766 research outputs found
Replication package for: "Identification and Estimation in Many-to-one Two-sided Matching without Transfers"
No full text<p>He, YingHua, Shruti Sinha, and Xiaoting Sun. "Identification and Estimation in Many-to-one Two-sided Matching without Transfers."</p>
sj-doc-1-npx-10.1177_1934578X231206228 - Supplemental material for Curcumin Protects Pheochromocytoma Cells Against Hydrogen Peroxide-Induced Oxidative Stress
No full textSupplemental material, sj-doc-1-npx-10.1177_1934578X231206228 for Curcumin Protects Pheochromocytoma Cells Against Hydrogen Peroxide-Induced Oxidative Stress by Xiaoting Sun, Lu Chen, Lingli Lin, Kuo-Ting Ho, Shi-Ying Huang, Jian Li, Jingwen Liu, Zhengxiao Zhang and Guiling Li in Natural Product Communications</p
Influence of the surface hydroxyl groups of MnOx/SBA-15 on heterogeneous catalytic ozonation of oxalic acid
No full textComparative ozonation experiments were carried out to investigate the catalytic ability and mechanism of SBA-15 supported manganese oxide (MnOx/SBA-15) for the degradation of oxalic acid (OA) in aqueous solution. The results showed that MnOx/SBA-15 possessed good catalytic capacity for the ozonation of OA. The influences of tert-butanol and phosphate on OA removal and ozone equilibrium concentration in aqueous solution demonstrated that initiation of hydroxyl radicals (radical dotOH) was involved and surface reaction played the major role in O3/MnOx/SBA-15. The effects of manganese content and initial solution pH verified that surface hydroxyl groups affected by the pH of solution and the point of zero charge (pHPZC) of catalysts, were closely related to OA adsorption and radical dotOH initiation on the surface of MnOx/SBA-15. The pre-ozonated catalyst improved its catalytic activity a little due to the enhancement of electron transfer in the presence of higher multivalent MnOx (Mn(III)/Mn(IV)). It was concluded that the protonated surface hydroxyl groups were the main reaction sites and a possible catalytic ozonation mechanism of OA over MnOx/SBA-15 was proposed
In-situ TEM study of carbon nanomaterials and thermoelectric nanomaterials
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from PDF version of thesis.Includes bibliographical references (p. 103-112).Graphene nanoribbons (GNRs) are quasi one dimensional structures which have unique transport properties, and have a potential to open a bandgap at small ribbon widths. They have been extensively studied in recent years due to their high potential for future electronic and spintronic device applications. The edge structures - including the edge roughness and chirality - dramatically affect the transport, electronic, and magnetic properties of GNRs, and are of the critical importance. We have developed an efficient way of modifying the edges structures, to produce atomically smooth zigzag and armchair edges by using insitu TEM with a controlled bias. This work provides us with many opportunities for both fundamental studies and for future applications. I also report the use of either furnace heating or Joule heating to pacify the exposed graphene edges by loop formation in the graphitic nanoribbons. The edge energy minimization process involves the formation of loops between adjacent graphene layers. An estimation of the temperature during in-situ Joule heating is also reported based on the melting and evaporation of Pt nanoparticles. In this thesis work, I have also investigated the morphological and electronic properties of GNRs grown by chemical vapor deposition. Our results suggest that the GNRs have a surprisingly high crystallinity and a clean surface. Both folded and open edges are observed in GNRs. Atomic resolution scanning tunneling microscopy (STM) images were obtained on the folded layer and the bottom layer of the GNR, which enables clear identification of the chirality for both layers. We have also studied the electronic properties of the GNRs using low temperature scanning tunneling spectroscopy (STS). Our findings suggest that edges states exist at GNR edges which are dependent on the chiral angles of the GNRs.by Xiaoting Jia.Ph.D
Inorganic Carbon Pools and Their Drivers in Grassland and Desert Soils
No full textABSTRACT Inorganic carbon is an important component of soil carbon stocks, exerting a profound influence on climate change and ecosystem functioning. Drylands account for approximately 80% of the global soil inorganic carbon (SIC) pool within the top 200 cm. Despite its paramount importance, the components of SIC and their contributions to CO 2 fluxes have been largely overlooked, resulting in notable gaps in understanding its distribution, composition, and responses to environmental factors across ecosystems, especially in deserts and temperate grasslands. Utilizing a dataset of 6011 samples from 173 sites across 224 million hectares, the data revealed that deserts and grasslands in northwestern China contain 20 ± 2.5 and 5 ± 1.3 petagrams of SIC in the top 100 cm, representing 5.5 and 0.76 times the corresponding soil organic carbon stock, respectively. Pedogenic carbonates (PIC), formed by the dissolution and re‐precipitation of carbonates, dominated in grasslands, accounting for 60% of SIC with an area‐weighted density of 3.4 ± 0.4 kg C m −2 at 0–100 cm depth, while lithogenic carbonates (LIC), inherited from soil parent materials, prevailed in deserts, constituting 55% of SIC with an area‐weighted density of 7.1 ± 1.0 kg C m −2 . Soil parent materials and elevation determined the SIC stocks by regulating the formation and loss of LIC in deserts, whereas natural acidification, mainly induced by rhizosphere processes including cation uptake and H + release as well as precipitation, reduced SIC (mainly by PIC) in grasslands. Overall, the massive SIC pool underscores its irreplaceable role in maintaining the total carbon pool in drylands. This study sheds light on LIC and PIC and highlights the critical impact of natural acidification on SIC loss in grasslands.National Key Research and Development Program of China https://doi.org/10.13039/501100012166National Natural Science Foundation of China https://doi.org/10.13039/501100001809Natural Science Foundation of Gansu Province https://doi.org/10.13039/50110000477
Preventing Chronic Disease (PCD)
No full textIntroductionEffective collaboration between public health and the health care system is essential for connecting medical and community health\u2013related resources and improving population health. We investigated the linkages between local health departments and primary care clinics in Nebraska.MethodsWe conducted a mixed-method study by using semi structured in-person and telephone interviews and surveys in 2017 and 2018 with directors of 19 Nebraska local health departments. Interviews and surveys assessed activities and programs that health departments implemented or planned with clinics in their jurisdictions. Barriers, benefits, and opportunities for building the linkages were identified.ResultsStrong linkages existed between local health departments and primary care clinics. Linkages focused on the control and prevention of chronic diseases and on traditional public health programs, including screening for cancer and other chronic diseases, vaccinations, worksite wellness programs, home visits, clinic and medication assistance referrals, health message development, electronic health records data analyses, staff education, and improvements in policies and procedures. The most frequently reported barrier was funding, and the most frequently reported benefit was patient behavior change. The opportunity most frequently reported was chronic disease health coaching.ConclusionExtensive linkages exist between Nebraska local health departments and the health care systems in their areas. Additional funding, effective workforce management, community needs assessments, and program evaluation can support joint initiatives to address community health priorities
Examining the Effects of Approaches on Reducing Hospital Utilization: The Patient-Centered Medical Home, Continuity of Care, and the Inpatient Palliative Consultation at the End-of-Life
No full textBackground: It has become a national priority to reduce the high health care expenditure in the United States while improving the quality of care. Hospital care is taking up one-third of the healthcare spending, and services offered in hospitals are costly compared to others. Only one-twentieth of the patients with high-needs account for about half of the health care spending. They consuming a high level of hospital services if their conditions are not well-managed in the outpatient settings. Therefore, it is important to examine the effectiveness of the approaches that have the potentials to reduce costly care utilization through improvements in the quality of care. This dissertation thesis focused on examining the effects of three approaches to reduce hospital utilization. The three approaches include the patient-centered medical homes (PCMH), better continuity of care (COC), and the early use of inpatient palliative consultation (IPC) at the end of life.
Methods: Andersen’s Behavioral model of health care utilization was used to guide the modeling process of the three individual studies. The first study used data from the Medical Expenditure Panel Survey Household Component (MEPS-HC). Respondents who reported having a usual source of care other than the emergency department (ED) were included, and they were classified into three levels of PCMH groups by their baseline-year care features from 11 selected items. The outcomes were the second-year hospital admissions and ED visits due to the ambulatory care sensitive conditions (ACSCs). Logistic regressions that accounted for survey weights were used. The second study was conducted among a nationally representative Taiwan Population who were admitted for the first time for the five conditions. The outcomes are the numbers of all-cause and condition-specific hospitalizations during the follow-up year after discharge, and the primary explanatory variable was the outpatient COC. Multivariable generalized estimation equation models with a negative binomial distribution and log link were used. The third study used Nebraska Hospital Discharge Data linked with death certificates to identify the inpatient services received by the Nebraska Decedents due to the top six causes of death. The use of IPC was classified by the time receiving it as early use and late use, and the comparison group was the decedents who never encountered IPC. The outcomes were end-of-life events including hospice discharge, place of death, intensive care utilization, life-sustaining treatment, length of stay and total inpatient charges. Mixed-effect logistic regressions, logistic regression, negative binomial regression, and generalized linear model with log link and gamma distribution were used for those outcomes respectively.
Results: The highest level of PCMH primary care was associated with lower risks of having admissions and ED visits due to ACSCs. However, individual attributes of PCMH did not have the same effects. The patients with better COC have significantly fewer all-cause hospitalizations for all the conditions. The COC only worked in patients with ACSC conditions in reducing the condition-specific hospitalizations. The early use of IPC was associated with lower likelihoods of dying in the hospitals, receiving intensive care and the life-sustaining treatment. The use of IPC at either the early or late time was associated with higher odds of being discharged to hospice care, and less length of stay in the inpatient settings and less total inpatient charges.
Conclusion: Approaches such as PCMH, improving continuity of care and the early use of palliative care are promising in reducing the costly hospital services and improving the quality of care. These approaches are replicable to any value-based programs for cost-reduction, quality improvement, and improving population health outcomes
Anonymous, Secure and Efficient Vehicular Communications
No full textVehicular communication networking is a promising approach for facilitating road safety, traffic management, and infotainment dissemination for drivers and passengers. However, it is subject to various malicious abuses and security attacks which hinder it from practical implementation.
In this study, we propose a novel security protocol called GSIS based on group signature and identity-based signature schemes to meet the unique requirements of vehicular communication networks. The proposed protocol not only guarantees security and anonymity, but also provides easy traceability when the identity of the sender of a message has to be revealed by the authority. However, the cryptographic operations introduced in GSIS as well as the existing public key based message authentication protocols incur some computation and communication overhead which affect the system performance. Simulation results show that the GSIS security protocol is only applicable under light traffic conditions in terms of the message end to end delay and message loss ratio.
Both the GSIS protocol and the existing public key based security protocols have to sign and verify all the received messages with asymmetric algorithms. The PKI based approach also has to attach a public key certificate in each packet. Therefore, to enhance the system performance and mitigate the message overhead without compromising the security requirement, this study further proposes an enhanced TESLA based Secure Vehicular Communication (TSVC) protocol. In TSVC, the communication overhead can be significantly reduced due to the MAC tag attached in each packet and only a fast hash operation is required to verify each packet. Simulation results show that TSVC maintains acceptable message latency, using a much smaller packet size, and significantly reduces the message loss ratio as compared to GSIS and existing PKI based protocols, especially when the traffic is denser. We conclude that the proposed approach could serve as good candidate for future vehicular communication networks
Recommended from our members
Essays on Econometrics and its Application to Education
No full textThis dissertation consists of three chapters that study econometrics questions and their applications to education. Chapter 1 studies a nonparametric two-sided many-to-one matching model, where many agents on one side match one institution on the other side. Classical examples include student-college matching and firm-worker matching. In this paper, I study nonparametric identification and estimation of many-to-one matching with non-transferable utility. The existing literature either assumes that the matching algorithm and reported preferences are observed or that preferences are homogeneous. This paper assumes heterogeneous preferences on the two sides and only requires data on who matches with whom in a single large market. Under mild restrictions, I prove that both the utility functions of the students and colleges and the joint distribution of unobserved heterogeneity from the two sides are nonparametrically identified. Based on my constructive identification results, I propose nonparametric and semiparametric estimators of the model and establish their consistency and asymptotic normality. The semiparametric estimator converges at a root-n rate.Chapter 2 analyzes the U.S. college admissions under a many-to-one matching framework. In recovering the parameters of the utility functions, I am able to demonstrate substantial welfare consequences for different groups of students, relative to a centralized matching mechanism. In estimating the model using data from High School Longitudinal Study of 2009 (HSLS:09) and the Integrated Postsecondary Education Data System (IPEDS), I show that the students who experience the largest losses are first-generation college students and low-ability students. This potential loss among these groups provides an opportunity for policy interventions to lead to substantial gains in welfare.Chapter 3 (joint with Kathleen McGarry) studies the three generations of changing gender patterns of schooling in China. The phenomenon of son preference in China and throughout much of Asia has been well documented. However, changing economic conditions, such as increases in educational attainment and employment opportunities for women and the rise in the prevalence of one child families, have likely changed the incentives for parents to invest in daughters. In this paper, we take advantage of data spanning three generations of Chinese families to examine the evolution of educational attainment for boys and girls and importantly the relative levels of schooling of each gender. We also use variation in the timing of compulsory schooling laws and the implementation of the one child policy to assess the effect of these policy measures on the relative educational levels. We find a substantial narrowing of the gap between the schooling of boys and girls, so much so that girls now have more schooling on average than boys. In addition, public policy initiatives had a larger effect in rural than urban areas
- …
