Approximately optimal trees for group key management with batch updates

We investigate the group key management problem for broadcasting applications. Previous work showed that, in handling key updates, batch rekeying can be more cost effective than individual rekeying. One model for batch rekeying is to assume that every user has probability p$p$ of being replaced by a new user during a batch period with the total number of users unchanged. Under this model, it was recently shown that an optimal key tree can be constructed in linear time when p$p$ is a constant and in O(n⁴)$O\left(n^4\right)$ time when p→0$p\to 0$. In this paper, we investigate more efficient algorithms for the case p→0$p\to 0$, i.e., when membership changes are sparse. We design an O(n)$O\left(n\right)$ heuristic algorithm for the sparse case and show that it produces a nearly 2-approximation to the optimal key tree. Simulation results show that its performance is even better in practice. We also design a refined heuristic algorithm and show that it achieves an approximation ratio of 1+?$1+?$ for any fixed ?>0$?>0$ and n$n$, as p→0$p\to 0$. Finally, we give another approximation algorithm for any p∈(0,0.693)$p\in (0,0.693)$ which is shown to be quite good by our simulations.     

Design of a dual stage actuator tape head with high-bandwidth track following capability

As tape recording density increases, high-frequency track following capability of the tape head actuator becomes more important. This paper details the mechanical design and experimental analysis of a dual state actuator tape head. The dual stage actuator design combines a traditional voice coil motor for low frequency track following with a piezoelectric actuator for high-frequency track following. Non-parametric and parametric modeling techniques are used in the analysis of the dual stage actuator. The performance of the dual stage actuator head shows good correlation with the model and will enable improved track following capability for future high-performance tape drives.     

Virtual Graphics for Broadcast Production

The ability to mix and merge video images with interactive 3D graphics offers the possibility for TV content to evolve in line with the trend for entertainment media to become ever more computer-centric, making it more accessible to the "gaming generation."     

Towards improving the accuracy of opium yield estimates with remote sensing

Yearly estimates of illicit opium production are key metrics for assessing the effectiveness of the counter-narcotics policy in Afghanistan. Poor security often prevents access to sample locations and puts pressure on field surveyors, resulting in biased sampling and errors in data recording. Supportive methods using aerial digital photography for improving yield estimates were investigated in the UK in 2004, 2005, and 2010. There were good empirical relationships between normalized difference vegetation index and poppy yield indicators (mature capsule volume and dry capsule yield) for individual fields. The results suggested a good generalized relationship across all sampled fields and years (R² > 0.70) during the 3–4 week period including poppy flowering. Regression estimates using this relationship with the imagery counteracted bias in the sample estimate of yield, reduced sample error, and enabled the production of detailed maps showing the poppy yield distribution. The application of this approach using very-high-resolution satellite imagery was investigated in the context of the annual opium survey in Afghanistan. Initial results indicated the potential for bias correction of yield estimates using a smaller and targeted collection of ground observations as an alternative to random sampling.     

Conservation of closed loops

The closed loop hypothesis of Berezovsky and Trifonov implicates the closure of loops of length 25-35 through hydrophobic interactions at the 'locks' as a key event in protein folding. The hypothesis is supported by published analyses of nine major superfolds. Here, we have generated multiple sequence alignments for the nine superfolds with PDB codes lthb, 1ilb, 256b, 2rhe, 1aps, 2stv, 4fxn (2fox), lubq and 7tim and have analysed the degree of conservation at the loop ends. Seventy percent of these loop ends are found to be well conserved and the peak in the distribution of distances between these well conserved regions lies at around 25 residues; both observations are consistent with the Berezovsky and Trifonov's hypothesis.     

Diagnostic biomarkers differentiating metastatic melanoma patients from healthy controls identified by an integrated MALDI-TOF mass spectrometry/bioinformatic approach

The prognosis of advanced metastatic melanoma (American Joint Committee on Cancer (AJCC) stage IV) remains dismal with a 5-year survival rate of 6-18%. In the present study, an integrated MALDI mass spectrometric approach combined with artificial neural networks (ANNs) analysis and modeling has been used for the identification of biomarker ions in serum from stage IV melanoma patients allowing the discrimination of metastatic disease from healthy status with high specificities of 92% for protein ions and 100% for peptide biomarkers. Our ANNs model also correctly classified 98% of a blind validation set of AJCC stage I melanoma samples as nonstage IV samples, emphasizing the power of the newly defined biomarkers to identify patients with late-stage metastatic melanoma. Sequence analysis identified peptides derived from metastasis-associated proteins; alpha 1-acid glycoprotein precursor-1/2 (AAG-1/2) and complement C3 component precursor-1 (CCCP-1). Furthermore, quantitation of serum AAG by an immunoassay showed a significant (p<0.001) increase in AAG serum concentration in stage IV patients in comparison with healthy volunteers; moreover; the quantity of AAG plotted against MALDI-MS peak intensity classified the groups into two distinct clusters. Ongoing studies of other disease stages will provide evidence whether our strategy is sufficiently robust to give rise to stage-specific protein/peptide signatures in melanoma.     

Blue rubber bleb nevus syndrome

In the presence of an internal mammary artery graft crossing the mid-sternal line, a median sternotomy may jeopardize the graft and consequently bring a hemodynamic compromise. We describe a case of successful radical pericardiectomy for postoperative constrictive pericarditis using a "T-shaped" thoracotomy in a 68-year-old male patient who had a right IMA graft to the left anterior descending coronary artery.     

Analysis and Experiment of Self-Powered,Pulse-Based Energy Harvester Using 400 V FEP-Based Segmented Triboelectric Nanogenerators and 98.2% Tracking Efficient Power Management IC for Multi-Functional IoT Applications

A self-powered system for the Internet of Things (IoT) is demonstrated for efficient energy harvesting of naturally available mechanical energy. In this system, new contact-separation mode triboelectric nanogenerators (TENGs), based on fluorinated ethylene propylene, are investigated using the segmented multi-TENG configuration to reduce the effect of parasitic capacitance. The TENG extraction is optimized using a unit step excitation involved with the Dawson function to achieve a high voltage (400 V) and a high current (26.6 µA). To fully extract the power of the TENGs, the power management integrated circuit (PMIC) specially designed for adaptively controlled, high-voltage (HV) maximum power point tracking (MPPT) is proposed. The PMIC implemented in a bipolar CMOS-DMOS 180 nm process can handle a wide input range (5–70 V) by consuming 420 nW. The MPPT control allows a wide range of impedance matching from 10 to 300 MΩ, achieving a tracking efficiency of up to 98.2%. The end-to-end efficiency of 88% demonstrates state-of-the-art performance. To supply a higher instantaneous power than that available from the TENGs, a duty-cycling technique is successfully demonstrated. The proposed energy harvesting system provides a promising approach to realizing sustainable and autonomous energy sources for various IoT applications.     

A Cross-Cultural Investigation of Cognitions and Depressive Symptoms in Adolescents.

Adolescents (N=2,272) from Hong Kong and the United States provided information regarding their depressive symptoms, cognitions (self-efficacy, negative cognitive errors, and hopelessness), and stressful events between 2 surveys 6 months apart. Depressive symptoms and hopelessness were higher, and self-efficacy and negative cognitive errors were lower in Hong Kong than in the United Stales. Cognitions were associated with concurrent depressive symptoms and predicted depressive symptoms 6 months later in both cultures. The "reverse" model was also supported with more variance predicted by depressive symptoms to later cognitions than from cognitions to depressive symptoms. There was some support for the hypothesis that self-efficacy is less salient in collective compared with individualistic cultures. These findings extend cognitive theories of depression to a non-Western culture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)