CuF2 as Reversible Cathode for Fluoride Ion Batteries

In the search for novel battery systems with high energy density and low cost, fluoride ion batteries have recently emerged as a further option to store electricity with very high volumetric energy densities. Among metal fluorides, CuF₂ is an intriguing candidate for cathode materials due to its high specific capacity and high theoretical conversion potential. Here, the reversibility of CuF₂ as a cathode material in the fluoride ion battery system employing a high F^? conducting tysonite‐type La_0.9Ba_0.1F_2.9 as an electrolyte and a metallic La as an anode is investigated. For the first time, the reversible conversion mechanism of CuF₂ with the corresponding variation in fluorine content is reported on the basis of X‐ray photoelectron spectroscopy measurements and cathode/electrolyte interfacial studies by transmission electron microscopy. Investigation of the anode/electrolyte interface reveals structural variation upon cycling with the formation of intermediate layers consisting of i) hexagonal LaF₃ and monoclinic La₂O₃ phases in the pristine interface; ii) two main phases of distorted orthorhombic LaF₃ and monoclinic La₂O₃ after discharging; and iii) a tetragonal lanthanum oxyfluoride (LaOF) phase after charging. The fading mechanism of the cell capacity upon cycling can be explained by Cu diffusion into the electrolyte and side reactions due to the formation of the LaOF compound.     

Distributed BLAST with relay selection for multi‐antenna AF relaying

By examining the diversity–multiplexing tradeoff (DMT) of an amplify‐and‐forward (AF) multi‐antenna multi‐relay network, a procedure to select the optimal number of relays and relay candidates is established. Subsequently, a distributed BLAST transmission scheme in conjunction with successive nulling and cancellation at destination is proposed to achieve the optimal DMT. Illustrative results indicate that the proposed method can significantly enhance the outage probability performance, and for a selected number of relays in use, the performance enhancement can be further improved by increasing the number of available relays in the AF network. Copyright © 2010 John Wiley & Sons, Ltd.     

Massive ovarian enlargement in primary hypothyroidism

OBJECTIVE: To report a case of ovarian cyst formation and myxedematous infiltration of the ovary in a subject with primary hypothyroidism. DESIGN: Retrospective case report. SETTING: University hospital. PATIENT(S): A 16-year-old female adolescent with pelvic pain, galactorrhea, irregular menses, and ovarian cysts on pelvic examination. INTERVENTION(S): Laparotomy with bilateral ovarian wedge resection and thyroid replacement therapy. MAIN OUTCOME MEASURE(S): Ovarian histopathology, thyroid function tests, and menstrual history. RESULT(S): Resolution of patient's pain, galactorrhea, and resumption of normal menses. CONCLUSION(S): Ovarian cyst formation may accompany primary hypothyroidism in the child with accelerated or delayed sexual maturation. To date, the underlying pathophysiology of the morphological changes in the ovary remain enigmatic. This case report provides the first insight into the actual histologic changes that occur in ovaries of subjects with primary hypothyroidism without secondary ovarian pathology such as torsion. There is clear evidence of myxedematous infiltration into the ovarian stroma without luteinization of the theca interna. These microscopic findings suggest that local changes occurring independent of gonadotropin stimulation may contribute significantly to altered morphology of the ovaries in primary hypothyroidism.     

An analysis of the performance of ARQ schemes for integrated traffic satellite-switched SFH and DS CDMA networks

The delay and throughput performance of satellite-switched Slow Frequency Hopping CDMA network for simultaneous voice and data transmission is analyzed and compared to that of a DS-CDMA system. Two ARQ schemes are suggested for data while Forward Error Correction using the same encoder is used for voice packets. The queueing analysis assumes priority for voice and two models for voice traffic are used (Markovian and IPP). The probability of successful packet transmission is derived for all systems as a function of traffic load allowing us to evaluate the systems using delay, throughput, and voice packet loss as figures of merit. Numerical results show that while voice delay is minimal DS CDMA is much more effective then SFH CDMA in all cases. One interesting result is that SFH systems perform better with S/W schemes and achieve a higher maximum throughput. It is also observed that the IPP and Markovian models gave similar results.This work was supported by an NSERC CRD (Collaborative Industrial Research and Development grant,) with Spar Aerospace, Quebec, Canada     

Adaptive combined DFE/MLSE techniques for ISI channels

By embedding a decision-feedback equalizer (DFE) into the structure of a maximum-likelihood sequence estimator (MLSE), an adaptive combined DFE/MLSE scheme is proposed. In this combined DFE/MLSE, the embedded DFE has three functions: (i) prefiltering the received signals and truncating the equivalent channel response into the desired one, (ii) compensating for channel distortions, and (iii) providing the MLSE detector with predicted values of input signals. Since the embedded MLSE detector operates on the predicted signals the detected symbols at the output of the DFE/MLSE do not suffer any delay and can be directly fed back into the embedded DFE so that the error propagation, which usually takes place in a conventional DFE, can be greatly reduced. Analytical and simulation results indicate that the performance is significantly improved by the DFE/MLSE compared to the conventional DFE while its computation complexity is much less than that of the conventional MLSE receiver. The combined DFE/MLSE can use different adaptive structures (block-updating, sliding window updating or symbol-by-symbol updating) to meet different performance objectives. Moreover, the proposed DFE/MLSE provides a trade-off between performance and complexity with a parameter m representing the MLSE detection depth as well as the number of predicting steps of the embedded DFE. For some particular values of m, this scheme is capable of emulating the conventional DFE, MLSE-VA, adaptive LE-MLSE equalizer, adaptive DDFSE, and adaptive BDFE without detection delay     

Sur la dégradation thermique du polychlorure de vinyle. V. Stabilité thermique de polyméres semicristallins

The thermal dehydrochlorination of semicrystalline, but rather low molecular weight, PVC fractions, prepared by ionic polymerization catalyzed by tert-butylmagnesium chloride was studied under an inert atmosphere and compared with that of commercial polymer. When the samples are in powder form, the crystallinity of some fractions, which are insoluble at room temperature in all the usual solvents for PVC, induces a tremendous thermal stability, which is observed so long as the temperature is under the melting point of the sample. In dilute solution, the dehydrochlorination of all the samples is much slower, but the differences between the samples are less important; besides, a catalytic effect of some metallic impurities is observed. This catalytic effect is chiefly relative to a process of intermolecular condensation which causes the formation of a labile tertiary chlorine structure and so initiates or accelerates the purely thermal chain dehydrochlorination. It is suggested that, besides the crystallization and the catalytic effects, the configuration of the structural units could be an important factor in the course of the dehydrochlorination process.     

Soldier defense secretions of malaysian free-ranging termite of the genusLacessititermes (Isoptera,Nasutitermitinae)

Soldiers of free-ranging termites of the genusLacessititermes (Isoptera, Nasutitermitinae) secrete from their frontal glands a mixture of monoterpenes, sesquiterpenes, and diterpenes.Lacessititermes ransoneti, L. laborator, andL. species A produce species-specific secretions, the composition being most complex forL. laborator. Apart from known mono- and dihydroxytrinervitadienes, the following new diterpenes were isolated and tentatively assigned as trinervita-1(15),8(19)-dien-2,3,9,14-tetraol 2,3,14-O-triacetate, trinervita-1(15),8(19)-dien-2,3,9,14-tetraol 2,3,14-O-triacetate, 2,3,9, 14-tetraacetoxy-1 (15), 8(19)-trinervitadiene, and 2,3,11,13-tetraacetoxy-1(15),8(19)-trinervitadiene. Data on intragenus chemical variations were subjected to canonical discriminant analysis and genetic distances among the species were calculated to depict intragenus identities and affinities.     

C0 solid elements for materials with strain gradient effects

Experiments conducted by various researchers in the past few decades have shown that materials display strong size effects when the material and characteristic length scales associated with non‐uniform plastic deformation are of the same order at micron and submicron levels. The state of stress under such a condition was observed to be a function of both strain and strain gradient. The meso‐scale constitutive relation taking into account Taylor dislocation theory is briefly described. The conventional theory of mechanism‐based strain‐gradient (CMSG) plasticity incorporating the intrinsic material length scale is adopted in the formulation of a series of C⁰ solid elements of 20–27 nodes. The model is implemented in ABAQUS, a finite element package via a user subroutine. Convergent studies have been carried for the series of elements with classical as well as CMSG plasticity theories. Numerical results on a bar under constant body force and indentation at submicron level reinforce the observation that materials are significantly strengthened for deformation at micron and submicron levels and the effects of strain gradient cannot be ignored without significant loss of the accuracy of the results. Copyright © 2005 John Wiley & Sons, Ltd.     

2-D optical CDMA networks using MWPM, double hard limiters and modified carrier-hopping prime sequences

This paper presents a two-dimensional optical code division multiple access (2-D-OCDMA) scheme using multiwavelength pulse modulation (MWPM), double optical hard limiters (DHL), and modified carrier-hopping prime sequences (MCHP) to increase the achievable system capacity. Design criteria to reduce multiaccess interference (MAI) are established and indicate that suitable signature sequences for 2-D-OCDMA/MWPM must have good cross-correlation property in terms of both time shift and wavelength shift. Performance analysis of 2-D-OCDMA/MWPM/DHL systems in the presence of MAI and photo detector shot noise is developed. Simulation and analytical results are in very good agreement and indicate that the proposed 2-D-OCDMA/MWPM/DHL systems using MCHP sequences can offer a much larger capacity than others, suitable for applications in broadband fiber-optic access networks.