Search

To mitigate methane emission from urban natural gas distribution systems, it is crucial to understand local leak rates and occurrence rates. To explore urban methane emissions in cities outside the U.S., where significant emissions were found previously, mobile measurements were performed in 12 cities across eight countries. The surveyed cities range from medium size, like Groningen, NL, to large size, like Toronto, CA, and London, UK. Furthermore, this survey spanned across European regions from Barcelona, ES, to Bucharest, RO. The joint analysis of all data allows us to focus on general emission behavior for cities with different infrastructure and environmental conditions. We find that all cities have a spectrum of small, medium, and large methane sources in their domain. The emission rates found follow a heavy-tailed distribution, and the top 10% of emitters account for 60–80% of total emissions, which implies that strategic repair planning could help reduce emissions quickly. Furthermore, we compare our findings with inventory estimates for urban natural gas-related methane emissions from this sector in Europe. While cities with larger reported emissions were found to generally also have larger observed emissions, we find clear discrepancies between observation-based and inventory-based emission estimates for our 12 cities.

One of the very challenging aspects of Li–S battery development is the fabrication of a sulfur electrode with high areal loading using conventional Li-ion binders. Herein, we report a new multifunctional polymeric binder, synthesized by the free-radical cross-linking polymerization of [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETMAC) and ethylene glycol diacrylate (EGDA) to form poly(AETMAC-co-EGDA), that not only helps to confine the soluble polysulfide species but also has the desired mechanical properties to allow stable cycling of high-sulfur loading cathodes. Through a combination of spectroscopic and electrochemical studies, we elucidate the chemical interactions that inhibit polysulfide shuttling. We also show that extensive cross-linkage enables this polymeric binder to exhibit a low degree of swelling as well as high tensile modulus and toughness. These attributes are essential to maintain the architectural integrity of the sulfur cathode during extended cycling. Using this material, Li–S cells with a high-sulfur loading (6.0 mg cm–2) and a low-intermediate electrolyte/sulfur ratio (7 μL:1 mg) achieve an areal capacity of 5.4 mA h cm−2and can be (dis)charged for 300 cycles with stable reversible redox behavior after the initial cycles.

Prediction of runout distance and deposit morphology is of great importance in hazard mitigation of geophysical flows, including viscoplastic mudflows. The major rheological parameters of mudflows, namely, yield stress and viscosity, are crucial factors in controlling the runout and deposition processes. However, the roles of the two parameters, especially in mudflows with high inertia, remain poorly understood and are not accounted for in runout scaling relations with source volume. Here we investigate the effects of flow rheology on runout scaling and deposit morphology using small‐scale laboratory experiments and three‐dimensional numerical simulations. We find that yield stress and viscosity both influence flow velocity gained during downslope propagation of mudflows, which is strongly correlated with the runout distance; the role of yield stress is more significant than viscosity. High yield stress and low viscosity lead to an elongated deposit, where longitudinal propagation is more significant than lateral spreading. In contrast, high viscosity promotes the dominance of lateral spreading of the deposit, while low yield stress and moderate viscosity produce an initial elongate deposit, followed by a secondary surge that spreads laterally near the head of the deposit. Following appropriate scaling relations for viscosity and yield stress, a general scaling function is proposed to incorporate flow properties in the well‐known correlation of runout distance and source volume. Our findings regarding the inertia effects and the roles of yield stress and viscosity enhance our understanding of mudflows, muddy debris flows, and other viscoplastic geophysical flows. Experiments and simulations reveal the role of inertia and rheology (yield stress and viscosity) in the runout behavior of rapid mudflowsDifferent combinations of rheological parameters are found to give rise to distinct deposit morphologyA generalized runout scaling relation is proposed incorporating rheological parameters

A comprehensive experimental and theoretical analysis of the isothermal transport of species for the two model ternary-electrolytes with LiTFSI-Li2S4/dioxolane (DOL)-dimethoxyethane (DME) and LiTFSI-Li2S6/DOL-DME formulations is presented. An unambiguous picture of the polysulfide’s mobility is set forth after a detailed investigation of the macroscopic transference number and diffusion coefficients. The new findings of incongruent diffusion for Li2S4species and high significance of cross-term diffusion coefficients reformulate a fledgling view of the prevalent redox-shuttle phenomena. The practical implications of this complex mechanism are discussed in detail.

There are fixed costs in production. One has to assemble rents earned in production lines to cover them. There are also fixed costs in consumption. Consumers assemble surpluses to cover them. In either case, rent assemblage could either be a quantity solution, a quality solution, or a combination of both. Once a fixed cost is committed by contract, it becomes historical. Yet compared to the option of paying this fixed cost all over again, increasing those quantities or qualities, which do not further increase this fixed cost, is less costly. The Law of Demand therefore implies the quality and/or the quantity solutions. The quality solution, as provided by the Alchian-Allen Theorem, is but a special case: where an increase in quality is the only viable solution under some specific real world constraints.

High-power (more than 500 mW) and high-speed (more than 1 Gbps) tapered lasers at 1060 nm are required in freespace optical communications and (at lower frequencies of around 100 MHz) display applications for frequency doubling to the green. On a 3 mm long tapered laser, we have obtained an open eye diagram at 1 Gbps, together with a high extinction ratio of 11 dB, an optical modulation amplitude of 530 mW, and a high modulation efficiency of 13 W/A. On a 4 mm-long tapered laser, we have obtained an open eye diagram at 700 Mbps, together with a high extinction ratio of 19 dB, a high optical modulation amplitude of 1.6 W, and a very high modulation efficiency of 19 W/A. On a 6 mm-long tapered laser, we have obtained a very high power of 5W CW and a very high static modulation efficiency of 59.8 W/A.

This study aimed to examine the participation of Australian Chinese in cardiovascular risk factor and cancer screening. A telephone survey of a random sample of Chinese in New South Wales, Australia, was conducted. The presence of, and participation in screening for, hypertension, hyperlipidaemia and diabetes were ascertained. Additionally, women were surveyed regarding breast cancer and cervical cancer screening. Five hundred and fifty-five subjects were interviewed. Generally, Australian Chinese were as likely to participate in health screening activities as the general population. However, Chinese with poor English-speaking ability were less likely to have had recent lipid testing (85.4% vs 91.2%, p=0.01) or mammography (63.2% vs 92.6%, p=0.01) than those who were proficient in English (adjusted for age and gender). Those not in employment were less likely to have had lipid testing (86.9% vs 88.4%, p=0.04), mammography (61.1% vs 93.5%, p=0.04) or Pap tests (64.7% vs 85.0%, p<0.01) than those in employment. Chinese who had been in Australia for less than 10 years were also less likely to undergo Pap tests (68.7% vs 79%, p=0.03). Overall, participation of Australian Chinese in health screening is within the community norm. However, those with poor English-speaking skills, who are not employed, or who had been resident in Australia for a shorter duration are less likely to undergo some of these health activities. Health promotion efforts need to be directed at disadvantaged subgroups of Chinese Australians.

In the present paper, effects of through-the-thickness stitching of delaminated glass/epoxy composite laminates with two different types of aramid threads, Kevlar® and Twaron® threads, on the buckling loads are studied. The buckling loads are predicted based on the Southwell, Vertical displacement and Membrane strain plot methods from the experimental data. Flexural modulus of the stitched and unstitched glass/epoxy composite laminates, knot tensile strength of Kevlar® and Twaron® stitching threads are obtained experimentally. From the Southwell, Vertical displacement and Membrane strain plot methods it is observed that stitching either by Kevlar® or Twaron® threads is effective in improving the buckling strength of glass/epoxy composite laminates when the delamination length is greater than 0.5L, L is the length of the laminate.

Sputtering conditions to produce nearly equiatomic NiTi films were studied. Two heat treatment methods, substrate heating (550 °C) and post-sputter heat treatments (solution heat treatment at 700 °C and precipitation heat treatment at 400 °C), were used to crystallize NiTi films. The NiTi films were analysed for their atomic composition, crystal structure, transformation temperatures, residual stress and Young's modulus. NiTi films produced by rf magnetron sputtering were slightly titanium rich. With appropriate post-sputter heat treatment, NiTi films with phase transformation temperatures within the human body temperature range (34-42 °C) were produced. The films also demonstrated two-way shape memory training capability.

Radiation dose deposited on a radiochromic film is considered as a dose image. A precise image extraction system with commensurate capabilities is required to measure the transmittance of the image and translate it to radiation dose. This paper describes the development of a spectral microdensitometer which has been designed to achieve this goal under the conditions of (a) the linearity and sensitivity of the dose response curve of the radiochromic film being highly dependent on the wavelength of the analysing light, and (b) the inherent high spatial resolution of the film. The microdensitometer consists of a monochromator which provides an analysing light of variable wavelength, a film tray on a high-precision scanning stage, a transmission microscope coupled to a thermoelectrically cooled CCD camera, a microcomputer and corresponding interfaces. The measurement of the transmittance of the radiochromic film is made at the two absorption peaks with maximum sensitivities. The high spatial resolution of the instrument, of the order of micrometres, is achieved through the use of the microscope combined with a measure-and-step technique to cover the whole film. The performance of the instrument in regard to the positional accuracy, system reproducibility and dual-peak film calibration was evaluated. The results show that the instrument fulfils the design objective of providing a precise image extraction system for radiochromic films with micrometre spatial resolution and sensitive dose response.

Breast cancer is a rapidly increasing problem in many developing countries, and cytotoxic chemotherapy is now an integral part of its management. In several developing countries, the carriage of hepatitis B virus (HBV) in cancer patients may be as high as 12%, and such patients are at risk of developing fatal HBV reactivation during chemotherapy. HBV reactivation is well recognized in patients with hematological malignancies, but limited data are available on patients with other, more common, cancers, such as breast cancer. Recent data have suggested that increased viral replication, an indication of HBV reactivation, may precede clinical hepatitis. In the absence of serial HBV DNA monitoring, HBV reactivation during chemotherapy may have been underestimated. In this prospective study, breast cancer patients who were hepatitis B surface antigen (HBsAg) seropositive were followed up during chemotherapy. The main objectives were to determine the incidence of HBV reactivation in breast cancer patients undergoing conventional chemotherapy; to investigate whether “serial HBV DNA monitoring” improves the accuracy of diagnosing HBV reactivation when compared with previous schema that only measured HBV DNA at the time of clinical hepatitis (“conventional monitoring”); and to assess the clinical consequences as a result of developing the condition. The secondary objective was to identify risk factors associated with this condition. Over an 18‐month period, 41 patients were studied. Ten developed HBV reactivation by conventional monitoring criteria, but with serial HBV DNA monitoring, seven additional patients were diagnosed when increased HBV DNA levels were detected before, but not concomitant with, clinical hepatitis. Thus, a total of 17 patients (41%) developed HBV reactivation. Premature termination of chemotherapy or delay in treatment schedules occurred in 71% of the patients who developed viral reactivation, as compared with 33% in those who did not develop the condition (P= 0.019). No risk factors associated with the development of HBV reactivation could be identified. Serial monitoring of HBV DNA, in addition to liver function, increases the sensitivity of diagnosing of HBV reactivation, and helps explain some cases that would otherwise be labeled as “cryptogenic hepatitis,” for which concomitant HBV DNA measured at the time of hepatitis was undetectable. The present study highlights the importance of monitoring HBsAg‐seropositive patients who are receiving chemotherapy for common solid tumors such as breast cancer. J. Med. Virol. 70:553–561, 2003. © 2003 Wiley‐Liss, Inc.

Highly luminescent distyrylstilbenes (DSBs) bearing either propoxy or oxadiazole-surface-functionalized poly(benzyl ether)-type dendritic wedges at one end have been synthesized by a stepwise Wadsworth−Emmon reaction. We show for the first time that an emissive core bearing asymmetrically substituted surface-functionalized dendrons exhibits more favorable luminescence properties than the symmetrically dendron-substituted core. All of these asymmetrically dendron-substituted DSBs display very similar optical characteristics in both solution and solid state, except for a few nanometers of blue shift in the absorption and emission maxima as compared to the corresponding symmetrically dendron-substituted DSBs. Their solution fluorescence lifetimes and photoluminescence quantum efficiencies were found to be smaller than those of the symmetrically dendron-substituted counterparts, which was attributed to the inefficient shielding of the surface-functionalized dendritic wedges of the asymmetrically dendron-substituted DSBs. However, the energy transfer efficiency of the oxadiazole-surface-functionalized G1-dendron-substituted DSB, 2, reaches 75%, which is the highest among all of the dendritic DSBs synthesized so far. Single-layer light-emitting diodes (LEDs) using dendritic DSB doped poly(N-vinylcarbazole) (PVK) film as an emissive layer with a structure of (ITO/DSB:PVK/Al) have been fabricated and investigated. Importantly, LEDs based on these asymmetrically dendron-substituted DSBs exhibit better device performance than do LEDs based on the corresponding symmetrically dendron-substituted counterparts. Furthermore, there is a remarkable enhancement in device performance, particularly for oxadiazole-surface-functionalized asymmetrically dendron-substituted DSB-based LEDs, when the emissive layer is blended with diphenylamine.

A novel series of poly(benzyl ether) type dendritic distyrylbenzenes bearing various electron or hole affinitive moieties including 1,3,4-oxadiazole, cyano, and propoxy groups on the outer surface of the first- and second-generations dendritic wedges have been synthesized for blue-light emission. Both theoretical and optical studies show that incorporation of the surface functionalized dendritic wedges into the nonconjugated meta positions of a distyrylstilbene skeleton does not disrupt the coplanarity of the π-conjugated core. Excitation of the surface functionalized dendritic wedges leads to substantial energy transfer from the dendritic wedges to the emissive core (up to 59%). Importantly, all the dendritic distyrylstilbenes show very high fluorescence quantum yields (over 93%). Single-layer light-emitting diodes (LED) using dendritic distyrylstilbene (DSB) doped poly(N-vinylcarbazole) (PVK) film as an emissive layer with structure of (ITO/DSB:PVK/Al) have been fabricated and investigated. The emission wavelengths and spectral features are very similar among the solution emission, solid-state photoluminescence, and electroluminescence spectra. The device performance of the first-generation dendritic DSB doped single-layer LEDs is generally superior to that of the corresponding second-generation dendrimer based devices. In addition, the propoxy surface functionalized dendritic DSB devices consistently show the best device performance and relative stability among the others.

Although conventional screen–film mammography has excellent spatial resolution and is commonly used as a screening tool, certain inherent limitations prevent its further improvement. New digital mammography techniques, despite lower spatial resolution than screen–film mammography, may overcome these limitations. This study compared lesion detectability between charge coupled device-based digital spot mammography and conventional spot mammography. A total of 100 sets of images of specially designed breast phantoms was acquired, with variable background achieved by overlapping several layers of grapefruit fibre on a 4 cm thick lucite slab, using both modalities. 75 sets were “normal” images and 25 sets were images with simulated lesions. Four radiologists assessed the images according to a five-point confidence scale. The results were used to construct receiver operating characteristic curves. No statistical difference was observed between the two sets of curves for individual radiologists as well as pooled data. The lower spatial resolution of digital mammography was compensated for by its higher contrast sensitivity relative to conventional spot mammography.

A simple, one-step procedure for generating ordered, crystalline methylene chains on polymeric surfaces via urethane linkages was developed. The reaction of dodecyl isocyanate with surface hydroxyl functional groups, catalyzed by dibutyltin dilaurate, formed a predominantly all-trans, crystalline structure on a cross-linked poly(2-hydroxyethyl methacrylate) (pHEMA) substrate. Allophanate side-branching reactions were not observed. Both X-ray photoelectron spectrocopy and time-of-flight secondary ion mass spectrometry show that the surface reaction reached saturation after 30 min at 60 °C. Unpolarized Fourier transform infrared-attenuated total reflection showed that, after 30 min, the stretching frequencies, νCH2,asym and νCH2,sym, decreased and approached 2920 and 2850 cm^-1, indicative of a crystalline phase. The distance between two hydroxyl groups is roughly 4 Å. A tilt angle of 33.5° ± 2.4° was estimated by dichroic ratios measured in polarized ATR according to the two-phase and Harrick thin film approximations. The findings reported here are significant in that the possibilities for using structures similar to self-assembled monolayers (SAMs) are expanded beyond the rigid gold and silicon surfaces used through most of the literature. Thus, SAMs, biomimetics for ordered lipid cell wall structures, can be applied to real-world biomedical polymers to modify biological interactions. The terminal groups of the SAM-like structure can be further functionalized with biomolecules or antibodies to develop surface-based diagnostics, biosensors, or biomaterials.

Abstract: We report cerebral SPECT studies on two siblings with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS). Tc-99m HMPAO brain SPECT was performed 8, 19 and 30 days after a stroke-like episode in one case and 10 days after a stroke-like episode, 6 h after a partial seizure and as a follow-up study in the other. Increased blood flow was seen in both these patients with stroke-like episodes due to MELAS. The cause of the increased blood flow is uncertain, but it may be related to the decreased pH created by local increase in lactic acid.

Hepatitis B virus (HBV) reactivation has been described in cancer patients who received cytotoxic/immunosuppressive therapy and may result in liver damage of varying degrees of severity. There is no known effective treatment. Lamivudine, a nucleoside analogue, has been found to suppress HBV replication and to improve histology in chronic carriers of hepatitis B virus. The outcome of lamivudine therapy (at doses of 100 or 150 mg/day) in eight patients who developed HBV reactivation while receiving cytotoxic chemotherapy is described. Each of the eight patients had >98% suppression of the pretreatment HBV DNA levels. Three of the five patients who were initially HBeAg positive underwent seroconversion. Five patients had normalization of liver function tests and improvement in clinical condition. However, one patient died of hepatic failure due to HBV‐related submassive liver necrosis, and two died of widespread metastases (including liver) from the primary malignancies. It is concluded that early commencement, i.e., at the onset of HBV reactivation before severe hepatic decompensation, of lamivudine may be effective in the control of HBV reactivation during chemotherapy. In Hong Kong, where hepatitis B infection is endemic, we propose to screen all cancer patients for hepatitis B surface antigen before immunosuppressive/cytotoxic therapy, and to closely monitor liver function of those who are found to be HBsAg seropositive. J. Med. Virol. 59:263–269, 1999. © 1999 Wiley‐Liss, Inc.