Atmospheric teleconnection mechanisms of extratropical North Atlantic SST influence on Sahel rainfall

Extratropical North Atlantic cooling has been tied to droughts over the Sahel in both paleoclimate observations and modeling studies. This study, which uses an atmospheric general circulation model (GCM) coupled to a slab ocean model that simulates this connection, explores the hypothesis that the extratropical North Atlantic cooling causes the Sahel droughts via an atmospheric teleconnection mediated by tropospheric cooling. The drying is also produced in a regional climate model simulation of the Sahel when reductions in air temperature (and associated geopotential height and humidity changes) from the GCM simulation are imposed as the lateral boundary conditions. This latter simulation explicitly demonstrates the central role of tropospheric cooling in mediating the atmospheric teleconnection from extratropical North Atlantic cooling. Diagnostic analyses are applied to the GCM simulation to infer teleconnection mechanisms. An analysis of top of atmosphere radiative flux changes diagnosed with a radiative kernel technique shows that extratropical North Atlantic cooling is augmented by a positive low cloud feedback and advected downstream, cooling Europe and North Africa. The cooling over North Africa is further amplified by a reduced greenhouse effect from decreased atmospheric specific humidity. A moisture budget analysis shows that the direct moisture effect and monsoon weakening, both tied to the ambient cooling and resulting circulation changes, and feedbacks by vertical circulation and evaporation augment the rainfall reduction. Cooling over the Tropical North Atlantic in response to the prescribed extratropical cooling also augments the Sahel drying. Taken together, they suggest a thermodynamic pathway for the teleconnection. The teleconnection may also be applicable to understanding the North Atlantic influence on Sahel rainfall over the twentieth century

Thermodynamic analysis of a novel fossil-fuel–free energy storage system with a trans-critical carbon dioxide cycle and heat pump

This paper presents and analyzes a novel fossil-fuel–free trans-critical energy storage system that uses CO2 as the working fluid in a closed loop shuttled between two saline aquifers or caverns at different depths: one a low-pressure reservoir and the other a high-pressure reservoir. Thermal energy storage and a heat pump are adopted to eliminate the need for external natural gas for heating the CO2 entering the energy recovery turbines. We carefully analyze the energy storage and recovery processes to reveal the actual efficiency of the system. We also highlight thermodynamic and sensitivity analyses of the performance of this fossil-fuel–free trans-critical energy storage system based on a steady-state mathematical method. It is found that the fossil-fuel–free trans-critical CO2 energy storage system has good comprehensive thermodynamic performance. The exergy efficiency, round-trip efficiency, and energy storage efficiency are 67.89%, 66%, and 58.41%, and the energy generated of per unit storage volume is 2.12 kW·h/m3, and the main contribution to exergy destruction is the turbine reheater, from which we can quantify how performance can be improved. Moreover, with a higher energy storage and recovery pressure and lower pressure in the low-pressure reservoir, this novel system shows promising performance

Opinion Mining on Non-English Short Text

As the type and the number of such venues increase, automated analysis of sentiment on textual resources has become an essential data mining task. In this paper, we investigate the problem of mining opinions on the collection of informal short texts. Both positive and negative sentiment strength of texts are detected. We focus on a non-English language that has few resources for text mining. This approach would help enhance the sentiment analysis in languages where a list of opinionated words does not exist. We propose a new method projects the text into dense and low dimensional feature vectors according to the sentiment strength of the words. We detect the mixture of positive and negative sentiments on a multi-variant scale. Empirical evaluation of the proposed framework on Turkish tweets shows that our approach gets good results for opinion mining

Potential core lengths of round jets in stagnant and moving environments

This paper investigates the change of velocity and concentration fields in the initial region of a round jet in stagnant fluid and in a moving environment of the co-flow, counter-flow or cross-flow situation. The aim was to discuss issues of flow establishment and in the initial region, to determine the potential core length, and to observe the effect of a moving ambient. Turbulent jet velocities and concentration were measured with the planar imaging techniques of particle-image velocimetry (PIV) and laser-induced fluorescence (LIF). The mean flow fields were obtained and analyzed to investigate the validity of 1/. x decay relationship for jet centerline velocity and concentration. Values for the decay constant and jet virtual origin were obtained from the data. While the results show that the decay constant is increased by a co-flow but reduced by a counter-flow or a cross-flow, the virtual origin was found to be affected as well. The overall effect is that any situation of the moving environment leads to a slight reduction of the physical length of the potential core. The paper also suggests an intermittency function for the analysis of fluctuating jet concentration field in the potential core. The mean intermittency function provides a direct and reliable estimate of the potential core length of a jet in a moving environment. © 2011 International Association of Hydro-environment Engineering and Research, Asia Pacific Division.postprin

Outcome for Hong Kong residents undergoing cadaveric liver transplantation in mainland China

Objective. To review the outcome for Hong Kong residents undergoing cadaveric liver transplantation in mainland China. Design. Retrospective study. Setting. Liver Transplant Centre, university teaching hospital, Hong Kong. Subjects and methods. A retrospective review of medical records was undertaken for patients at Queen Mary Hospital who underwent cadaveric liver transplantation in China between 1 January 1997 and 31 December 2001. Results. Fifteen patients from Queen Mary Hospital underwent cadaveric liver transplantation in China during the study period. Eleven were men and four were women. Their mean age was 51 years. Disease indications included hepatitis B-related liver cirrhosis (n=7), hepatitis B-related liver cirrhosis with hepatocellular carcinoma (n=5), hepatitis C-related liver cirrhosis (n=1), hepatitis C-related liver cirrhosis with hepatocellular carcinoma (n=1), and polycystic liver and kidney disease (n=1). Nine patients were already waiting for liver transplantation at Queen Mary Hospital, and two of the nine patients were on the 'urgent' list. The overall survival rate was 80.0% at 6 months and 73.3% at 12 months. There were four (27%) deaths, two of which occurred in China. Of the 11 surviving patients, nine (82%) developed complications. Nineteen complications were seen in the 13 patients who were managed in Hong Kong following their return from China. Infective and biliary complications accounted for 58% and 26% of complications, respectively. Major complications necessitated prolonged hospitalisation for four patients and two required further laparotomy. Conclusion. Although cadaveric liver transplantation in China is an option for Hong Kong residents, patients and clinicians should be aware of the possible outcomes and resource implications.published_or_final_versio

Background independent action for double field theory

Double field theory describes a massless subsector of closed string theory with both momentum and winding excitations. The gauge algebra is governed by the Courant bracket in certain subsectors of this double field theory. We construct the associated nonlinear background-independent action that is T-duality invariant and realizes the Courant gauge algebra. The action is the sum of a standard action for gravity, antisymmetric tensor, and dilaton fields written with ordinary derivatives, a similar action for dual fields with dual derivatives, and a mixed term that is needed for gauge invariance.Comment: 45 pages, v2: minor corrections, refs. added, to appear in JHE

Radio variability of 1st 3-months Fermi blazars at 5 GHz: affected by interstellar scintillation?

Blazars from the first-three-months Fermi-AGN list were observed with the Urumqi 25m radio telescope at 5GHz in IDV (Intra-Day Variability) mode and inter-month observation mode. A significant correlation between the flux density at 5GHz and the gamma-ray intensity for the Fermi-LAT detected blazars is seen. There is a higher IDV detection rate in Fermi detected blazars than those reported for other samples. Stronger variability appears at lower Galactic latitudes; IDV appears to be stronger in weaker sources, indicating that the variability is affected by interstellar scintillation.Comment: 4 pages, 4 figures, in proceedings of 'Multiwavelength Variability of Blazars' in Guangzhou Uni. of China, 22-24, Sep. 2010, to appear in JA

Estimation of paleo-firing temperatures using luminescence signals for the volcanic lava baked layer in Datong, China

Eight paleo-fired samples from the baked layer in different depths under the lava and one unfired sample were collected from Datong, China. Fine quartz grains (4–11 μm) from samples were used for probing into relationship between luminescence signals and paleo-firing temperatures. Findings from the re-firing experiments indicated that using thermoluminescence (TL) and optically stimulated luminescence (OSL) sensitivity changes could estimate the paleo-firing temperatures of samples: (1) 110 °C TL sensitivity change rate against the re-firing temperature can tell whether the sample has been fired to temperatures above 500 °C or not; (2) 150 °C TL sensitivity against the re-firing temperature can indicate whether the sample has been fired to temperatures above 900 °C or not; (3) the more specific paleo-firing temperatures can be estimated by comparing the ratio of OSL and 150 °C TL sensitivities against re-firing temperatures. Results showed that the paleo-firing temperatures of the eight lava-baked samples decreased exponentially with the distance from the lava. Based on the estimated temperature profile, the temperature of the lava was estimated to be about 1100 °C.postprin

Luminescence dating of volcanic eruptions in Datong, northern China

In this study, fine-grain quartz was used for luminescence dating for lava baked samples from different sites in Datong. Optical stimulated luminescence (OSL), thermal transferred OSL (TT-OSL)/recuperated OSL (Re-OSL) and thermoluminescence (TL) dating protocols were applied. For these samples, the OSL signals saturate at about 300–400 Gy, which limits their age to less than 100 ka based on their ambient dose rates. The TT-OSL/Re-OSL method has poor dose recovery. TL dating gives reliable results, and multiple-aliquot regenerative-dose TL method with sensitivity change correction based on the 325 °C TL peak of a test dose can be applied for samples up to 400 ka. The results indicate that the ages of the volcanoes in Datong are from 380 ka to 84 ka. The volcanic activity started earlier in the southeast area than those in the northwest part, which is consist with the literature data.postprin

The Reliability of Histamine Pharmacodynamic Response Phenotype Classification in Children With Allergic Disease.

We have identified distinct histamine pharmacodynamic response phenotypes in children with allergic disease utilizing histamine iontophoresis with laser Doppler (HILD). These response phenotypes may be relevant in guiding therapeutic decision making for agents targeting the allergic response pathways. However, the reliability of these response phenotypes has not been assessed. Therefore, we performed HILD in children with allergic rhinitis and/or asthma on two to three separate occasions. HILD response-time data were analyzed in NONMEM using a linked effect PKPD model. Examination of observed vs. classified response phenotypes predicted response plots and the sum of residuals. The intraclass correlation coefficient (ICC) was used to determine the reliability of phenotype classification. Eighty-two percent of children exhibited a reliable histamine response phenotype [intraclass correlation coefficient 0.77 (95% CI 0.44–0.93]. These preliminary results suggest moderate reliability of HILD response phenotype in children. Further exploration is needed to determine contributions to phenotype variability