Synthesis of 1-deoxysphingosine derivatives with conformationally restricted pyrrolidinediol head groups

[structure: see text] A family of cyclic 1-deoxysphingolipid derivatives of structure 4 has been designed and synthesized, which may serve as tumorigenesis suppressors for various cancers. Compound 4 is a second-generation analogue developed from sphingosine (1), in which a hydroxyl substituent is moved from C1 to C5 and a methylene is added for conformational rigidity between the C2-nitrogen substituent and C4. The synthetic chemistry for pyrrolidine ring closure at C3-C4 features ring-closing metathesis followed by hydroboration-oxidation.     

High-resolution FTIR spectroscopy of HNSO—Analysis of the highly perturbed ν4, ν6 and 2ν5 bands

We report a rovibrational analysis of the ν₄ and ν₆ fundamentals and the 2ν₅ overtone of HNSO from high-resolution Fourier transform infrared spectra. The ν₆ band (out-of-plane bend) centred at 757.5 cm⁻¹ is c-type. The ν₄ band (HNS bend) centred at 905.9 cm⁻¹ is predominantly a-type with a very weak b-type component (). Numerous global perturbations and localized avoided crossings affecting the v₄ = 1 rotational levels were successfully treated by inclusion of Fermi and c-axis Coriolis resonance terms between v₄ = 1 and v₅ = 2, and a b-axis Coriolis resonance term between v₄ = 1 and v₆ = 1. The latter term gives rise to an avoided crossing with an extraordinary ΔK_a = 5 selection rule. The Fermi resonance between v₄ = 1 and v₅ = 2 gives rise to strong mixing of their rotational wavefunctions in the vicinity of K_a = 18. The resultant borrowing of intensity made it possible for 2ν₅ transitions in the range K_a = 16–19 to be assigned and included in a global rovibrational treatment of all three band systems.     

A Millimeter-Wave (40–45 GHz) 16-Element Phased-Array Transmitter in 0.18-$mu$ m SiGe BiCMOS Technology

This paper demonstrates a 16-element phased-array transmitter in a standard 0.18-mum SiGe BiCMOS technology for Q-band satellite applications. The transmitter array is based on the all-RF architecture with 4-bit RF phase shifters and a corporate-feed network. A 1:2 active divider and two 1:8 passive tee-junction dividers constitute the corporate-feed network, and three-dimensional shielded transmission-lines are used for the passive divider to minimize area. All signals are processed differentially inside the chip except for the input and output interfaces. The phased-array transmitter results in a 12.5 dB of average power gain per channel at 42.5 GHz with a 3-dB gain bandwidth of 39.9-45.6 GHz. The RMS gain variation is < 1.3 dB and the RMS phase variation is < for all 4-bit phase states at 35-50 GHz. The measured input and output return losses are < -10 dB at 36.6-50 GHz, and <-10 dB at 37.6-50 GHz, respectively. The measured peak-to-peak group delay variation is plusmn 20 ps at 40-45 GHz. The output P_-1dB is -5plusmn1.5 dBm and the maximum saturated output power is - 2.5plusmn1.5 dBm per channel at 42.5 GHz. The transmitter shows <1.8 dB of RMS gain mismatch and < 7deg of RMS phase mismatch between the 16 different channels over all phase states. A - 30 dB worst-case port-to-port coupling is measured between adjacent channels at 30-50 GHz, and the measured RMS gain and phase disturbances due to the inter-channel coupling are < 0.15 dB and < 1deg, respectively, at 35-50 GHz. All measurements are obtained without any on-chip calibration. The chip consumes 720 mA from a 5 V supply voltage and the chip size is 2.6times3.2 mm².     

Resource optimization in distributed biometric recognition using wireless sensor network

Distributed, autonomous and energy efficient protocols are best suited for wireless sensor networks, where network needs and events are dynamic. In this paper, a wireless face recognition system with limited resources such as energy, memory and bandwidth is analyzed. The performance of the applications is influenced by the protocol adaptability and quality of information. Performance comparisons are completed using 1. In-network image compression using Contourlet and Wavelet transforms versus raw image data transmission, 2. longevity of sensors versus network throughput. Balancing resource constraints, maintaining network lifetime and throughput is a non-deterministic polynomial computation time problem. Thus a meta-heuristic combinatorial algorithm, based on swarm intelligence, forms the cognitive routing protocol. The network efficiency considers energy consumption, response time, probability of correct acceptance, processing and computation time for wireless image transmission.

Invariants of t-structures and classification of nullity classes

We construct an invariant of t-structures on the derived category of a commutative noetherian ring. This invariant is complete when restricting to the category of complexes with finitely generated bounded homology, and also gives a classification of nullity classes with the same restriction. On the full derived category of Z we show that the class of distinct t-structures do not form a set.     

On the anonymity of some authentication schemes for wireless communications

In 2004, Zhu and Ma proposed a new and efficient authentication scheme claiming to provide anonymity for wireless environments. Two years later, Lee et al. revealed several previously unpublished flaws in Zhu-Ma?s authentication scheme and proposed a fix. More recently in 2008, Wu et al. pointed out that Lee et al.?s proposed fix fails to preserve anonymity as claimed and then proposed yet another fix to address the problem. In this paper, we use Wu et al.?s scheme as a case study and demonstrate that due to an inherent design flaw in Zhu-Ma?s scheme, the latter and its successors are unlikely to provide anonymity. We hope that by identifying this design flaw, similar structural mistakes can be avoided in future designs.     

Antiplasmodial and cytotoxic activities of drimane sesquiterpenes from Canella winterana

The hexane extract from the leaves of Canella winterana exhibited strong activity against the chloroquine sensitive (CQS) strain of Plasmodium falciparum (D10) in vitro (IC50 2.53 microg/mL). Bioassay guided fractionation of this extract has led to the isolation of 5 drimane-type sesquiterpenoids: 9-epideoxymuzigadial, 9-deoxymuzigadial, muzigadial, 3-beta-acetoxypolygodial and the newly isolated hemiacetal, named muzigodiol, with IC50-values of 1.01, 2.19, 0.31, 2.77 and 7.43 microg/mL, respectively. The first four compounds were tested for their cytotoxicity using Chinese Hamster Ovarian (CHO) cells, where they showed IC50-values of 1.82, 33.69, 1.18, and 58.31 microg/mL, respectively. A structure-activity relationship is discussed.     

De novo design and molecular assembly of a transmembrane diporphyrin-binding protein complex

The de novo design of membrane proteins remains difficult despite recent advances in understanding the factors that drive membrane protein folding and association. We have designed a membrane protein PRIME (PoRphyrins In MEmbrane) that positions two non-natural iron diphenylporphyrins (Fe(III)DPP's) sufficiently close to provide a multicentered pathway for transmembrane electron transfer. Computational methods previously used for the design of multiporphyrin water-soluble helical proteins were extended to this membrane target. Four helices were arranged in a D(2)-symmetrical bundle to bind two Fe(II/III) diphenylporphyrins in a bis-His geometry further stabilized by second-shell hydrogen bonds. UV-vis absorbance, CD spectroscopy, analytical ultracentrifugation, redox potentiometry, and EPR demonstrate that PRIME binds the cofactor with high affinity and specificity in the expected geometry.     

Optimized structured treatment interruption for HIV therapy and its performance analysis on controllability

This paper presents dynamic programming therapy to reduce medication and establish long-term immune response against HIV-infection. Understanding HIV-related immune system control enables better HIV therapy without using full-treatments. Discrete regimen and continuous regimen characteristics are compared. Controllability of HIV-related immune system is analyzed for better understanding of optimal control in HIV therapy. Using optimal control provides more effective therapy than the full treatment without interruption in terms of controllability analysis. Case studies indicated the proposed therapy induces long-term nonprogression while preserving high CD4 T-helper cell count and low virus load in HIV-infected patients.     

Determining factors affecting ESD failure voltage using DOE

Factors influencing machine model (MM) ESD failure voltage are investigated in two statistically designed experiments. Several variables (or factors), namely wafer lot, type of ESD handling procedure, pulse polarity order and assembly house are studied. The results are examined using three methods: survival analysis, logistic regression and an empirical approach. Each method can be used to predict the cumulative distribution function (cdf) which is the probability of failure on or before a particular voltage. Survival analysis treats the failure voltage as a response to the settings of the various factors. The failure voltage is analogous to the “failure time”. This method predicts the cdf given the settings of the different variables. In contrast, logistic regression treats voltage as a factor, along with the other variables and will similarly predict the cdf given the settings of all the factors. The empirical approach is used to estimate the cdf using only the distribution of failure voltages for each run in a designed experiment and is not derived from the factor settings. This third approach can be used as a check on the first two.In the first DOE, the factors wafer lot, level of ESD-safe handling, pulse polarity order and their interactions are found to change the predicted median failure voltage from 19 to 34 V, a swing of ±30% from the overall median 26 V. The effect of wafer lot along with the interaction between the level of ESD protection and pulse polarity order are found to be statistically significant. In the second DOE, only the effects of wafer and assembly house are studied. Here, just wafer has a significant effect. The range of ESD failure voltages is much smaller in round 2 (30 to 36 V).Although the failure voltages reported here are relatively low, the methods described herein are general. Thus, the approaches described can be applied to circuits with much higher ESD failure voltages.