Methods for backcasting,nowcasting and forecasting using factor‐MIDAS: With an application to Korean GDP

We utilize mixed‐frequency factor‐MIDAS models for the purpose of carrying out backcasting, nowcasting, and forecasting experiments using real‐time data. We also introduce a new real‐time Korean GDP dataset, which is the focus of our experiments. The methodology that we utilize involves first estimating common latent factors (i.e., diffusion indices) from 190 monthly macroeconomic and financial series using various estimation strategies. These factors are then included, along with standard variables measured at multiple different frequencies, in various factor‐MIDAS prediction models. Our key empirical findings as follows. (i) When using real‐time data, factor‐MIDAS prediction models outperform various linear benchmark models. Interestingly, the “MSFE‐best” MIDAS models contain no autoregressive (AR) lag terms when backcasting and nowcasting. AR terms only begin to play a role in “true” forecasting contexts. (ii) Models that utilize only one or two factors are “MSFE‐best” at all forecasting horizons, but not at any backcasting and nowcasting horizons. In these latter contexts, much more heavily parametrized models with many factors are preferred. (iii) Real‐time data are crucial for forecasting Korean gross domestic product, and the use of “first available” versus “most recent” data “strongly” affects model selection and performance. (iv) Recursively estimated models are almost always “MSFE‐best,” and models estimated using autoregressive interpolation dominate those estimated using other interpolation methods. (v) Factors estimated using recursive principal component estimation methods have more predictive content than those estimated using a variety of other (more sophisticated) approaches. This result is particularly prevalent for our “MSFE‐best” factor‐MIDAS models, across virtually all forecast horizons, estimation schemes, and data vintages that are analyzed.     

Systematic pathway analysis using high-resolution fitness profiling of combinatorial gene deletions

Systematic genetic interaction studies have illuminated many cellular processes. Here we quantitatively examine genetic interactions among 26 Saccharomyces cerevisiae genes conferring resistance to the DNA-damaging agent methyl methanesulfonate (MMS), as determined by chemogenomic fitness profiling of pooled deletion strains. We constructed 650 double-deletion strains, corresponding to all pairings of these 26 deletions. The fitness of single- and double-deletion strains were measured in the presence and absence of MMS. Genetic interactions were defined by combining principles from both statistical and classical genetics. The resulting network predicts that the Mph1 helicase has a role in resolving homologous recombination-derived DNA intermediates that is similar to (but distinct from) that of the Sgs1 helicase. Our results emphasize the utility of small molecules and multifactorial deletion mutants in uncovering functional relationships and pathway order.     

空间分析中GIS和空间语法理论的应用

运用GIS技术和空间语法论考察了新城市建设等城市计划中形成的土地利用变化和城市空间结构特征。以上世纪九十年代建设坪村新城市的安阳市设定为研究对象,分析了城市空间结构。特别是以公路网为中心,分析了城市空间结构和商业设施分布的相互关系,且查看了由大规模建筑区开发所引起的城市空间中心的移动。通过此项研究能综合运用空间语法论和GIS探索空间结构的特征,并把它应用于GIS所被利用的各种领域。     

Greenhouse Effects in Global Warming based on Analogical Reasoning

Using an analogy in science and everyday life is a double-edged sword because they are accompanied by alternative ideas, in addition to scientific concepts. Schools and public education explain global warming by making a common analogy between this phenomenon and greenhouse effects (Chen in Philos Cogn Sci 105–114, 2012). Unfortunately, this analogy sometimes produces various incorrect explanatory mental models. To construct a correct understanding of global warming, it is necessary: first, to investigate the attributes of analogical reasoning; second, to understand these features by restructuring the greenhouse analogy; and third, to explore the problems and benefits of the greenhouse analogy. The characteristics of relations, rather than objects, must be mapped according to the principle of systematicity, but the public tends to preserve the attributes of the base domain, which is mapped relatively easily. In conclusion, certain facets of the prevailing greenhouse analogy cause a distorted public view of climate change. We must use the greenhouse analogy and yet simultaneously emphasize the relations and attributes highlighted and hidden in the analogy during evaluation.     

S-nitrosylation of NADPH oxidase regulates cell death in plant immunity

Changes in redox status are a conspicuous feature of immune responses in a variety of eukaryotes, but the associated signalling mechanisms are not well understood. In plants, attempted microbial infection triggers the rapid synthesis of nitric oxide and a parallel accumulation of reactive oxygen intermediates, the latter generated by NADPH oxidases related to those responsible for the pathogen-activated respiratory burst in phagocytes. Both nitric oxide and reactive oxygen intermediates have been implicated in controlling the hypersensitive response, a programmed execution of plant cells at sites of attempted infection. However, the molecular mechanisms that underpin their function and coordinate their synthesis are unknown. Here we show genetic evidence that increases in cysteine thiols modified using nitric oxide, termed S-nitrosothiols, facilitate the hypersensitive response in the absence of the cell death agonist salicylic acid and the synthesis of reactive oxygen intermediates. Surprisingly, when concentrations of S-nitrosothiols were high, nitric oxide function also governed a negative feedback loop limiting the hypersensitive response, mediated by S-nitrosylation of the NADPH oxidase, AtRBOHD, at Cys 890, abolishing its ability to synthesize reactive oxygen intermediates. Accordingly, mutation of Cys 890 compromised S-nitrosothiol-mediated control of AtRBOHD activity, perturbing the magnitude of cell death development. This cysteine is evolutionarily conserved and specifically S-nitrosylated in both human and fly NADPH oxidase, suggesting that this mechanism may govern immune responses in both plants and animals.     

Glutamate induces de novo growth of functional spines in developing cortex

Mature cortical pyramidal neurons receive excitatory inputs onto small protrusions emanating from their dendrites called spines. Spines undergo activity-dependent remodelling, stabilization and pruning during development, and similar structural changes can be triggered by learning and changes in sensory experiences. However, the biochemical triggers and mechanisms of de novo spine formation in the developing brain and the functional significance of new spines to neuronal connectivity are largely unknown. Here we develop an approach to induce and monitor de novo spine formation in real time using combined two-photon laser-scanning microscopy and two-photon laser uncaging of glutamate. Our data demonstrate that, in mouse cortical layer 2/3 pyramidal neurons, glutamate is sufficient to trigger de novo spine growth from the dendrite shaft in a location-specific manner. We find that glutamate-induced spinogenesis requires opening of NMDARs (N-methyl-D-aspartate-type glutamate receptors) and activation of protein kinase A (PKA) but is independent of calcium-calmodulin-dependent kinase II (CaMKII) and tyrosine kinase receptor B (TrkB) receptors. Furthermore, newly formed spines express glutamate receptors and are rapidly functional such that they transduce presynaptic activity into postsynaptic signals. Together, our data demonstrate that early neural connectivity is shaped by activity in a spatially precise manner and that nascent dendrite spines are rapidly functionally incorporated into cortical circuits.