Information Acquisition and Learning from Prices Over the Business Cycle

We study firms’ incentives to acquire costly information in booms and recessions to understand the role of endogenous information in explaining business cycles. We find that when the economy has been in a boom in the previous period, and firms enter the current period with an optimistic belief, the incentive to acquire information is weaker than when the economy has been in a recession and firms share a pessimistic belief. However, the price system, by transmitting information from informed to uninformed firms, dampens information demand and moderates the cyclicality of the aggregate learning outcome. Even though learning from equilibrium prices acts to stabilize fluctuations by discouraging information acquisition, it can be welfare-enhancing to make information prohibitively costly to obtain.information acquisition; rational expectations equilibrium; asymmetric information; strategic substitutability

On the Complexity of Exact Pattern Matching in Graphs: Binary Strings and Bounded Degree

Exact pattern matching in labeled graphs is the problem of searching paths of a graph $G=(V,E)$ that spell the same string as the pattern $P[1..m]$. This basic problem can be found at the heart of more complex operations on variation graphs in computational biology, of query operations in graph databases, and of analysis operations in heterogeneous networks, where the nodes of some paths must match a sequence of labels or types. We describe a simple conditional lower bound that, for any constant $\epsilon>0$, an $O(|E|^{1 - \epsilon} \, m)$-time or an $O(|E| \, m^{1 - \epsilon})$-time algorithm for exact pattern matching on graphs, with node labels and patterns drawn from a binary alphabet, cannot be achieved unless the Strong Exponential Time Hypothesis (SETH) is false. The result holds even if restricted to undirected graphs of maximum degree three or directed acyclic graphs of maximum sum of indegree and outdegree three. Although a conditional lower bound of this kind can be somehow derived from previous results (Backurs and Indyk, FOCS'16), we give a direct reduction from SETH for dissemination purposes, as the result might interest researchers from several areas, such as computational biology, graph database, and graph mining, as mentioned before. Indeed, as approximate pattern matching on graphs can be solved in $O(|E|\,m)$ time, exact and approximate matching are thus equally hard (quadratic time) on graphs under the SETH assumption. In comparison, the same problems restricted to strings have linear time vs quadratic time solutions, respectively, where the latter ones have a matching SETH lower bound on computing the edit distance of two strings (Backurs and Indyk, STOC'15).Comment: Using Lemma 12 and Lemma 13 might to be enough to prove Lemma 14. However, the proof of Lemma 14 is correct if you assume that the graph used in the reduction is a DAG. Hence, since the problem is already quadratic for a DAG and a binary alphabet, it has to be quadratic also for a general graph and a binary alphabe

Firm size, managerial practices and innovativeness: some evidence from Finnish manufacturing

In this study we use a survey data on 398 Finnish manufacturing firms for the years 2002 and 2005 to empirically explore whether and which organizational factors explain why certain firms produce larger innovative research output than others, and whether the incentives to innovate that certain organizational practices generate differ between small and large firms, and between those firms that are operating in low-tech and high-tech industries. Our study indicates that there appear to be vast differences in the organizational practices leading to more innovation both between small and large firms, and between the firms that operate in high- and low-tech industries. While innovation in small firms benefits from the practices that enhance employee participation in decision-making, large firms that have more decentralized decision-making patterns do not seem to innovate more than those with a more bureaucratic decision-making structure. The most efficient incentive for innovation among the sampled companies seems to be the ownership of a firm's stocks by employees and/or managers. Performance based wages also relates positively to innovation, but only when it is combined with a systematic monitoring of the firm's performance.Innovation, firm size; organizational practices; HRM practices

Automatic Spatial Calibration of Ultra-Low-Field MRI for High-Accuracy Hybrid MEG--MRI

With a hybrid MEG--MRI device that uses the same sensors for both modalities, the co-registration of MRI and MEG data can be replaced by an automatic calibration step. Based on the highly accurate signal model of ultra-low-field (ULF) MRI, we introduce a calibration method that eliminates the error sources of traditional co-registration. The signal model includes complex sensitivity profiles of the superconducting pickup coils. In ULF MRI, the profiles are independent of the sample and therefore well-defined. In the most basic form, the spatial information of the profiles, captured in parallel ULF-MR acquisitions, is used to find the exact coordinate transformation required. We assessed our calibration method by simulations assuming a helmet-shaped pickup-coil-array geometry. Using a carefully constructed objective function and sufficient approximations, even with low-SNR images, sub-voxel and sub-millimeter calibration accuracy was achieved. After the calibration, distortion-free MRI and high spatial accuracy for MEG source localization can be achieved. For an accurate sensor-array geometry, the co-registration and associated errors are eliminated, and the positional error can be reduced to a negligible level.Comment: 11 pages, 8 figures. This work is part of the BREAKBEN project and has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 68686

Phylogeography and Adaptive Divergence of Three-spined Stickleback Populations

Genetic studies on phylogeography and adaptive divergence in Northern Hemisphere fish species such as three-spined stickleback (Gasterosteus aculeatus) provide an excellent opportunity to investigate genetic mechanisms underlying population differentiation. According to the theory, the process of population differentiation results from a complex interplay between random and deterministic processes as well historical factors. The main scope in this thesis was to study how historical factors like the Pleistocene ice ages have shaped the patterns molecular diversity in three-spined stickleback populations in Europe and how this information could be utilized in the conservation genetic context. Furthermore, identifying footprints of natural selection at the DNA level might be used in identifying genes involved in evolutionary change. Overall, the results from phylogeographic studies indicate that the three-spined stickleback has colonized the Atlantic basin relatively recently but constitutes three major evolutionary lineages in Europe. In addition, the colonization of freshwater appears to result from multiple and independent invasions by the marine conspecifics. Molecular data together with morphology suggest that the most divergent freshwater populations are located in the Balkan Peninsula and these populations deserve a special conservation genetic status without warranting further taxonomical classification. In order to investigate the adaptive divergence in Fennoscandian three-spined stickleback populations several approaches were used. First, sequence variability in the Eda-gene, coding for the number of lateral plates, was concordant with the previously observed global pattern. Full plated allele is in high frequencies among marine populations whereas low plated allele dominates in the freshwater populations. Second, a microsatellite based genome scan identified both indications of balancing and directional selection in the three-spined stickleback genome, i.e. loci with unusually similar or unusually different allele frequencies over populations. The directionally selected loci were mainly associated with the adaptation to freshwater. A follow up study conducting a more detailed analysis in a chromosome region containing a putatively selected gene locus identified a fairly large genomic region affected by natural selection. However, this region contained several gene predictions, all of which might be the actual target of natural selection. All in all, the phylogeographic and adaptive divergence studies indicate that most of the genetic divergence has occurred in the freshwater populations whereas the marine populations have remained relatively uniform.Tietoa lajin sisäisen geneettisen monimuotoisuuden jakautumisesta populaatioiden välillä ja DNA:n tasolla voidaan käyttää lajiutumiseen johtavien geneettisten muutosten tutkimiseen. Pohjoisen pallonpuoliskon kalalajit, kuten kolmipiikki (Gasterosteus aculeatus) ovat sopivia mallilajeja geneettisen monimuotoisuuden ja varhaisen lajiutumisen tutkimuksessa erityisesti ulkoasultaan erilaisten populaatioiden vuoksi. Tämän väitöstutkimuksen tarkoituksena oli selvittää kolmipiikin levinneisyyshistoriaa ja populaatiorakennetta molekyylituntomerkkien avulla. Lisäksi tutkimus kohdentui luonnonvalinnan kannalta merkityksellisien kromosomialueiden kartoitukseen. Mitokondriaalisen DNA:n valossa näyttää siltä, että kolmipiikki on saapunut Atlanttiin verraten hiljattain mutta on erilaistunut kolmeen evoluutiolinjaan; trans-Atlanttiseen, Eurooppalaiseen ja Mustan meren linjoihin. Tuman molekyylituntomerkit paljastivat järvi- ja jokipopulaatioiden saaneen alkunsa meressä elävistä kolmipiikeistä mutta makean veden populaatiot ovat seurausta monista itsenäisistä asuttamisista. Erilaistumisen aste Balkanin niemimaan populaatioissa oli sekä molekyylintuntomerkeissä ja morfologisessa muuntelussa huomattavasti suurempaa kuin muissa Eurooppalaisissa populaatioissa. Tämä tulos tukee Balkanin niemimaan populaatioiden asemaa evolutiivisesti merkittävinä yksiköinä, joiden erityisasema pitäisi ottaa lajin geneettisen monimuotoisuuden suojelussa. Kolmipiikkipopulaatioiden sopetuminen makeaan veteen johtaa usein muutoksiin niiden morfologisissa ominaisuksissa. Sekvenssimuuntelu geenissä, joka koodaa kylkilevyjen määrän muuntelua vahvisti aiemman globaalin tutkimuksen tulokset myös Fennoskandian populaatioissa. Täyden kylkilevymäärän alleeli esiintyi hyvin korkealla frekvensillä meripopulaatioissa kun taas alleeli, joka vastaa kylkilevymäärän vähenemisestä esiintyi yleisenä makean veden populaatioissa. Luonnonvalinnan signaalien etsimiseen perustunut genomin kartoitus paljasti useita genomialueita, joissa tasapainottava ja suuntaava valinta ovat todennäköisesti vaikuttaneet. Näissä molekyylituntomerkkeissä alleelifrekvenssit olivat joko epätavalisen samanalaiset tai erilaiset verrattuna koko genomin keskiarvoon. Tarkempi tutkimus genomialueella, jossa todettiin suuntaavan valinnan signaali, vahvisti että signaali on havaittavissa monessa molekyylituntomerkkilokuksessa. Tämä genomialue sisälsi kuitenkin useita ennustettuja geenejä, joten varmuudella ei pystytty selvittämään mikä geeni on luonnonvalinnan suosima. Tämän väitöskirjan tulosten valossa näyttää siltä, että suurin osa populaatioden välisistä geneettisistä eroista johtuu makean veden populaatioiden eroista kun taas meripopulaatiot ovat säilyneet melko samankaltaisina

Analysis of the structure of time-frequency information in electromagnetic brain signals

This thesis encompasses methodological developments and experimental work aimed at revealing information contained in time, frequency, and time–frequency representations of electromagnetic, specifically magnetoencephalographic, brain signals. The work can be divided into six endeavors. First, it was shown that sound slopes increasing in intensity from undetectable to audible elicit event-related responses (ERRs) that predict behavioral sound detection. This provides an opportunity to use non-invasive brain measures in hearing assessment. Second, the actively debated generation mechanism of ERRs was examined using novel analysis techniques, which showed that auditory stimulation did not result in phase reorganization of ongoing neural oscillations, and that processes additive to the oscillations accounted for the generation of ERRs. Third, the prerequisites for the use of continuous wavelet transform in the interrogation of event-related brain processes were established. Subsequently, it was found that auditory stimulation resulted in an intermittent dampening of ongoing oscillations. Fourth, information on the time–frequency structure of ERRs was used to reveal that, depending on measurement condition, amplitude differences in averaged ERRs were due to changes in temporal alignment or in amplitudes of the single-trial ERRs. Fifth, a method that exploits mutual information of spectral estimates obtained with several window lengths was introduced. It allows the removal of frequency-dependent noise slopes and the accentuation of spectral peaks. Finally, a two-dimensional statistical data representation was developed, wherein all frequency components of a signal are made directly comparable according to spectral distribution of their envelope modulations by using the fractal property of the wavelet transform. This representation reveals noise buried processes and describes their envelope behavior. These examinations provide for two general conjectures. The stability of structures, or the level of stationarity, in a signal determines the appropriate analysis method and can be used as a measure to reveal processes that may not be observable with other available analysis approaches. The results also indicate that transient neural activity, reflected in ERRs, is a viable means of representing information in the human brain.reviewe