Associated production of the top-pions and single top at hadron colliders

In the context of topcolor assisted technicolor(TC2) models, we study the production of the top-pions $\pi_{t}^{0,\pm}$ with single top quark via the processes $p\bar{p} \to t\pi_{t}^{0}+X$ and $p\bar{p} \to t\pi_{t}^{\pm}+X$, and discuss the possibility of detecting these new particles at Tevatron and LHC. We find that it is very difficult to observe the signals of these particles via these processes at Tevatron, while the neutral and charged top-pions $\pi_{t}^{0}$ and $\pi_{t}^{\pm}$ can be detecting via considering the same sign top pair $tt\bar{c}$ event and the $tt\bar{b}$ (or $t\bar{t}b$) event at LHC, respectively.Comment: latex files,14 pages, 7 figures. Accepted for publication in Phys. Rev.

Investigation of vapor injection heat pump system with a flash tank utilizing R410A and low-GWP refrigerant R32

Vapor injection technique has proven to be effective in improving heat pump system performance, especially for cooling application at high ambient and heating application at low ambient temperature conditions. Recent research on vapor injection technique has been mostly focused on the internal heat exchanger cycle and flash tank cycle. The flash tank cycle typically shows better performance than the internal heat exchanger cycle. However, the flash tank cycle control strategy is not yet clearly defined. Improper system control strategy would result in undesirable amount of liquid refrigerant injected to the compressor or poor system performance. In this research work, a novel cycle control strategy for a residential R-410A vapor injection flash tank heat pump system was developed and experimentally investigated. The proposed cycle control strategy utilizes an electronic expansion valve (EEV) coupled with a proportional-integral-derivative (PID) controller for the upper-stage expansion and a thermostatic expansion valve (TXV) for the lower-stage expansion, and applies a small electric heater in the vapor injection line to introduce superheat to the injected vapor thus providing a control signal to the upper-stage EEV. The proposed control strategy functions effectively for both transient and steady-state operating conditions. As global warming has raised more critical concerns in recent years, refrigerants with high global warming potentials (GWP) are facing the challenges of being phased out. R410A, with a GWP of 2,088, has been widely used in residential air-conditioners and heat pump systems. A potential substitute for R410A is R32, which has a GWP of 675. This research work also investigates the performance difference using R410A and R32 in a vapor-injected heat pump system. A drop-in test was performed using R32 in a heat pump system that is designed to utilize R410A, for both cooling and heating conditions. Through experimentation, it was found that there was improvement for capacity and coefficient of performance (COP) using R32, as compared to an identical cycle using R410A. The compressor, heat exchangers and two-stage vapor injection cycle have been modeled and validated against experimental data to facilitate an optimization study. Heat exchangers were optimized using 5 mm copper tubes and result in significant cost reduction while maintaining the same capacity. Compressor cooling was investigated to decrease the high compressor discharge temperature for R32

Strategies for recombinant protein production in maize

Maize is not only one of the world\u27s most important crops, but it is also the first field-grown plant-based recombinant expression system developed for commercial purposes. With advantages of low cost, high yield, high protein stability, and well-developed transformation technology over other plant systems, maize is considered to be an ideal recombinant production system. However, there are three major challenges limiting the use of maize for producing recombinant proteins: 1) maize lacks mammalian-like post-translational modification ability that may be required for pharmaceutical and industrial proteins; 2) transgenic pollen containment in open-field production; and 3) low expression of recombinant products. The aim of the present study was to develop strategies to safely produce recombinant proteins with high yield and adequate modification in maize seeds. Firstly, we showed that the recombinant human collagen type I alpha 1 (rCIα1) with high ratio of hydroxylated prolines (Hyp) similar to native human collagen was expressed in maize seeds co-expressing a recombinant human prolyl 4-hydroxylase (rP4H). The hydroxylated rCIα1 had a markedly enhanced thermal stability compared to non-hydroxylated rCIα1. Secondly, we demonstrated that a cytoplasmic male-sterile maize system could be used for open-field production of maize-derived recombinant protein to minimize contamination risk caused by pollen drift. Two strategies were presented: the transgene was directly transformed into a male-sterile line via biolistic- or Agrobacterium -mediated methods, or introgressed from male-fertile to male-sterile germplasm by conventional breeding. The male-sterile transgenic maize seed from the second strategy can be used for open-field production by using a non-transgenic maize pollen donor to produce 100% transgenic seeds after six seasons of breeding. Thirdly, we examined the feasibility of producing a small peptide in maize seeds. A designed 22 amino acid peptide biosurfactant GAM1 was fused to the C-terminus of a fluoresce protein, the red fluorescent protein (RFP), or a maize seed storage protein, the 22-kDa α-zein, to avoid proteolytic degradation in the cell. While red fluorescence could be detected in seeds carrying RFP fusion construct, we failed to detect the presence of GAM1 despite using various protein concentration and detection methods. Strategies for producing this peptide in maize will need to be redesigned. Lastly, we evaluated two strategies for enhancing recombinant protein expression in maize seeds. In the first strategy, we generated a line with reduced seed storage protein γ-zein by RNA interference (γRNAi). Then we crossed this line with a transgenic line expressing green fluorescent protein (γGFP). The GFP levels in subsequent generations were decreased in the γGFP/γRNAi seeds, which was opposite to what we expected. In the second strategy, we generated a line (oxPBF) constitutively overexpressing the transcription factor prolamin-box binding factor (PBF) that plays regulatory roles to the 27-kDa γ-zein promoter. We intend to cross the oxPBF line with transgenic lines expressing the GFP or recombinant proteins driven by the 27-kDa γ-zein promoter. It is hoped that the PBF overexpression may enhance the production of foreign protein under the γ-zein promoter control. This work indicated that maize has the potential to produce recombinant proteins with mammalian-like post-translational modifications and can be used for open-field production when using a cytoplasmic male-sterile breeding system