Novel Optical Applications Based on Photon-phonon Interactions

The phenomena of photon-phonon interactions can be found in all forms of matters including gases, plasma, liquids and solids. The applications based on such interactions, including Raman scattering, Bragg Scattering, polariton resonance, phonon-assisted Antistoke photoluminescence, etc. has been intensively investigated. In this dissertation, we present our study of three novel applications in the field of THz generation, hot phonons in transistors, and optical refrigeration. In Chapter 1, we studied the backward propagating Terahertz (THz) generation using optical rectification in periodically poled LiNbO3 and LiTaO3 samples with ultrafast laser pulse excitation. With the LiNbO3 sample, we have generated the highest frequency at 4.8 THz at the poling period of 7.1 µm, corresponding to an output wavelength of 62.5 µm. We have observed an enhancement factor as large as 61 in the output power comparing to that generated from bulk LiNbO3, which was attributed to the phonon polariton resonance-enhanced nonlinear optical coefficients. For the LiTaO3 samples, we have reached the highest output power of nearly 100 µW. Based on our study, the effective second-order nonlinear coefficient of LiTaO3 are enhance by factors of from 3.7 to 23, leading to the enhancement of THz output powers. The enhancement is rooted in a polariton resonance at the frequency of 127 cm-1, which can be induced by the nonlinear mixing of two transverse-optical phonons due to strong anharmonicity of LiTaO3. We also designed a second wafer with significantly shorter poling periods, and indeed we have observed the entire resonant peak. In Chapter 2, we studied the hot phonon behavior of GaN high electron mobility transistors (HEMT). We mainly investigated our effort on two methods utilizing Raman scattering to measure the phonon temperature, i.e. the hot phonon population of GaN HEMT device under operation. The ultimate goal was to employ these methods on the study of isotope disorder introduced GaN device and verify whether its phonon behavior is optimized than that in normal devices. The first method extracts phonon temperatures from the ratio of Antistokes and Stokes Raman signal intensities, which requires complex experimental procedures and tendency to wrong temperature deductions. The second method is based on the fitting of phonon temperature to the shift of Stokes Raman peak model, which leads to simple and fast measurement while sophisticated analysis with strong dependence to sample material properties. Comparing two methods, we believe the second one is advantageous due to our limited experimental condition, and it can be improved with proper calibration of the model. In Chapter 3, we studied the upconverstion of photoluminescence (PL) from both a free-standing bulk GaN sample and a GaN nanowire sample. When the excitation energy is in the tail of bandgap edge, the PL upconverstion can be attributed to phonon-assisted Antistokes photoluminescence (ASPL). We explored the potential of laser cooling based on such a phenomena with the analysis of PL intensity trending with pump power, excitation wavelength, and temperature. Such analysis proves the fact that the ASPL we measured is originated in single photon process assisted by phonons

An Empirical Study on use of Social Media in the Hotel Industry in China: A Study of Customers’ Preferences and Attitudes

With the development of the technology, business corporations start to use social media to promote their businesses. This study focuses on the preferences and attitudes of travelers’ in China with the relationship between usage of social media (based on WeChat and Sina Weibo) with the option of hotel choice in the hospitality industry. There are two instruments used in this study: (1) sending out online surveys and (2) scheduled interviews with people who are working in the hotel industry. From our survey data (N=245) were participants who completed questionnaires located all over China. However, the results of the study indicate that participating hotels and online tickets firms prefer to use social media to attract guests and even potential consumers. The top about three elements that influence decision making of hotel choice are: price (71.84%); location (68.16%); and online rating (33.06%)

On Heterogeneous Neighbor Discovery in Wireless Sensor Networks

Neighbor discovery plays a crucial role in the formation of wireless sensor networks and mobile networks where the power of sensors (or mobile devices) is constrained. Due to the difficulty of clock synchronization, many asynchronous protocols based on wake-up scheduling have been developed over the years in order to enable timely neighbor discovery between neighboring sensors while saving energy. However, existing protocols are not fine-grained enough to support all heterogeneous battery duty cycles, which can lead to a more rapid deterioration of long-term battery health for those without support. Existing research can be broadly divided into two categories according to their neighbor-discovery techniques---the quorum based protocols and the co-primality based protocols.In this paper, we propose two neighbor discovery protocols, called Hedis and Todis, that optimize the duty cycle granularity of quorum and co-primality based protocols respectively, by enabling the finest-grained control of heterogeneous duty cycles. We compare the two optimal protocols via analytical and simulation results, which show that although the optimal co-primality based protocol (Todis) is simpler in its design, the optimal quorum based protocol (Hedis) has a better performance since it has a lower relative error rate and smaller discovery delay, while still allowing the sensor nodes to wake up at a more infrequent rate.Comment: Accepted by IEEE INFOCOM 201

Current evidences on XPC polymorphisms and gastric cancer susceptibility: a meta-analysis

BACKGROUND: Reduced DNA repair capacities due to inherited polymorphisms may increase the susceptibility to cancers including gastric cancer. Previous studies investigating the association between Xeroderma Pigmentosum group C (XPC) gene polymorphisms and gastric cancer risk reported inconsistent results. We performed a meta-analysis to summarize the possible association. METHODS: All studies published up to January 2014 on the association between XPC polymorphisms and gastric cancer risk were identified by searching electronic databases PubMed, EMBASE, Cochrane library, and Chinese Biomedical Literature database (CBM). The association between XPC polymorphisms and gastric cancer risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs). RESULTS: Six studies with 1,355 gastric cancer cases and 2,573 controls were finally included in the meta-analysis. With respect to Lys939Gln polymorphism, we did not observe a significant association when all studies were pooled into the meta-analysis. When stratified by ethnicity, source of control, and study quality, statistical significant association was not detected in all subgroups. With respect to Ala499Val and PAT−/+polymorphisms, we also did not observe any significant association with gastric cancer risk in the pooled analysis. CONCLUSIONS: This meta-analysis based on current evidences suggested that the XPC polymorphisms (Lys939Gln, Val499Arg, and PAT−/+) did not contribute to gastric cancer risk. Considering the limited sample size and ethnicity included in the meta-analysis, further larger scaled and well-designed studies are needed to confirm our results. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/148588031255506

Cationic lipid-assisted nanoparticles for simultaneous delivery of CD47 siRNA and R848 to promote antitumor immune responses

Introduction: Triple-negative breast cancer (TNBC) usually has a poor prognosis. Although the immunotherapy of TNBC has achieved great progress, only a few patients can benefit from the current treatment. CD47 is widely expressed on the surface of TNBC cells and may become an immune checkpoint for TNBC treatment. Nevertheless, increasingly more attention has been paid to systemic side effects since the ubiquitous expression of CD47 on normal cells. The toll-like receptor (TLR) agonist resiquimod (R848) can activate dendritic cells (DCs) and promote the maturation of immune cells in the tumor microenvironment, which further enhances the tumor inhibition ability of the immune system and synergizes with CD47 small interfering RNA (siRNA) for TNBC therapy. However, ideal delivery platforms such as nanocarriers are still needed because its weakness of hydrophobicity.Methods: In order to improve efficacy and reduce toxicity, R848 and siCD47 were entrapped in amphiphilic PEG-PLGA nanoparticles by double emulsification and stable nanoparticles NP/R848/siCD47 were generated to investigate their anti-tumor effects in a TNBC tumor-bearing mouse model.Results: Here, we show that PEG-PLGA nanoparticles are effective nanocarriers that can safely and effectively deliver siCD47 and R848 to tumor tissue, as demonstrated by retarded tumor growth. Mechanistically, downregulation of CD47 expression and activation of DCs took part in promoting the immune response of cytotoxic T cells (CTLs). Meanwhile, a decrease of myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) indicated the modulating of the tumor immune microenvironment.Discussion: To our best knowledge, our study pioneered co-delivery system for hydrophilic siCD47 and hydrophobic R848. It can maximize break tumor immune escape caused by CD47 and simultaneously enhance antigen presentation by activating DCs for effector T cell killing while regulating the tumor microenvironment as expected. Not only does it conform to the reports of previous basic research, but also it can break the bottleneck of their clinical application hopefully. Collectively, our findings could lay the foundation for future therapeutic strategies of TNBC

Associations of 10 dietary habits with breast cancer: a Mendelian randomization study

IntroductionEpidemiological studies have revealed a link between dietary habits and the breast cancer risk. The causality of the association between food consumption and breast cancer requires further investigation.MethodsUsing Mendelian randomization, we assessed the causal effects of 10 dietary habits on the risks of breast cancer and its subtypes (estrogen receptor [ER]  +  and ER- breast cancer). We obtained dietary pattern data in 2018 (number of single-nucleotide polymorphisms [SNPs]  =  9,851,867) and breast cancer data in 2017 (number of SNPs  =  10,680,257) from IEU OpenGWAS. Rigorous sensitivity analyses were conducted to ensure that the study results were credible and robust.ResultsWe identified that genetic predisposition to higher dried fruit intake was linked to a reduced risk of overall breast cancer (inverse variance-weighted [IVW] odds ratio [OR] = 0.55; 95% confidence interval [CI]: 0.43–0.70; p = 1.75 × 10−6), ER+ breast cancer (IVW OR = 0.62; 95% CI: 0.47–0.82; p = 8.96 × 10−4) and ER− breast cancer (IVW OR = 0.48; 95% CI: 0.34–0.68; p = 3.18 × 10−5), whereas genetic predisposition to more oily fish intake was linked to a lower risk of ER+ breast cancer (IVW OR = 0.73; 95% CI: 0.53–0.99; p = 0.04).DiscussionOur findings suggest that a genetic predisposition for dried fruit and oily fish consumption may be protective against breast cancer; however, further investigation is required

Detection of Thermal Covert Channel Attacks Based on Classification of Components of the Thermal Signal Features

In response to growing security challenges facing many-core systems imposed by thermal covert channel (TCC) attacks, a number of threshold-based detection methods have been proposed. In this paper, we show that these threshold-based detection methods are inadequate to detect TCCs that harness advanced signaling and specific modulation techniques. Since the frequency representation of a TCC signal is found to have multiple side lobes, this important feature shall be explored to enhance the TCC detection capability. To this end, we present a pattern-classification-based TCC detection method using an artificial neural network that is trained with a large volume of spectrum traces of TCC signals. After proper training, this classifier is applied at runtime to infer TCCs, should they exist. The proposed detection method is able to achieve a detection accuracy of 99%, even in the presence of the stealthiest TCCs ever discovered. Because of its low runtime overhead (<0.187%) and low energy overhead (<0.072%), this proposed detection method can be indispensable in fighting against TCC attacks in many-core systems. With such a high accuracy in detecting TCCs, powerful countermeasures, like the ones based on dynamic voltage and frequency scaling (DVFS), can be rightfully applied to neutralize any malicious core participating in a TCC attack

A large scale hearing loss screen reveals an extensive unexplored genetic landscape for auditory dysfunction

The developmental and physiological complexity of the auditory system is likely reflected in the underlying set of genes involved in auditory function. In humans, over 150 non-syndromic loci have been identified, and there are more than 400 human genetic syndromes with a hearing loss component. Over 100 non-syndromic hearing loss genes have been identified in mouse and human, but we remain ignorant of the full extent of the genetic landscape involved in auditory dysfunction. As part of the International Mouse Phenotyping Consortium, we undertook a hearing loss screen in a cohort of 3006 mouse knockout strains. In total, we identify 67 candidate hearing loss genes. We detect known hearing loss genes, but the vast majority, 52, of the candidate genes were novel. Our analysis reveals a large and unexplored genetic landscape involved with auditory function