comprehensively. A specific emphasis is focused on the experimental and theoretical aspects of the Stone-Wales defects in graphene with respect to structure-property relationships. The corroboration of extrinsic defects like external atomic doping, functionalization, edge distortion in the graphene consisting of Stone-Wales imperfections, which are very significant in designing graphene-based electronic devices, are summarized.     

Seismic response of a continuous bridge with bearing protection devices

Unseating of bridges during earthquakes results from the failure of bearings and insufficient seat length. In case of elastomeric bearings, large deformations of the superstructure occur, under severe earthquake ground motions and additional protection measures are necessary. The combination of a displacement restraining device with the elastomeric bearing can prevent bearing failure. This paper evaluates the performance of four different types of protection devices to limit the displacement of the superstructure during earthquakes: (1) rigid stopper device, (2) yielding stopper device, (3) steel restrainer, and (4) superelastic shape memory alloy (SMA) restrainer. Analytical models for all the protection devices have been developed and seismic response of an existing bridge with elastomeric bearings and different protection devices has been evaluated for five strong ground motion records scaled in the frequency domain. The results show that all the protection devices have comparable performance in preventing the failure of bearing during an earthquake.     

Platelet and neutrophil distributions in pump oxygenator circuits. III. Influence of nitric oxide gas infusion

The authors used quantitative gamma scintigraphy to evaluate the influence of nitric oxide gas on platelet and neutrophil deposition in Cobe Duo microporous oxygenators during cardiopulmonary bypass (CPB). The effects of nitric oxide gas on circulating platelet and neutrophil counts and platelet function also were assessed. Animals were prepared by standard methods. Cells were harvested, labeled (111 In platelet and 99mTc neutrophil), infused, and recirculated. Nitric oxide gas, a guanylate cyclase pathway promoter, was infused int he Duo gas port at 500 ppm (t = 0-60 min), increased to 1,000 (t = 60-80 min), and stopped (final, 10 min). Images were taken at 10-15 min intervals during CPB. Standard isotope image corrections were made. No differences between nitric oxide gas and control experiments were observed for flow, pressure, hematocrit, or replacement volume. Nitric oxide gas infusion significantly (p < 0.05) reduced both platelet adherence to the oxygenator and in vitro platelet aggregation. Neutrophil adhesion tended to be lower, and circulating platelet and neutrophil counts tended to be higher with nitric oxide gas infusion. Results of in vitro aggregometry studies using rabbit platelets indicate that the class V phosphodiesterase inhibitor zaprinast can strongly enhance the inhibitory effects of nitric oxide. The authors conclude nitric oxide gas is a promising platelet sparing agent in the setting of CPB.     

IL-3 enhances both presentation of exogenous particulate antigen in association with class I major histocompatibility antigen and generation of primary tumor-specific cytolytic T lymphocytes

Recent studies have reported that APC can present particulate exogenous Ag in the context of class I MHC to CD8+ CTL, and our laboratory demonstrated that IL-3 could enhance CTL generation to exogenous Ag. In this paper, we wished to determine whether presentation of particulate Ag could be enhanced by IL-3. A T cell hybridoma, B3Z86/90.14 (B3Z) restricted to Ova/Kb, was used as an indicator for presentation of particulate Ag with class I MHC. When activated, this hybridoma expresses lacZ, allowing a simple colorimetric measurement of Ag-specific T cell stimulation. We demonstrated that bone marrow cells stimulated by IL-3 in vivo and in vitro exhibited significantly increased presentation of exogenous OVA linked to beads. Lysate from OVA-transfected line 1 murine lung adenocarcinoma cells (line 1/OVA) was also presented by IL-3-stimulated bone marrow cells, suggesting that these APC can process tumor fragments or debris. Studies using TAP1/2-deficient mice and Ag presentation inhibitors indicate that this exogenous Ag presentation is mediated via the conventional class I MHC pathway. Adoptive transfer of IL-3-stimulated bone marrow cells pulsed with lysate from line 1/OVA tumor cells into naive recipient mice led to the generation of a potent CTL response. These observations indicate that use of such cells may provide a new avenue for development of tumor vaccines.