Use of Pseudo-observations in the Goodness-of-Fit Test for Gray\u27s Time-Varying Coefficients Model

Background The Cox proportional hazards (PH) regression model is the most common method to estimate underlying survival or failure probabilities and to estimate the effects of covariates on survival times. In Cox PH models, the regression coefficients are assumed constant over time. However, if covariate effects vary over time, alternative models which do not necessarily assume proportionality are needed. Method We proposed the Gray’s time-varying coefficient (TVC) method based on pseudo-observation. By using pseudo-observations, pseudo-residuals were calculated and plotted against the estimated survival rates at each of the nine selected time points, then were used to evaluate the goodness-of-fit of the Gray’s model. We applied this method to assess the fit for a model that predicts post-transplant survival probability among children who were under the age of 12 years, had end-stage liver disease, and underwent liver transplantation between January 2005 and June 2010. Result For Gray’s TVC model, through the first time point and the sixth time point, pseudo residual plots are around zero, while pseudo residual plots show slight departure at small values of estimated survival rate through the seventh time point and the ninth time point. Since the pseudo residual plots stay around zero at each time point without any significant departure or tendency, we can conclude that Gray’s model shows a good fit in estimating survival function at each time point. The results from this real liver transplantation data demonstrate that the final Gray’s model shows a good fit in estimating post-transplant survival. Conclusion When data violate the PH assumption, the Gray TVC model or an alternative should be used to obtain unbiased estimates on survival function and give correct inference on the relationship between potential covariates and survival. The proposed goodness-of-fit test offers a tool to investigate how well the model fits the data

Minimal Width for Universal Property of Deep RNN

A recurrent neural network (RNN) is a widely used deep-learning network for dealing with sequential data. Imitating a dynamical system, an infinite-width RNN can approximate any open dynamical system in a compact domain. In general, deep networks with bounded widths are more effective than wide networks in practice; however, the universal approximation theorem for deep narrow structures has yet to be extensively studied. In this study, we prove the universality of deep narrow RNNs and show that the upper bound of the minimum width for universality can be independent of the length of the data. Specifically, we show that a deep RNN with ReLU activation can approximate any continuous function or $L^p$ function with the widths $d_x+d_y+2$ and $\max\{d_x+1,d_y\}$, respectively, where the target function maps a finite sequence of vectors in $\mathbb{R}^{d_x}$ to a finite sequence of vectors in $\mathbb{R}^{d_y}$. We also compute the additional width required if the activation function is $\tanh$ or more. In addition, we prove the universality of other recurrent networks, such as bidirectional RNNs. Bridging a multi-layer perceptron and an RNN, our theory and proof technique can be an initial step toward further research on deep RNNs

BIOFUEL PRODUCTION FROM BIOMASS-DERIVED VOLATILE FATTY ACID PLATFORM

The typical biorefinery platforms are sugar, thermochemical (syngas), carbon-rich chains, and biogas platform. The sugar platform uses hexose and pentose sugars extracted or converted from plant body. The thermochemical (syngas) platform is chemical or biological conversion process using pyrolysis or gasification of plant to produce biofuels. The carbon-rich chains platform is used to produce biodiesel from long-chain fatty acids or glycerides. Those platforms have unique advantages and disadvantages. Our group has concentrated on the biogas platform producing methane gas from municipal solid wastes through anaerobic digestion (AD) processs, which is composed of rapid acidogenesis and slow methanogenesis. This acidogenic and methanogenic process is widely used for biogas production form the treatment of wetted waste materials (foodwastes, sludge, and manure) in the worldwide. The volatile fatty acids (VFAs) are short-chain fatty acids composed of mainly acetate and butyrate, and easily produced from non-woody biomass with low lignin content in acidogenesis step by the natural consortia of mixed anaerobic bacteria. And then it is slowly converted to biogas (methane, CO2) by methanogenic bacteria naturally. Now, we would like to suggest a new platform using VFAs for biofuel and biochemicals production, because the VFAs can be produced form a cost-effective way using AD process that does not need sterilization, additional hydrolysis enzymes (cellulase and xylanase) and high cost pretreatment step in case of low-lignin content biomass. Considering that raw material alone constitutes 60-80% of biofuel production costs, biofuels made from the VFAs derived from the waste organic biomass can have a potential of economical advantage. A problem is how to convert VFAs to biofuels and biochemicals. In the presentation, we will give possible solutions in order to produce bioethanol, biobutanol, biodiesel, and biohydrogen as well as biogas through biological or chemical processes. And we will introduce our ongoing researches related with the VFA platfor

Splenectomy is associated with an aggressive tumor growth pattern and altered host immunity in an orthotopic syngeneic murine pancreatic cancer model.

The purpose of this study was to investigate whether splenectomy influences the tumor growth and metastatic pattern in an orthotopic syngeneic murine pancreatic cancer model. Murine pancreatic cancer cells (PAN02) were subcutaneously injected into the flanks of nude mice. A small tumor fragment (3 mm2), harvested from a subcutaneous tumor. was orthotopically implanted in the tail of the pancreas of C57/BL6 mice without splenectomy (control group, n=15) or with simultaneous splenectomy (splenectomy group, n=15). Tumor growth and metastatic patterns were analyzed by laparotomy at 21 days after surgery. No tumor growth was found in 5 mice (33.3%) of the control group and 1 mouse (6.7%) of the splenectomy group (p=0.169). Tumor volume was significantly larger in splenectomy group (p=0.013). Peritoneal seeding was more frequently observed in the splenectomy group (11 (73.3%) vs. 4 (26.7%), p=0.011). There were no differences in the number of liver and kidney metastasis between the two groups. The ratios of tumor-infiltrating CD4+ to FoxP3+ and CD8+ to FoxP3+ were significantly higher in the control group compared to the splenectomy group (8.2 ± 9.3 vs. 2.4 ± 1.5, p=0.046; 2.5 ± 1.4 vs. 1.5 ± 0.4, p=0.031, respectively). Splenectomy enhanced tumor growth and peritoneal seeding in an orthotopic syngeneic murine pancreatic cancer mouse model. The ramification of these results are discussed for pancreatic cancer treatment

Temperature-scaling behavior of the Hall conductivity for Hg-based superconducting thin films

The Hall conductivities of HgBa_{2}CaCu_{2}O_{6+\delta}and HgBa_{2}Ca_{2}Cu_{3}O_{8+\delta} thin films are investigated for a magnetic field parallel to the c axis. The mixed-state Hall conductivity for these compounds is well described by \sigma_{xy}=C_{1}/H+C_{2}+C_{3}H. The prefactor C_1 shows a temperature dependence of the form C_1 = A(1-t)^n near T_c, where t=T/T_c is the reduced temperature. Contrary to the previous results, C_2 also follows a temperature-scaling behavior similar to that of the coefficient C_1. The observed value of n = 1.8 - 2.3 is comparable to the previously observed values for YBa_{2}Cu_{3}O_{7-\delta} and La_{2-x}Sr_{x}CuO_{4}.Comment: 5 pages, 4 eps figure

Gap Analysis Between the Level of Heat Wave Adaptation Policy and Heat Wave Effects in South Korean Municipalities

This study aims to analyze the gap between the level of heat wave adaptation policies and heat wave effects in South Korean municipalities. First, the types of industries in municipalities were classified using factor analysis and cluster analysis. Second, the level of heat wave adaptation policy in the municipalities was assessed using a fuzzy analytic hierarchy process analysis. Third, the gap between the level of heat wave adaptation policy and the heat wave effect was analyzed. The results show that the heat wave adaptation policies were established in accordance with the heat wave effects to at least some degree. However, closer to the long-term future (2095), the policies have not sufficiently matched the level of heat wave effects. The proportion of municipalities with insufficient levels of heat wave adaptation policies against the heat wave effects was higher among urban-type municipalities. The analysis results suggest two policy implications. First, the heat wave adaptation policies of municipalities should be established through continuous feedback on the predictions of future heat wave effects. Second, urban-type municipalities should strengthen their planning authority and competence by securing a professional workforce and budgets for the establishment of heat wave adaptation policies

Competing spin-fluctuations in Sr2_2RuO4_4 and their tuning through epitaxial strain

In this study, we report the magnetic energy landscape of Sr2RuO4 employing the generalized Bloch approach within density functional theory. We identify the two dominant magnetic instabilities, ferromagnetic and spin-density-wave, together with other predominant instabilities. We show that epitaxial strain can change the overall magnetic tendency of the system, and tune the relative weight of the various magnetic instabilities in the system. Especially, the balance between spin-density wave and ferromagnetic instabilities can be controlled by the strain, and, eventually can lead to the new magnetic phases as well as superconducting phases with possibly altered pairing channels. Our findings are compared with previous theoretical models and experimental reports for the various magnetic features of the system and offer a first-principles explanation to them

Tunable electronic and magnetic phases in layered ruthenates: SrRuO3-SrTiO3 heterostructure upon strain

Layered ruthenates are a unique class of systems which manifests a variety of electronic and magnetic features emerged from competing energy scales. At the heart of such features lies the multi-orbital physics, especially, the orbital-selective behavior. Here, we propose that the SrRuO3-SrTiO3 heterostructure is a highly tunable platform to obtain the various emergent properties. Employing the density functional theory plus dynamical mean-field theory, we thoroughly investigate the orbital-dependent physics of the system and identify the competing magnetic fluctuations. We show that the epitaxial strain drives the system towards multi-orbital or orbital selective Mott phases from the Hund metal regime. At the same time, the two different types of static magnetism are stabilized, ferromagnetism and checkerboard antiferromagnetism, from the competition with the spin-density wave instability.Comment: 5 pages, 3 figures in the main text, Supplemental Material is include