Population Lifetime Research Articles

Reliable survival analysis based on the Dirichlet process.

We present a robust Dirichlet process for estimating survival functions from samples with right-censored data. It adopts a prior near-ignorance approach to avoid almost any assumption about the distribution of the population lifetimes, as well as the need of eliciting an infinite dimensional parameter (in case of lack of prior information), as it happens with the usual Dirichlet process prior. We show how such model can be used to derive robust inferences from right-censored lifetime data. Robustness is due to the identification of the decisions that are prior-dependent, and can be interpreted as an analysis of sensitivity with respect to the hypothetical inclusion of fictitious new samples in the data. In particular, we derive a nonparametric estimator of the survival probability and a hypothesis test about the probability that the lifetime of an individual from one population is shorter than the lifetime of an individual from another. We evaluate these ideas on simulated data and on the Australian AIDS survival dataset. The methods are publicly available through an easy-to-use R package.

Highly Selective Relaxation of the OH Stretching Overtones in Isolated HDO Molecules Observed by Infrared Pump-Repump-Probe Spectroscopy.

A quantitative investigation of the relaxation dynamics of higher-lying vibrational states is afforded by a novel method of infrared pump-repump-probe spectroscopy. The technique is used to study the dynamics of OH stretching overtones in NaClO4·HDO monohydrate. We observe a continuous decrease of the energy separation for the first four states, i.e. v01 = 3575 cm(-1), v12 = 3370 cm(-1), and v23 = 3170 cm(-1), respectively. The population lifetime of the first excited state is 7.2 ps, while the one of the second excited state is largely reduced to 1.4 ps. The relaxation of the v = 2 state proceeds nearly quantitatively to the v = 1 state. The new information on the OH stretching overtones demands improved theoretical potentials and modeling of the H bond interactions. This work shows the potential of the new technique for the precise study of complex vibrational relaxation pathways.

Inequivalence of Single-Particle and Population Lifetimes in a Cuprate Superconductor.

We study optimally doped Bi-2212 (T(c)=96 K) using femtosecond time- and angle-resolved photoelectron spectroscopy. Energy-resolved population lifetimes are extracted and compared with single-particle lifetimes measured by equilibrium photoemission. The population lifetimes deviate from the single-particle lifetimes in the low excitation limit by 1-2 orders of magnitude. Fundamental considerations of electron scattering unveil that these two lifetimes are in general distinct, yet for systems with only electron-phonon scattering they should converge in the low-temperature, low-fluence limit. The qualitative disparity in our data, even in this limit, suggests that scattering channels beyond electron-phonon interactions play a significant role in the electron dynamics of cuprate superconductors.

Characterization of Cs vapor cell coated with octadecyltrichlorosilane using coherent population trapping spectroscopy

We report the realization and characterization using coherent population trapping (CPT) spectroscopy of an octadecyltrichlorosilane (OTS)-coated centimeter-scale Cs vapor cell. The dual-structure of the resonance lineshape, with presence of a narrow structure line at the top of a Doppler-broadened structure, is clearly observed. The linewidth of the narrow resonance is compared to the linewidth of an evacuated Cs cell and of a buffer gas Cs cell of similar size. The Cs-OTS adsorption energy is measured to be (0.42 ± 0.03) eV, leading to a clock frequency shift rate of 2.7 × 10−9/K in fractional unit. A hyperfine population lifetime, T1, and a microwave coherence lifetime, T2, of 1.6 and 0.5 ms are reported, corresponding to about 37 and 12 useful bounces, respectively. Atomic-motion induced Ramsey narrowing of dark resonances is observed in Cs-OTS cells by reducing the optical beam diameter. Ramsey CPT fringes are detected using a pulsed CPT interrogation scheme. Potential applications of the Cs-OTS cell to the development of a vapor cell atomic clock are discussed.

Giant exciton oscillator strength and radiatively limited dephasing in two-dimensional platelets

We measured the intrinsic ground-state exciton dephasing and population dynamics in colloidal quasi two-dimensional (2D) CdSe nanoplatelets at low temperature (5-50K) using transient resonant four-wave mixing in heterodyne detection. Our results indicate that below 20K the exciton dephasing is lifetime limited, with the exciton population lifetime being as fast as 1ps. This is consistent with an exciton lifetime given by a fast radiative decay due to the large in-plane coherence area of the exciton center-of-mass motion in these quasi 2D systems compared to spherical nanocrystals.

Visual Height Intolerance and Acrophobia – Clinical Characteristics and Comorbidity Patterns

Objective The purpose of this study was to estimate the general population life-time and point prevalence of visual height intolerance and acrophobia, to define their clinical characteristics and to determine their anxious and depressive comorbidities. Method A case-control study was conducted within a German population-based cross-sectional telephone survey. A representative sample of 2,012 individuals aged 14 and above were selected. Defined neurological conditions (migraine, Meniere's disease, motion sickness), symptom pattern, age of first manifestation, precipitating height stimuli, course of illness, psychosocial impairment, and comorbidity patterns (anxiety conditions, depressive disorders according to DSM-IV-TR) for vHI and acrophobia were assessed. Results The life-time prevalence of vHI was 28.5% (women: 32.4%, men: 24.5%). Initial attacks occurred predominantly (36%) in the second decade. A rapid generalization to other height stimuli and a chronic course of illness with at least moderate impairment were observed. 22.5% of individuals with vHI experienced the intensity of panic attacks. The life-time prevalence of acrophobia was 6.4% (women: 8.6%, men: 4.1%), point prevalence was 2.0% (women: 2.8%; men: 1.1%). VHI and even more acrophobia were associated with high rates of comorbid anxious and depressive conditions. Migraine was both a significant predictor of later acrophobia and a significant consequence of previous acrophobia. Conclusions VHI affects nearly a third of the general population; in more than 20% of these persons vHI occasionally develops into panic attacks and in 6.4% it escalates to acrophobia. Symptoms and degree of social impairment form a continuum of mild to seriously distressing conditions in susceptible subjects.

A novel approach for identifying causal models of complex diseases from family data.

Causal models including genetic factors are important for understanding the presentation mechanisms of complex diseases. Familial aggregation and segregation analyses based on polygenic threshold models have been the primary approach to fitting genetic models to the family data of complex diseases. In the current study, an advanced approach to obtaining appropriate causal models for complex diseases based on the sufficient component cause (SCC) model involving combinations of traditional genetics principles was proposed. The probabilities for the entire population, i.e., normal-normal, normal-disease, and disease-disease, were considered for each model for the appropriate handling of common complex diseases. The causal model in the current study included the genetic effects from single genes involving epistasis, complementary gene interactions, gene-environment interactions, and environmental effects. Bayesian inference using a Markov chain Monte Carlo algorithm (MCMC) was used to assess of the proportions of each component for a given population lifetime incidence. This approach is flexible, allowing both common and rare variants within a gene and across multiple genes. An application to schizophrenia data confirmed the complexity of the causal factors. An analysis of diabetes data demonstrated that environmental factors and gene-environment interactions are the main causal factors for type II diabetes. The proposed method is effective and useful for identifying causal models, which can accelerate the development of efficient strategies for identifying causal factors of complex diseases.

Association study of the SLC6A3 VNTR (DAT) and DRD2/ANKK1 Taq1A polymorphisms with alcohol dependence in a population from northeastern Brazil.

Alcohol dependence (AD) is a complex psychiatric disorder, affecting 5.4% of the general population lifetime, characterized by excessive alcohol consumption influenced by environmental risk factors and genetic factors. Genetic alterations in dopaminergic system are involved in the treatment and etiology of AD. The aim of this search was to test the association of the SLC6A3 40bp-VNTR and DRD2/ANKK1 Taq1A single nucleotide polymorphism (SNP), a transporter and receptor of the dopaminergic system, with AD through a study in a population of northeastern Brazil. The study design was a case-control that included 227 males of northeastern Brazil (113 alcoholics and 114 controls). Alcoholics were classified according to the DSM-IV criteria for AD and controls were subjects who had nonalcohol problems or who never drank. Genotyping was detected through polymerase chain reaction (PCR) for SLC6A3 40bp-VNTR and RFLP-PCR for DRD2/ANKK1 Taq1A, and subsequent electrophoresis on a 2% agarose gel. The distribution of allele and genotype frequencies and association of polymorphisms with AD were assessed by chi-square, Fisher's exact test, and odds ratio (OR) with a confidence interval of 95% and significance p<0.05. Data were analyzed on BioEstat 5.3 software. The SLC6A3 40bp-VNTR was associated with AD, allelic, and genotypic frequencies were significantly different, respectively (A9 vs. A10: OR=1.88; p=0.01; A9/A9 vs. A10/A10: OR=6.25; p=0.02; A9/A9 vs. A9/A10+A10A10: OR=5.44; p=0.03). However, there was no statistically significant difference when the allelic (p=0.10) and genotypic (p>0.05) frequencies for DRD2/ANKK1 Taq1A were compared. These findings suggest that A9 allele and A9/A9 genotype of the SLC6A3 40bp-VNTR are involved in the vulnerability to AD in the population studied. However, for the DRD2/ANKK1 SNP does not present contributions to the development of AD.

How Do Group Ii Chaperonins Distinguish their Partially Folded Substrates from the Native States?

The features in partially folded intermediates that allow the group II chaperonins to distinguish partially folded from native states remain unclear. The Archaeal group II chaperonin Mm-Cpn assists the in vitro refolding of the well-characterized β-sheet lens protein human γD-Crystallin (HγD-Crys). The buried cores of this Greek key conformation as well as the domain interface includes a variety of side chains which might be exposed in partially folded intermediates. We sought to assess whether particular features buried in the native state, and thus absent from the native protein surface, might be serving as recognition signals. The features tested were a) paired aromatic side chains; b) side chains in the interface between the duplicated domains of HγD-Crys, and c) side chains in the buried core which result in congenital cataract when substituted. We tested the Mm-Cpn suppression of aggregation of HγD-Crys mutants of these residues, during refolding after dilution out of denaturant. Mm-Cpn was capable of suppressing the off-pathway aggregation of the three classes of mutant proteins indicating that the buried residues were not recognition signals. In fact Mm-Cpn refolded most mutant HγD-Crys to levels twice that of WT HγD-Crys. This presumably represents the increased population or longer lifetimes of the partially folded intermediates of the destabilized mutant proteins. The results suggest that Mm-Cpn does not recognize paired aromatic residues, exposed domain interface, or destabilized core - but rather recognizes other features of the partially folded β-sheet, such as an exposed backbone, that are absent or inaccessible in the native state off HγD-Crys. Supported by NIH EY15834 and EY016525.

Light storage in a room-temperature atomic vapor based on coherent population oscillations

We report the experimental observation of coherent population oscillation (CPO-) based light storage in an atomic vapor cell at room temperature. Using the ultranarrow CPO between the ground levels of a $\ensuremath{\Lambda}$ system selected by polarization in metastable $^{4}\mathrm{He}$, such a light storage is experimentally shown to be phase preserving. As it does not involve any atomic coherences it has the advantage of being robust to dephasing effects such as small magnetic field inhomogeneities. The storage time is limited by the population lifetime of the ground states of the $\ensuremath{\Lambda}$ system.

Tm 3+ Tm 3+ : Y3Ga5O12 materials for spectrally multiplexed quantum memories.

We investigate the relevant spectroscopic properties of the 795 nm (3)H(6)↔(3)H(4) transition in 1% Tm(3+):Y(3)Ga(5)O(12) at temperatures as low as 1.2 K for optical quantum memories based on persistent spectral tailoring of narrow absorption features. Our measurements reveal that this transition has uniform coherence properties over a 56 GHz bandwidth, and a simple hyperfine structure split by ± 44 MHz/T with lifetimes of up to hours. Furthermore, we find a (3)F(4) population lifetime of 64 ms-one of the longest lifetimes observed for an electronic level in a solid--and an exceptionally long coherence lifetime of 490 μs--the longest ever observed for optical transitions of Tm(3+) ions in a crystal. Our results suggest that this material allows realizing broadband quantum memories that enable spectrally multiplexed quantum repeaters.

Visual height intolerance and acrophobia: clinical characteristics and comorbidity patterns.

The purpose of this study was to estimate the general population lifetime and point prevalence of visual height intolerance and acrophobia, to define their clinical characteristics, and to determine their anxious and depressive comorbidities. A case-control study was conducted within a German population-based cross-sectional telephone survey. A representative sample of 2,012 individuals aged 14 and above was selected. Defined neurological conditions (migraine, Menière's disease, motion sickness), symptom pattern, age of first manifestation, precipitating height stimuli, course of illness, psychosocial impairment, and comorbidity patterns (anxiety conditions, depressive disorders according to DSM-IV-TR) for vHI and acrophobia were assessed. The lifetime prevalence of vHI was 28.5% (women 32.4%, men 24.5%). Initial attacks occurred predominantly (36%) in the second decade. A rapid generalization to other height stimuli and a chronic course of illness with at least moderate impairment were observed. A total of 22.5% of individuals with vHI experienced the intensity of panic attacks. The lifetime prevalence of acrophobia was 6.4% (women 8.6%, men 4.1%), and point prevalence was 2.0% (women 2.8%; men 1.1%). VHI and even more acrophobia were associated with high rates of comorbid anxious and depressive conditions. Migraine was both a significant predictor of later acrophobia and a significant consequence of previous acrophobia. VHI affects nearly a third of the general population; in more than 20% of these persons, vHI occasionally develops into panic attacks and in 6.4%, it escalates to acrophobia. Symptoms and degree of social impairment form a continuum of mild to seriously distressing conditions in susceptible subjects.

Increasing and decreasing the ultrastability of bacterial chemotaxis core signaling complexes by modifying protein-protein contacts.

The chemosensory signaling array of bacterial chemotaxis is composed of functional core units containing two receptor trimers of dimers, a homodimeric CheA kinase, and two CheW adaptor proteins. In vitro reconstitutions generate individual, functional core units and larger functional assemblies, including dimers, hexagons, and hexagonal arrays. Such reconstituted complexes have been shown to have both quasi-stable and ultrastable populations that decay with lifetimes of 1–2 days and ∼3 weeks at 22 °C, respectively, where decay results primarily from proteolysis of the bound kinase [Erbse, A. H., and Falke, J. J. (2009) Biochemistry 48, 6975–6987; Slivka, P. F., and Falke, J. J. (2012) Biochemistry 51, 10218–10228]. In this work, we show that the ultrastable population can be destabilized to the quasi-stable level via the introduction of a bulky tryptophan residue at either one of two essential protein–protein interfaces within the core unit: the receptor–kinase contact or kinase–adaptor interface 1. Moreover, we demonstrate that the quasi-stable population can be made ultrastable via the introduction of a disulfide bond that covalently stabilizes the latter interface. The resulting disulfide at least doubles the functional lifetime of the ultrastable population, to ≥5.9 weeks at 22 °C, by protecting the kinase from endogenous and exogenous proteases. Together, these results indicate that the ultrastability of reconstituted core complexes requires well-formed contacts among the receptor, kinase, and adaptor proteins, whereas quasi-stability arises from less perfect contacts that allow slow proteolysis of the bound kinase. Furthermore, the results reveal that ultrastability, and perhaps the size or order of chemosensory complexes and arrays, can be increased by an engineered disulfide bond that covalently cross-links a key interface. Overall, it appears that native ultrastability has evolved to provide an optimal rather than maximal level of kinetic durability, suggesting that altered selective pressure could either increase or decrease the functional lifetime of core complexes.

Deep Brain Stimulation in Major Depression: Plastic Changes of 5-Hydroxytryptamine Neurons

Major depressive disorder (MDD) is a severe psychiatric syndrome with a very high socioeconomic impact. The high cost of MDD is attributable to its large incidence in the general population (lifetime prevalence is close to 20%); the long duration of depressive episodes; and emergence of depressive episodes during active periods of adult life, which results in very large labor costs. The large and increasing impact of MDD is not paralleled by marked improvements in its treatment. The antidepressant market is dominated by drugs targeting the monoamine systems, such as selective serotonin reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors, which are pharmacologic refinements of tricyclic antidepressant drugs, which were discovered serendipitously in the 1950s. Selective serotonin reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors have increased treatment compliance because of the absence of severe side effects. However, their speed and efficacy are suboptimal, leaving a large percentage of patients with partial or incomplete responses after several months of treatment. Many patients are refractory to numerous pharmacologic treatments and require nonstandard interventions to improve their quality of life and reduce suicide risk. Antidepressant-like Effects of Cortical Deep Brain Stimulation Coincide With Pro-neuroplastic Adaptations of Serotonin SystemsBiological PsychiatryVol. 76Issue 3PreviewCortical deep brain stimulation (DBS) is a promising therapeutic option for treatment-refractory depression, but its mode of action remains enigmatic. Serotonin (5-HT) systems are engaged indirectly by ventromedial prefrontal cortex (vmPFC) DBS. Resulting neuroplastic changes in 5-HT systems could thus coincide with the long-term therapeutic activity of vmPFC DBS. Full-Text PDF ErratumBiological PsychiatryVol. 76Issue 5PreviewErratum to: “Deep Brain Stimulation in Major Depression: Plastic Changes of 5-Hydroxytryptamine Neurons” by Artigas which appeared in Biological Psychiatry (2014;76:174-175). On page 175, column 1, 8th line from the bottom, the findings were inadvertently misstated as a decrease rather than an increase. The full corrected sentence is: “Using this procedure, the authors found that CSDS induced a robust and significant increase of the density of 5-HT nerve endings in various forebrain areas, including the vmPFC, the basolateral amygdala, and the dentate gyrus of the hippocampal formation, which was normalized after long-term DBS treatment.” Full-Text PDF

Investigation of the solvent influence on polymer–fullerene solar cells by low frequency noise spectroscopy

The electron density of states and recombination kinetics of bulk heterojunction solar cells have been determined by means of low-frequency noise spectroscopy at room temperature and in dark conditions. The observed differences in the disorder parameter and electron lifetime are attributed to a different film ordering of the active layer because of the influence of a solvent additive. Blends prepared with the reference solvent resulted in the lowest electron lifetime and density of states population, while blends prepared with the addition of a high boiling point solvent resulted in a more efficient charge carrier separation and a higher electron lifetime.

NMR Studies on Transient Protein Complexes: Perspectives

It is generally understood that protein-protein interactions proceed via transient encounter complexes that rapidly evolve into the functional stereospecific complex. Direct detection and characterization of the encounter complexes, however, been difficult due to their low population and short lifetimes. Recent application of NMR paramagnetic relaxation enhancement first visualized the structures of the encounter complex ensemble, and allowed the characterization of their physicochemical properties. Further, rational protein mutations that perturbed the encounter complex formation provided a clue to the target search pathway during protein-protein association. Understanding the structure and dynamics of encounter complexes will provide useful information on the mechanism of protein association.

Coherence time extension inPr3+:Y2SiO5by self-optimized magnetic fields and dynamical decoupling

Long coherence times are an essential prerequisite for implementations of quantum information technology. This requires techniques to control perturbing processes and hence prolong coherence times in quantum systems. In our work, we present systematic experimental investigations on prolongation of spin coherence times in a rare-earth ion-doped crystal. The approach is based on a combination of established coherence control techniques (i.e., zero first-order Zeeman shifts and simple dynamical decoupling), supported by automatic optimization of experimental control parameters, as well as precise characterization of the optimization loop and the strongly modified complex level structure by spin echoes and high-resolution Raman heterodyne spectroscopy. The spin-echo and Raman heterodyne data clearly prove successful optimization towards proper conditions of zero first-order Zeeman shifts, finally yielding a coherence time of 1 min, i.e., close to the theoretical limit set by the population lifetime in ${\text{Pr}}^{3+}$:${\text{Y}}_{2}$${\text{SiO}}_{5}$.

CHEMICAL CONSTRAINTS ON THE CONTRIBUTION OF POPULATION III STARS TO COSMIC REIONIZATION

Recent studies have highlighted that galaxies at z = 6-8 fall short of producing enough ionizing photons to reionize the IGM, and suggest that Population III stars could resolve this tension, because their harder spectra can produce ~10x more ionizing photons than Population II. But this argument depends critically on the duration of the Population III era, and because Population III stars form from pristine gas, in turn depends on the rate of galactic enrichment. We use a semi-analytic model of galaxy formation which tracks galactic chemical evolution, to gauge the impact of Population III stars on reionization. Population III SNe produce distinct metal abundances, and we argue that the duration of the Population III era can be constrained by precise relative abundance measurements in high-z damped Ly{\alpha} absorbers (DLAs), which provide a chemical record of past star-formation. We find that a single generation of Population III stars can self-enrich galaxies above the critical metallicity Zcrit=10^-4 Zsun for the Population III-to-II transition, on a very short timescale of ~10^6 yr, owing to the large metal yields and short lifetimes of Population III stars. This subsequently terminates the Population III era, hence they contribute >~ 50% of the ionizing photons only for z >~ 30, and at z=10 contribute <1%. The Population III contribution can be increased by delaying metal mixing into the ISM. However comparing the resulting metal abundance pattern to existing measurements in z <~ 6 DLAs, we show that the fractional contribution of high-mass Population III stars to the ionization rate must be <~ 10% at z = 10. Future abundance measurements of z~7-8 QSOs and GRBs should probe the era when the chemical vestiges of Population III star formation become detectable.

Group II archaeal chaperonin recognition of partially folded human γD-crystallin mutants

The features in partially folded intermediates that allow the group II chaperonins to distinguish partially folded from native states remain unclear. The archaeal group II chaperonin from Methanococcus Mauripaludis (Mm-Cpn) assists the in vitro refolding of the well-characterized β-sheet lens protein human γD-crystallin (HγD-Crys). The domain interface and buried cores of this Greek key conformation include side chains, which might be exposed in partially folded intermediates. We sought to assess whether particular features buried in the native state, but absent from the native protein surface, might serve as recognition signals. The features tested were (a) paired aromatic side chains, (b) side chains in the interface between the duplicated domains of HγD-Crys, and (c) side chains in the buried core which result in congenital cataract when substituted. We tested the Mm-Cpn suppression of aggregation of these HγD-Crys mutants upon dilution out of denaturant. Mm-Cpn was capable of suppressing the off-pathway aggregation of the three classes of mutants indicating that the buried residues were not recognition signals. In fact, Mm-Cpn recognized the HγD-Crys mutants better than (wild-type) WT and refolded most mutant HγD-Crys to levels twice that of WT HγD-Crys. This presumably represents the increased population or longer lifetimes of the partially folded intermediates of the mutant proteins. The results suggest that Mm-Cpn does not recognize the features of HγD-Crys tested-paired aromatics, exposed domain interface, or destabilized core-but rather recognizes other features of the partially folded β-sheet conformation that are absent or inaccessible in the native state of HγD-Crys.

Prevalence of Gambling Problems Among the Clients of a Toronto Homeless Shelter

Few studies have examined the prevalence of problem and pathological gambling among clients of homeless service agencies. The objective of this study was to estimate the prevalence of problem gambling among these clients. We collected primary data on gambling using the NORC diagnostic screen for disorders. Using a modified time-location recruitment approach 264 clients of a community homeless service agency were screened for lifetime gambling problems. Descriptive statistics were produced using SPSSX. The prevalence of lifetime problem gambling was 10 % and that of pathological gambling was 25 % in this sample. The prevalence of lifetime problem and pathological gambling was alarmingly high relative to the general population lifetime prevalence. Better insight into interventions for gambling that might reduce risk of homelessness will help service agencies gauge the needs of their clients and to implement change to service delivery and screening practices.