Cooling mechanical resonators to quantum ground state from room temperature

Ground-state cooling of mesoscopic mechanical resonators is a fundamental requirement for test of quantum theory and for implementation of quantum information. We analyze the cavity optomechanical cooling limits in the intermediate coupling regime, where the light-enhanced optomechanical coupling strength is comparable with the cavity decay rate. It is found that in this regime the cooling breaks through the limits in both the strong and weak coupling regimes. The lowest cooling limit is derived analytically at the optimal conditions of cavity decay rate and coupling strength. In essence, cooling to the quantum ground state requires $Q_{\mathrm{m}}>2.4n_{\mathrm{th}}$, with $Q_{\mathrm{m}}$ being the mechanical quality factor and $n_{\mathrm{th}}$ being the thermal phonon number. Remarkably, ground-state cooling is achievable starting from room temperature, when mechanical $Q$-frequency product $Q_{\mathrm{m}}{\nu>1.5}\times10^{13}$, and both of the cavity decay rate and the coupling strength exceed the thermal decoherence rate. Our study provides a general framework for optimizing the backaction cooling of mesoscopic mechanical resonators

Hotel Revenue Management Performance Influencing Mechanism: Theoretical Framework and Research Propositions

Revenue management, a management concept which was first used in the US airline industry and has been widely used in other service industries especially hotel industry because of the significant effect. Especially in recent years, revenue management has become an important competition strategy in the hotel. But so far, academic research about hotel revenue management influence mechanism and performance evaluation is still extremely limited. Based on the influencing factors-decision behavior-performance evaluation logical relationship, combing through the literature review, this paper discussed the relationship between revenue management influence factors and the performance evaluation, proposed the theory framework concerning influence mechanism of hotel revenue management performance evaluation and research propositions

An Empirical Research on Hotel Revenue Management Financial Performance Influencing Factors

In recent years, revenue management has become an important competitive strategy in the hotel, and the level of hotel performance directly reflects the effectiveness of the application of revenue management. But so far, academic research about hotel revenue management performance influencing mechanism and evaluation is still extremely limited. Based on fully retrieving the relevant literature, the author summarized the factors affecting revenue management financial performance and built a conceptual model, using structural equation model (SEM) to verify and correct it. Then the author concluded: hotel quality attributes which contain hotel scale, star rating, owner type and management company type have no significant effect on hotel revenue management performance; technical drivers which include pricing and non-pricing factors have significant positive impact on RM performance, and the impact of pricing tools is more intense; organizational drivers including organizational support, manager quality, incentive and training have positive impact on RM performance, second only to pricing tools; and finally, organizational drivers had significant impact on technical drivers

Effects of L-carnitine against oxidative stress in human hepatocytes: involvement of peroxisome proliferator-activated receptor alpha

<p>Abstract</p> <p>Background</p> <p>Excessive oxidative stress and lipid peroxidation have been demonstrated to play important roles in the production of liver damage. L-carnitine is a natural substance and acts as a carrier for fatty acids across the inner mitochondrial membrane for subsequent beta-oxidation. It is also an antioxidant that reduces metabolic stress in the cells. Recent years L-carnitine has been proposed for treatment of various kinds of disease, including liver injury. This study was conducted to evaluate the protective effect of L-carnitine against hydrogen peroxide (H₂O₂)-induced cytotoxicity in a normal human hepatocyte cell line, HL7702.</p> <p>Methods</p> <p>We analyzed cytotoxicity using MTT assay and lactate dehydrogenase (LDH) release. Antioxidant activity and lipid peroxidation were estimated by reactive oxygen species (ROS) levels, activities and protein expressions of superoxide dismutase (SOD) and catalase (CAT), and malondialdehyde (MDA) formation. Expressions of peroxisome proliferator-activated receptor (PPAR)-alpha and its target genes were evaluated by RT-PCR or western blotting. The role of PPAR-alpha in L-carnitine-enhanced expression of SOD and CAT was also explored. Statistical analysis was performed by a one-way analysis of variance, and its significance was assessed by Dennett's post-hoc test.</p> <p>Results</p> <p>The results showed that L-carnitine protected HL7702 cells against cytotoxity induced by H₂O₂. This protection was related to the scavenging of ROS, the promotion of SOD and CAT activity and expression, and the prevention of lipid peroxidation in cultured HL7702 cells. The decreased expressions of PPAR-alpha, carnitine palmitoyl transferase 1 (CPT1) and acyl-CoA oxidase (ACOX) induced by H₂O₂can be attenuated by L-carnitine. Besides, we also found that the promotion of SOD and CAT protein expression induced by L-carnitine was blocked by PPAR-alpha inhibitor MK886.</p> <p>Conclusions</p> <p>Taken together, our findings suggest that L-carnitine could protect HL7702 cells against oxidative stress through the antioxidative effect and the regulation of PPAR-alpha also play an important part in the protective effect.</p