The low absorption of cyclopentadienyl-Fe-cumene hexafluorophosphate (I-261) above 300 nm limits its utilization of longer wavelength emission from light sources. We report here the synthesis and photoactivity of a carbazole-bound ferrocenium salt, cyclopentadienyl-Fe-carbazole hexafluorophosphate ([Cp-Fe-carbazole] + PF 6 − ), which efficiently absorbs radiation between 300 and 400 nm. Its photoactivity is higher than that of I-261 as a cationic photoinitiator. When the photosensitizer benzoyl peroxide (BPO) is employed, [Cp-Fe-carbazole] + PF 6 − can obviously be sensitized. Two other ferrocenium salts with amine groups, cyclopentadienyl-Fe-aniline hexafluorophosphate ([Cp-Fe-aniline] + PF 6 − ) and cyclopentadienyl-Fe-p-methylaniline hexafluorophosphate ([Cp-Fe-p-methylaniline] + PF 6 − ) were also studied. As photoinitiators, they perform poorly and can not be sensitized by BPO.
The decomposition of apple (Malus domestica) leaf litters has a pivotal role in nutrient release in orchard ecosystems. We studied the decomposition rate and subsequent release of nitrogen (N), phosphorus (P), and potassium (K) nutrients over 24-months using the litterbags method, from three types of litters sampled from an apple orchard which received different rates of N, P, K fertilization (control, CK; low fertilizer rate, LF; high fertilizer rate, HF). The patterns of mass loss of all three litters were quite similar following the exponential decay model. However, the amount of mass loss was greater for HF and LF litters than that for CK litter over the first six months. During the initial six months, concentrations of N and P in the leaf litters increased while that of K declined. Subsequently, concentrations of all elements decreased during 24-months of incubation. The release of N and P from leaf litter was positively correlated to the respective concentrations in the leaf litter at the beginning of decomposition. The amounts of N and P release from the litter were greater for that collected from the trees which received HF than that under CK and LF treatments during the course of decomposition in the two years. The rapid release of K occurred during the early stage across all litters and was not influenced by varying levels of leaf nutritional status. At the end of 24 months of decomposition, the relative release of nutrients from litters followed the order: K > N > P. The mean quantities of N, P, and K released during the first and second year following the application of 10, 6, 58% and 63, 6, 8% of recommended rates at respective nutrients for young apple orchards in Loess Plateau. Therefore, the results suggest that nutrient release from leaf litter in an apple orchard system can contribute a significant portion of the nutrient requirement for apple production. Accounting for this nutrient contribution in the annual fertilizer management is important to avoid excess application, optimize net returns, and maintain sustainable production systems.
Heterogeneous cellular Network (HetNet) has emerged as a promising technology for the 5th generation mobile networks (5G) that can be used to meet the high demand of data rate and better quality of service (QoS) performance. However, the performance of HetNet will depend on how scarce resources such as frequency, time, power and spatial resource are shared among user equipments (UEs) in the system and also how interference is controlled. In this work, we utilize UE-centric clustering as a tool to effectively determine the interfering BSs that cause significant interference to each UE in the network. These interfering BSs together with the serving BSs of these interfered UEs will coordinate and make resource allocation decision together to allocate spatial directions to each UE in the network in order to manage interference in the network. We formulate the resource allocation problem as maximizing the weighted sum-rate of HetNet while fulfilling some power, QoS and interference constraints. This optimization problem is non-convex. We readily split the RA problem into two sub-problems: the spatial direction allocation problem and the power allocation problem respectively. We are able to solve these problems efficiently using SeDumi, which provides a general purpose implementation of interior point methods. Simulation results of our proposed method, when compared with the other existing methods, show significant improvement.
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