Dynamic information aggregation in asset prices

This thesis investigates how the information dispersed among market participants dynamically aggregates in asset prices, the extent to which prices reflect available information, and how such information affects investors’ decisions. The main model considers a population of investors with different absolute risk aversions and time-varying, diverse signals on the growth rate of an asset’s dividends. Each investor bids the asset based on the information in his private signal and in the asset price itself, which is determined in equilibrium by the market-clearing condition and partially reflects the signals of other market participants. The dividend stream is driven by a latent variable, which investors strive to estimate based on their individual, private information, and on the common knowledge revealed by prices. We find in closed form equilibrium prices and the optimal behaviour of the agents. Price volatility depends on the volatility of dividends and on the volatility of the estimate of the latent variable, which is revealed to all agents through prices. Equilibrium prices do not reveal all the private signals of market participants, but the same estimate of the state of the economy that an agent with all private signals would be able to obtain. Put differently, prices reveal not all information but all relevant information. The first chapter presents a baseline model, where the only noise in the market is on the stochastic dividend process. In the second chapter dividends become mean reverting to a state variable observed by all agents - the state of the economy - which fluctuates over time. The state of the economy is unobservable in the last chapter, but market participants have individual information, which jointly with asset prices, helps them to estimate the latent variable

Two Asian egg parasitoids of Halyomorpha halys (Stål) (Hemiptera, Pentatomidae) emerge in northern Italy: Trissolcus mitsukurii (Ashmead) and Trissolcus japonicus (Ashmead) (Hymenoptera, Scelionidae)

Halyomorpha halys (Stål) is a severe agricultural pest that is spreading worldwide from its original distribution in Asia. Egg parasitoids from Asia, which play a key role in the population dynamics of H. halys, are following its host along global pathways. We present the first records of Trissolcus mitsukurii in Europe, and of Trissolcus japonicus in Italy. Both discoveries were made in northern Italy, where H. halys is widely present and has reached extremely high population densities in some areas. Given the availability of their host, the distributions and populations of these exotic egg parasitoids are expected to expand, even in the absence of human intervention

Association between Protective and Deleterious HLA Alleles with Multiple Sclerosis in Central East Sardinia

The human leukocyte antigen (HLA) complex on chromosome 6p21 has been unambiguously associated with multiple sclerosis (MS). The complex features of the HLA region, especially its high genic content, extreme polymorphism, and extensive linkage disequilibrium, has prevented to resolve the nature of HLA association in MS. We performed a family based association study on the isolated population of the Nuoro province (Sardinia) to clarify the role of HLA genes in MS. The main stage of our study involved an analysis of the ancestral haplotypes A2Cw7B58DR2DQ1 and A30Cw5B18DR3DQ2. On the basis of a multiplicative model, the effect of the first haplotype is protective with an odds ratio (OR) = 0.27 (95% confidence interval CI 0.13–0.57), while that of the second is deleterious, OR 1.78 (95% CI 1.26–2.50). We found both class I (A, Cw, B) and class II (DR, DQ) loci to have an effect on MS susceptibility, but we saw that they act independently from each other. We also performed an exploratory analysis on a set of 796 SNPs in the same HLA region. Our study supports the claim that Class I and Class II loci act independently on MS susceptibility and this has a biological explanation. Also, the analysis of SNPs suggests that there are other HLA genes involved in MS, but replication is needed. This opens up new perspective on the study of MS

Dynamic information aggregation in asset prices

This thesis investigates how the information dispersed among market participants dynamically aggregates in asset prices, the extent to which prices reflect available information, and how such information affects investors’ decisions. The main model considers a population of investors with different absolute risk aversions and time-varying, diverse signals on the growth rate of an asset’s dividends. Each investor bids the asset based on the information in his private signal and in the asset price itself, which is determined in equilibrium by the market-clearing condition and partially reflects the signals of other market participants. The dividend stream is driven by a latent variable, which investors strive to estimate based on their individual, private information, and on the common knowledge revealed by prices. We find in closed form equilibrium prices and the optimal behaviour of the agents. Price volatility depends on the volatility of dividends and on the volatility of the estimate of the latent variable, which is revealed to all agents through prices. Equilibrium prices do not reveal all the private signals of market participants, but the same estimate of the state of the economy that an agent with all private signals would be able to obtain. Put differently, prices reveal not all information but all relevant information. The first chapter presents a baseline model, where the only noise in the market is on the stochastic dividend process. In the second chapter dividends become mean reverting to a state variable observed by all agents - the state of the economy - which fluctuates over time. The state of the economy is unobservable in the last chapter, but market participants have individual information, which jointly with asset prices, helps them to estimate the latent variable

Informational efficiency and welfare

In a continuous-time market with a safe rate and a risky asset that pays a dividend stream depending on a latent state of the economy, several agents make consumption and investment decisions based on public information–prices and dividends–and private signals. If eachinvestor has constant absolute risk aversion, equilibrium prices do not reveal all the privatesignals, but lead to the same estimate of the state of the economy that one would hypothetically obtain from the knowledge of all private signals. Accurate information leads to low volatility, ostensibly improving market efficiency, but also reduces each agent’s consumption through a decrease in the price of risk. Thus, informational efficiency is reached at the expense of agents’ welfare.</p

Hemiptera: Pentatomidae) in Western Slovenia

Halyomorpha halys (Hemiptera: Pentatomidae), native to East Asia, has become a globally invasive pest, as a serious threat to agricultural production and a notorious nuisance pest in urban areas. Considerable efforts have been made so far to develop effective pest control measures to prevent crop damage. Biological control of this invasive stink bug by egg parasitoids has proven to be the most environmentally sustainable long-term solution. Knowledge of the native egg parasitoid fauna is of key importance when implementing a biological control program. Therefore, the main objective of our study was to detect egg parasitoid species associated with H. halys in the Goriška region (Western Slovenia) and to evaluate their impact on the pest population under field conditions. In the years 2019 and 2020, around 4600 H. halys eggs were collected in the wild and more than 3400 sentinel eggs were exposed to detect parasitoids in the field. Five egg-parasitoid species emerged from H. halys eggs: Anastatus bifasciatus (Hymenoptera: Eupelmidae), Telenomus sp., Trissolcus basalis, Trissolcus mitsukurii (Hymenoptera: Scelionidae) and Ooencyrtus telenomicida (Hymenoptera: Encyrtidae), all of them are new records for Slovenia. The native species, An. bifasciatus, dominated in urban and suburban areas, while non-native Tr. mitsukurii prevailed in agricultural areas. Overall parasitism rates of naturally laid eggs by the parasitoid species complex in 2019 and 2020 was 3.0 and 14.4%, respectively. Rapid recruitment of native parasitoids, early detection of an effective alien parasitoid species and increasing overall parasitism rates are very encouraging results, which need to be followed and verified in future research

Magnetic Resonance Imaging and Its Effects on Metallic Brackets and Wires: Does It Alter the Temperature and Bonding Efficacy of Orthodontic Devices?

Magnetic resonance imaging (MRI) is a widely used diagnostic technique. Patients wearing orthodontic appliances are often requested to remove their appliances, even when the MRI exam involves anatomical areas far from mouth, in order to avoid heating of the metal and detachment of the appliance. The purpose of the present investigation was to measure and compare temperature changes and orthodontic appliances' adhesion to enamel after different MRIs. A total of 220 orthodontic brackets were bonded on bovine incisors and wires with different materials (stainless steel and nickel titanium). Moreover, various sizes (0.014″ and 0.019″ × 0.025″) were engaged. Appliances were submitted to MRI at two different powers (1.5 T and 3 T). The temperatures of brackets and wires were measured before and after MRI. Subsequently, the shear bond strength (SBS) and adhesive remnant index (ARI) scores were recorded. Statistical analysis was performed. After MRI, a significant increase in the temperature was found for both the brackets and wires in some groups, even if the mean temperature increase was clinically insignificant, as the temperature ranged between 0.05 °C and 2.4 °C for brackets and between 0.42 °C and 1.74 °C for wires. The MRI did not condition bracket adhesion in any group. No differences were reported when comparing the 1.5 T with 3 T groups. The ARI Scores were also significantly lower after MRI. The results of the present report show that, under MRI, orthodontic appliances present a low temperature rise and no debonding risk. Therefore, the removal of orthodontic appliance is not recommended routinely, but is suggested only in the case of a void risk or potential interference in image quality