Transient quantum evolution of 2D electrons under photoexcitation of a deep center

We have considered the ballistic propagation of the 2D electron Wigner distribution, which is excited by an ultrashort optical pulse from a short-range impurity into the first quantized subband of a selectively-doped heterostructure with high mobility. Transient ionization of a deep local state into a continuum conduction c-band state is described. Since the quantum nature of the photoexcitation, the Wigner distribution over 2D plane appears to be an alternating-sign function. Due to a negative contribution to the Wigner function, the mean values (concentration, energy, and flow) demonstrate an oscillating transient evolution in contrast to the diffusive classical regime of propagation.Comment: 8 pages, 6 figures, pape

Quantifying the Value of CCS for the Future Electricity System

Many studies have quantified the cost of Carbon Capture and Storage (CCS) power plants, but relatively few discuss or appreciate the unique value this technology provides to the electricity system. CCS is routinely identified as a key factor in least-cost transitions to a low-carbon electricity system in 2050, one with significant value by providing dispatchable and low-carbon electricity. This paper investigates production, demand and stability characteristics of the current and future electricity system. We analyse the Carbon Intensity (CI) of electricity systems composed of unabated thermal (coal and gas), abated (CCS), and wind power plants for different levels of wind availability with a view to quantifying the value to the system of different generation mixes. As a thought experiment we consider the supply side of a UK-sized electricity system and compare the effect of combining wind and CCS capacity with unabated thermal power plants. The resulting capacity mix, system cost and CI are used to highlight the importance of differentiating between intermittent and firm low-carbon power generators. We observe that, in the absence of energy storage or demand side management, the deployment of intermittent renewable capacity cannot significantly displace unabated thermal power, and consequently can achieve only moderate reductions in overall CI. A system deploying sufficient wind capacity to meet peak demand can reduce CI from 0.78 tCO2 /MWh, a level according to unabated fossil power generation, to 0.38 tCO2 /MWh. The deployment of CCS power plants displaces unabated thermal plants, and whilst it is more costly than unabated thermal plus wind, this system can achieve an overall CI of 0.1 tCO2 /MWh. The need to evaluate CCS using a systemic perspective in order to appreciate its unique value is a core conclusion of this study

Power Capacity Expansion Planning Considering Endogenous Technology Cost Learning

We present an power systems optimisation model for national-scale power supply capacity expansion considering endogenous technology cost reduction (ESO-XEL). The mixed-integer linear program minimises total system cost while complying with operational constraints, carbon emission targets, and ancillary service requirements. A data clustering technique and the relaxation of integer scheduling constraints is evaluated and applied to decrease the model solution time. Two cost learning curves for the different power technologies are derived: one assuming local learning effects, the other accounting for global knowledge spill-over. A piece-wise linear formulation allows the integration of the exponential learning curves into the ESO-XEL model. The model is applied to the UK power system in the time frame of 2015 to 2050. The consideration of cost learning effects moves optimal investment timings to earlier planning years and influences the competitiveness of technologies. In addition, the maximum capacity build rate parameter influences the share of power generation significantly; the possibility of rapid capacity build-up is more important for total system cost reduction by 2050 than accounting for technology cost reduction

An MILP modeling approach to systemic energy technology valuation in the 21st Century energy system

New cannot be measured with old. The transformation of the electricity system from a network of fossil-based dispatchable power plants to one with large amounts of intermittent renewable power generation, flexible loads and markets, requires a concurrent development of new evaluation tools and metrics. The focus of this research is to investigate the value of power technologies in order to support decision making on optimal power system design and operation. Technology valuation metrics need to consider the complexity and interdependency of environmental and security objectives, rather than focusing on individual cost-competitiveness of technologies outside of the power system. We present the System Value as a new technology valuation metric, based on a mixed-integer linear program (MILP) formulation of a national-scale electricity system. The Electricity System Optimization model is able to capture detailed technical operation of the individual power plants as well as environmental and security requirements on the system level. We present a case study on the System Value of onshore wind power plants in comparison with Carbon Capture and Storage (CCS) equipped gas-fired power plants in a 2035 UK electricity system. Under the given emission constraints, the deployment of both technologies reduce total system cost of electricity generation. In the case of CCS-equipped power plants the reductions in total system cost are 2 to 5 times higher than for the deployment of onshore wind capacity

Association of Epstein Barr Virus (EBV) with nasopharyngeal carcinoma (NPC)

Aim: To observe the frequency of nasopharyngeal carcinoma (NPC) and its association with Epstein Barr Virus (EBV) infection. Setting: This study included consecutive cases of nasopharyngeal carcinoma, which were diagnosed in the Department of Pathology at the Aga Khan University Hospital, Karachi in the period of two years (1996-97). Methods: These tumors were initially evaluated on H&E stained sections. The tumors showing evidence of keratinization were excluded from the study. The Epstein Barr Virus was detected with the help of Polymerase chain reaction in formalin fixed, paraffin embedded tissue sections. Results: During the study period, seventeen cases of nasopharyngeal carcinoma were diagnosed which comprised 0.3% of all malignant tumors. The age ranged from 5 years to 70 years with male to female ratio of 2.4:1. The NPC was more prevalent in adults (71%) as compared to children (29%) under 15 years. Six cases (35%) exhibited positive signal for Epstein Barr Virus. Conclusion: Nasopharyngeal carcinoma is an infrequent tumor. The prevalence of Epstein Barr virus infection in nasopharyngeal carcinoma is quite low as compared to other regions of the world

Morphological pattern and frequency of thyroid tumors

Objective: The present study was done to evaluate the frequency of thyroid cancer and to find out the prevalence of histological types of thyroid tumor with respect to age and sex group.Setting: This study included consecutive cases of malignant tumors of thyroid gland, which were diagnosed in the Department of Pathology at the Aga Khan University Hospital, Karachi during the period of three years (1995-1997).Methods: These cases were evaluated on H & E stained sections from paraffin embedded 10% buffered formalin fixed tissue blocks. Special stains and immunohistochemical analysis were performed whenever required.Results: A total of 8541 malignant tumors were diagnosed in a period of 3 years which included 103 (1.2%) cases of thyroid cancer. Thyroid tumors were more prevalent in females with female to male ratio of 2.6:1. Papillary carcinoma (69%) was the most common histological type of thyroid tumors, followed by follicular carcinoma (11.6%), medullary carcinoma (9.7%), anaplastic carcinoma (5.9%), non-Hodgkin\u27s lymphoma (2.9%) and unclassified tumors (0.9%) in order of frequency.Conclusion: Thyroid cancer was more common in females. Papillary carcinoma was the most common histological type of thyroid tumors in females as well as in males. Papillary carcinoma was more prevalent in third, fourth and fifth decades of life while follicular and anaplastic carcinomas were more frequent after the fourth decade of life

Removal of basic green 5 by carbonaceous adsorbent: Adsorption kinetics

The Eucalyptus lenceolata wood was collected from Malakand division, Khyber Pakhtunkhwa Pakistan. Chemical activation of sample was conducted for surface efficiency. Batch studies were performed to address various experimental parameters like, contact time, temperature and adsorbent dosage for the removal of dye. For elemental analysis, surface morphology and for identification of different functional groups, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) techniques were applied, respectively. Removal of dye (Basic Green 5) was studied on raw and activated samples by kinetics adsorption at different temperature. BET adsorption isotherm was used to characterize the surface area of the sample. Under the conditions investigated, a higher carbonization temperature promoted development of porous structures. Intraparticle diffusion, Elovich and Bhangam models were used for adsorption kinetics studies. From adsorption kinetic data thermodynamic parameters like ΔH≠, ΔS≠ and ΔE≠ were determined. The results show that the adsorption is spontaneous process. The endothermic nature of adsorptive process is due to the positive value of enthalpy. The negative entropy shows that acids molecules on the surface of adsorbent take an oriented position. The results shows that all the models were best fitted for these data of adsorption.               KEY WORDS: Activated carbon, Adsorption, SEM, EDS, FTIR, Surface area Bull. Chem. Soc. Ethiop. 2017, 31(3), 411-422. DOI: http://dx.doi.org/10.4314/bcse.v31i3.

Efficacy of Various IPM Modules on Biotic Pressure and Green Forage Yield in a Forage Production System (Cowpea + BN Hybrid – Berseem mixed with Mustard + BN Hybrid)

Various control measures by themselves are not free from one or the other limitations to provide safe, economically viable and efficient in pest population suppression. The economics is much more relevant when we talk of low value commodity like forage crops. Viewing this multifaceted problem and inherent limitations of each control method the ultimate solution lies in integrated pest control expedient. The connotation of the approach is to utilize all the possible methods of control including maximum exploitation of naturally existing populations and regulating factors in as compatible manner as possible to keep the pest population levels below economic threshold. Earlier, IPM in fodder crops has been worked out by Shri Ram and Gupta, 1989; Pandey et al., 2000; Shah et al., 2011