A preliminary survey of radio-frequency interference over the U.S. in Aqua AMSR-E data

A spectral difference method is used to quantify the magnitude and extent of radio-frequency interference (RFI) observed over the United States in the Aqua AMSR-E radiometer channels. A survey using data from the AMSR-E instrument launched in May 2002 shows the interference to be widespread in the C-band (6.9 GHz) channels. The RFI is located mostly, but not always, near large highly populated urban areas. The locations of interference are persistent in time, but the magnitudes show temporal and directional variability. Strong and moderate RFI can be identified relatively easily using an RFI index derived from the spectral difference between the 6.9- and 10.7-GHz channels. Weak RFI is difficult to distinguish, however, from natural geophysical variability. These findings have implications for future microwave sensing at C-band, particularly over land areas. An innovative concept for radiometer system design is also discussed as a possible mitigation approach.     

The WindSat spaceborne polarimetric microwave radiometer: sensor description and early orbit performance

The global ocean surface wind vector is a key parameter for short-term weather forecasting, the issuing of timely weather warnings, and the gathering of general climatological data. In addition, it affects a broad range of naval missions, including strategic ship movement and positioning, aircraft carrier operations, aircraft deployment, effective weapons use, underway replenishment, and littoral operations. WindSat is a satellite-based multifrequency polarimetric microwave radiometer developed by the Naval Research Laboratory for the U.S. Navy and the National Polar-orbiting Operational Environmental Satellite System Integrated Program Office. It is designed to demonstrate the capability of polarimetric microwave radiometry to measure the ocean surface wind vector from space. The sensor provides risk reduction for the development of the Conical Microwave Imager Sounder, which is planned to provide wind vector data operationally starting in 2010. WindSat is the primary payload on the Department of Defense Coriolis satellite, which was launched on January 6, 2003. It is in an 840-km circular sun-synchronous orbit. The WindSat payload is performing well and is currently undergoing rigorous calibration and validation to verify mission success.     

Ureteritis and cholecystitis: two unusual manifestations of cytomegalovirus disease in renal transplant recipients

BACKGROUND: Common clinical manifestations of cytomegalovirus (CMV) infection include flu-like symptoms with fever, diarrhea, leukopenia, and elevated liver enzymes. Diagnosis is made by detection of the virus by buffy-coat blood culture or by polymerase chain reaction (PCR) analysis. METHODS: Here we describe two renal transplant recipients who presented with unusual manifestations of CMV disease (cholecystitis and ureteritis). In both patients, no symptoms or signs of systemic CMV infection were present, and they were thought to have other common causes for cholecystitis and ureteral obstruction. RESULTS: Retrospective analysis of peripheral blood by PCR analysis was positive for CMV DNA. Histologic examination of the resected gall bladder and stenotic ureteric segment showed CMV inclusions, confirmed subsequently by in situ hybridization. Thus, we report that CMV infection may present with acute cholecystitis or ureteral obstruction without its classical clinical symptoms. CONCLUSIONS: Because CMV infection is common in transplant patients, the atypical manifestations of CMV should be considered in the differential diagnosis of posttransplant complications. Detection of CMV DNA in the peripheral blood by PCR analysis may help identify these patients.     

Reconstruction of the long bones of the legs in children via free vascularized transplant of the fibula after resection for sarcoma

Nineteen children were operated on between 1985 and 1994. All the patients presented a sarcoma of long bones: osteosarcoma: 12 and Ewing's sarcoma: 7. They were operated on: resection and reconstruction of the long bones with a free vascularised fibula. Pre and post-operative chemotherapy was used. The average follow-up was 3 years (between 10 years and 1 year). The mean bone defect was 20 cm (between 32 and 11 cm). Boys were more frequently encountered [12]. Average age was 9.5 years. The pathological bone was: femur: 14, tibia: 4, humerus 1. The approach needs usually two incisions for femoral bone: the internal incision allows us to prepare the recipient vessels: deep femoral vessels in 11 cases. In 18 cases, union occurred in less than 14 months. One case of pseudarthrosis occurred. Immediate follow-up was simple in 17 cases. Infection was observed in 2 cases. Secondly, the most frequent complications were: fracture of the fibula: 6 cases, vicious cal: 2 cases; delayed union: 6 cases; stiffness: 2 cases. One patient died later from pulmonary metastasis. Solid osteosynthesis of the member and of the free vascularised fibula permit to shorten these delays. Success depends on two criteria: the graft thickening of the fibula and union of the fibula at both ends. The micro vascular anastomoses must be excellent. Twelve children had bone union with only one operation. In the 6 cases of delayed union, secondary bone grafts give consolidation. The comparison of this technique with standard treatment showed an evident superiority of the free vascularised fibula transplant in extensive defects of bone. The fibula is a life bone which permits rapid union with a short hospitalization, a quick recovery and an early return to school. Free vascularised fibula permit to ameliorate the quality of survival.     

A new methodology to compute stabilizing control laws for continuous‐time LTV systems

This paper is devoted to the problem of computing control laws for the stabilization of continuous‐time linear time‐varying systems. First, a necessary and sufficient condition to assess the stability of a linear time‐varying system based on the norm of the transition matrix computed over a sequence of successive finite‐time intervals is proposed. A link with a stability condition for an equivalent discrete‐time model is also established. Then, 3 approaches for the computation of stabilizing state‐feedback gains are proposed: a continuous‐time technique, ie, directly derived from the stability condition, not suitable for numerical implementation; a method based on the stabilization of the discrete‐time equivalent model along with a transformation to generate the desired continuous‐time gain; and the computation of stabilizing gains for a set of periodic discrete‐time systems. Finally, by adapting one of the existing methods for the stabilization of periodic discrete‐time systems, an algorithm for the computation of a stabilizing state‐feedback continuous‐time gain is proposed. A numerical example illustrates the validity of the technique.     

Physical and mechanical properties of polyethylene for pipes in relation to molecular architecture. II. Short‐term creep of isotropic and drawn materials

Tensile drawing and short‐term creep of ethylene/α‐olefin copolymers having bimodal (BM) molar weight distribution are studied in comparison with unimodal (UM) copolymers of similar crystallinity. The natural draw ratio and viscoelastic recovery upon unloading strongly suggest that BM copolymers have more tie chains and chain entanglements than corresponding UM copolymers. The incorporation of co‐units in the longest chains of BM copolymers is ascribed a major role on these topological changes. Creep of isotropic materials shows lower compliance for BM copolymers in parallel with higher‐durability grades. This is attributed to a better “macromolecular network efficiency.” The creep behavior of strain‐hardened samples, which is assumed to simulate the mechanical behavior of craze fibrils at the tip of a propagating crack, reveals similar trends. The better fibril strength in BM copolymers is again ascribed to a better network efficiency. Necked samples display an odd behavior of higher compliance at low stress and lower compliance at high stress for BM copolymers compared with the behavior of UM counterparts. This is associated with the exhaustion of viscoelastic capabilities with increasing draw ratio and stress. The phenomenon is discussed in relation to cavitation. A short‐term creep test is proposed for comparative prediction of long‐term behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2308–2317, 2002     

Mixed nickel-aluminium oxides catalysts for the nitroxidation of toluene by no into benzonitrile

This paper describes the catalytic properties (activities, selectivities and stabilities with time on stream) of nickel oxide-alumina aerogels and xerogels, towards the transformation of toluene by NO into benzonitrile at 440°C in a differential flow reactor. The stability of the catalysts depends upon the NiO content. When the ratio Ni/Al increases to unity, the catalysts (aerogel as well as xerogel) are very stable with time on stream and are active and selective like pure nickel oxide. The latter is indeed initially active and selective, but very unstable with time on stream. A redox model is proposed to explain the reaction mechanism.     

A colorimetric assay for measuring cell-free and cell-bound cholesterol oxidase

Cholesterol oxidase (cholesterol:oxygen oxidoreductase, EC 1.1.3.6) catalyzes the conversion of sterol Δ⁵-3β-alcohol to the corresponding Δ⁴-3-ketone with the reduction of oxygen to hydrogen peroxide.Rhodococcus species GK 1, a soil isolated microbe, produces an extracellular and a membrane-bound cholesterol oxidase; the latter is bound to the outer surface of the microbial cell membrane. A simple and sensitive assay is described to measure the two enzyme types; no enzyme extraction is needed for measuring the membrane-bound cholesterol oxidase. In this assay, hydrogen peroxide is reduced by the chromogen 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in the presence of horseradish peroxidase, and the increased absorbance is followed continuously at 600 nm (ε_m = 1.82×10⁴ M⁻¹·cm⁻¹ at pH 7.0 and 30°C). The standardized assay medium contained 46.9 mM sodium-potassium phosphate buffer pH 7.0, 0.16% Triton X-100, 312.5 μM ABTS, 50 μg peroxidase (12.5 units at 25°C), 6.25% isopropanol, 306.3 μM cholesterol or other sterols (kept in solution with isopropanol), and cholesterol oxidase. Oxidation of one molecule of cholesterol by cholesterol oxidase gives one molecule of hydrogen peroxide which reacts with two molecules of ABTS. The method is reproducible and the results correlate well with those obtained by measuring the absorbance of Δ⁴-cholest-3-one at 240 nm (ε_m = 1.40×10⁴ M⁻¹·cm⁻¹ at pH 7.0 and 30°C) and by the method of Allainet al. (Clin. Chem. 20, 470–475, 1974). In terms of efficiency, simplicity, and time saved, this coupled assay is expected to be a useful method for monitoring microbial production of cholesterol oxidase on an industrial scale, and for determining cholesterol or other sterols in biological fluids.     

Mixing and micromixing times in the forced vortex region of unbaffled mixing devices

Unbaffied mixing devices are characterized by a very particular hydrodynamics. A well defined depression in the liquid surface is formed, resulting from the combined vortex established in the liquid. The combined vortex is composed of one central Forced Vortex Region (FVR) and one annular free vortex region. Because the FVR behaves like a confined mixing zone, this region inside an unbaffled mixing device appears to be quite interesting to carry out certain chemical reactions. In this paper the influence of operating conditions on the mixing time of two reagent feed streams arriving continuously in the FVR of unbaffled mixing devices is investigated. Process parameters investigated are?: stirrer speed, reagent flow rates and feed pipe position. Mixing time correlations are established, which are useful for the scale‐up of this reactor.