Dynamic instabilities in scalar neural field equations with space-dependent delays

In this paper we consider a class of scalar integral equations with a form of space-dependent delay. These non-local models arise naturally when modelling neural tissue with active axons and passive dendrites. Such systems are known to support a dynamic (oscillatory) Turing instability of the homogeneous steady state. In this paper we develop a weakly nonlinear analysis of the travelling and standing waves that form beyond the point of instability. The appropriate amplitude equations are found to be the coupled mean-field Ginzburg-Landau equations describing a Turing-Hopf bifurcation with modulation group velocity of O(1). Importantly we are able to obtain the coefficients of terms in the amplitude equations in terms of integral transforms of the spatio-temporal kernels defining the neural field equation of interest. Indeed our results cover not only models with axonal or dendritic delays but those which are described by a more general distribution of delayed spatio-temporal interactions. We illustrate the predictive power of this form of analysis with comparison against direct numerical simulations, paying particular attention to the competition between standing and travelling waves and the onset of Benjamin-Feir instabilities.

Contactless Spectral-Dependent Measurement of Bulk Lifetime and Surface Recombination Velocity in Silicon Photovoltaic Materials

Charge carrier lifetime measurements in bulk or unfinished photovoltaic (PV) materials allow for a more accurate estimate of power conversion efficiency in completed solar cells. In this work, carrier lifetimes in PV- grade silicon wafers are obtained by way of quasi-steady state photoconductance measurements. These measurements use a contactless RF system coupled with varying narrow spectrum input LEDs, ranging in wavelength from 460 nm to 1030 nm. Spectral dependent lifetime measurements allow for determination of bulk and surface properties of the material, including the intrinsic bulk lifetime and the surface recombination velocity. The effective lifetimes are fit to an analytical physics-based model to determine the desired parameters. Passivated and non-passivated samples are both studied and are shown to have good agreement with the theoretical model.

Mechanism of pH-dependent activation of the sodium-proton antiporter NhaA

Data files to accompany the article in Nature Communications, in press.

ENZYME-FREE UBIQUITIN LIGATION. FROM NATIVE CHEMICAL LIGATION AND SPIN LABELING TO DIMERIZATION BY INTER-UBIQUITIN MIMICKING LINKAGE AND PH-DEPENDENT CONFORMATIONAL SWITCH

The delicate balance between the production and disposal of proteins is vital for the changes required in the cell to respond to given stimulus. Ubiquitination is a protein modification with a range of signaling outcomes when ubiquitin is attached to a protein through a highly ordered enzymatic cascade process. Understanding ubiquitination is a growing field and nowadays the application of chemical reactions allows the isolation of quantitative materials for structural studies. Therefore, in this dissertation it is described some of these suitable chemical methodologies to produce an isopeptide bond toward the polymerization of ubiquitin bypassing the enzymatic control with the purpose of showing if these chemical modifications have a direct impact on the structure of ubiquitin. First, the possibility of incorporating non-natural lysine analogs known as mercaptolysines into the polypeptide chain of Ubiquitin was explored when they were attached to ubiquitin by native chemical ligation at its C terminus. The sulfhydryl group was used for the attachment of a paramagnetic label to map the surface of ubiquitin. Second, the condensation catalyzed by silver nitrate was used for the dimer assembly. In particular, the main focus was on examining whether orthogonal protection and deprotection of each monomer have an impact on the reaction yield, since the synthetic strategy has been previously attempted successfully. Third, the formation of ubiquitin dimers was approached by building an inter-ubiquitin linkage mimicking the isopeptide bond with two approaches, the classic disulfide exchange as well as the thiol-ene click reaction by thermal initiation in aqueous conditions. After assembling the dimeric units, they were studied by Nuclear Magnetic Resonance, in order to establish a conformational state profile which depends on the pH conditions. The latter is a very important concept since some ligands have a preferred affinity when the protein-protein hydrophobic patches are in close proximity.

Analysis and control of transient spectra using time-dependent density functional theory.

215 p.

Feasibility of resting-state microstates neurofeedback

Despite major progress, currently available treatment options for patients suffering from schizophrenia remain suboptimal. Antipsychotic medication is one such option, and is helpful in acute phases of the disease. However, antipsychotics cause significant side-effects that often require additional medication, and can even trigger the discontinuation of treatment. Taken together, along with the fact that 20-30% of patients are medication-resistant, it is clear that new medical care options should be developed for patients with schizophrenia. Besides medication, an emerging option to treat psychiatric symptoms is through the use of neurofeedback. This technique has proven efficacy for other disorders and, more importantly, has also proven to be feasible in patients with schizophrenia. One of the major advantages of this approach is that it allows for the influence of brain states that otherwise would be inaccessible; i.e. the physiological markers underlying psychotic symptoms. EEG resting-state microstates are a very interesting electrophysiological marker of schizophrenia symptoms. Precisely, a specific class of resting-state microstates, namely microstate class D, has consistently been found to show a temporal shortening in patients with schizophrenia compared to controls, and this shortening is correlated with the presence positive psychotic symptoms. Under the scope of biological psychiatry, appropriate treatment of psychotic symptoms can be expected to modify the underlying physiological markers accompanying behavioral manifestations of a disease. We reason that if abnormal temporal parameters of resting-state microstates seem to be related to positive symptoms in schizophrenia, regulating this EEG feature might be helpful as a treatment for patients. The goal of this thesis was to prove the feasibility of microstate class D contribution self-regulation via neurofeedback. Given that no other study has attempted to regulate microstates via neurofeedback, we first tested its feasibility in a population of healthy subjects. In the first paper we describe the methodological characteristics of the neurofeedback protocol and its implementation. Neurofeedback performance was assessed by means of linear mixed effects modeling, which provided a complete profile of the neurofeedback’s training response within and between-subjects. The protocol included 20 training sessions, and each session contained three conditions: baseline (resting-state) and two active conditions: training (auditory feedback upon self-regulation performance) and transfer (self-regulation with no feedback). With linear modeling we obtained performance indices for each of them as follows: baseline carryover (baseline increments time-dependent) and learning and aptitude for each of the active conditions. Learning refers to the increase/decrease of the microstate class D contribution, time-dependent during each active condition, and aptitude refers to the constant difference of the microstate class D contribution between each active condition and baseline independent of time. The indices provided are discussed in terms of tailoring neurofeedback treatment to individual profiles so that it can be applied in future studies or clinical practice. In our sample of participants, neurofeedback proved feasible, as all participants at least showed positive results in one of the aforementioned learning indices. Furthermore, between-subjects we observed that the contribution of microstate class D across-sessions increased by 0.42% during baseline, 1.93% during training trials, and 1.83% during transfer. This range is expected to be effective in treating psychotic symptoms in patients. In the second paper presented in this thesis, we explored the possible predictors of neurofeedback success among psychological variables measured with questionnaires. An interesting finding was the negative correlation between “motivational incongruence” and some of the neurofeedback performance indices. Even though this finding requires replication, we discuss it in terms of the interfering effects of incompatible psychological processes with neurofeedback training requirements. In the third paper, we present a meta-analysis on all available studies that have related resting-state microstate abnormalities and schizophrenia. We obtained medium effect sizes for two microstate classes, namely C and D. Combining the meta-analysis results with the fact that microstate class D abnormalities are correlated with the presence of positive symptoms in patients with schizophrenia, these results add further support for the training of this precise microstate. Overall, the results obtained in this study encourage the implementation of this protocol in a population of patients with schizophrenia. However, future studies will have to show whether patients will be able to successfully self-regulate the contribution of microstate class D and, if so, whether this regulation will have an impact on symptomatology.

Hazard Mitigation Element Quality in Coastal Comprehensive Plans in a State with Strong Requirements for Hazard Mitigation Plan Elements

This dissertation examines the quality of hazard mitigation elements in a coastal, hazard prone state. I answer two questions. First, in a state with a strong mandate for hazard mitigation elements in comprehensive plans, does plan quality differ among county governments? Second, if such variation exists, what drives this variation? My research focuses primarily on Florida’s 35 coastal counties, which are all at risk for hurricane and flood hazards, and all fall under Florida’s mandate to have a comprehensive plan that includes a hazard mitigation element. Research methods included document review to rate the hazard mitigation elements of all 35 coastal county plans and subsequent analysis against demographic and hazard history factors. Following this, I conducted an electronic, nationwide survey of planning professionals and academics, informed by interviews of planning leaders in Florida counties. I found that hazard mitigation element quality varied widely among the 35 Florida coastal counties, but were close to a normal distribution. No plans were of exceptionally high quality. Overall, historical hazard effects did not correlate with hazard mitigation element quality, but some demographic variables that are associated with urban populations did. The variance in hazard mitigation element quality indicates that while state law may mandate, and even prescribe, hazard mitigation in local comprehensive plans, not all plans will result in equal, or even adequate, protection for people. Furthermore, the mixed correlations with demographic variables representing social and disaster vulnerability shows that, at least at the county level, vulnerability to hazards does not have a strong effect on hazard mitigation element quality. From a theory perspective, my research is significant because it compares assumptions about vulnerability based on hazard history and demographics to plan quality. The only vulnerability-related variables that appeared to correlate, and at that mildly so, with hazard mitigation element quality, were those typically representing more urban areas. In terms of the theory of Neo-Institutionalism and theories related to learning organizations, my research shows that planning departments appear to have set norms and rules of operating that preclude both significant public involvement and learning from prior hazard events.

Roster of State Officials, 2007

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.

Roster of State Officials, 2001

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.

Roster of State Officials, 2000

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.

Roster of State Officials, 1999

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.

Roster of State Officials, 1998

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.

Roster of State Officials, 1996

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.

Roster of State Officials, 1995

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.

Roster of State Officials, 1994

Pursuant to Iowa Code section 2B.5, the State Roster is published as a correct list of state officers and deputies, members of boards and commissions, justices of the Supreme Court, judges of the Court of Appeals, judges of the district courts, including district associate judges and judicial magistrates, and members of the General Assembly. More specifically, the State Roster lists the membership of active, policy-making boards and commissions established by state law, executive order of the Governor, or Iowa Court Rule. The State Roster may also list advisory councils of a permanent nature whose members are appointed by the Governor, as well as other boards and commissions of interest to the public.