Showing papers by "University of North Texas published in 2007"

Bone structure and formation: A new perspective

Abstract: Bone is a hierarchically structured composite material which, in addition to its obvious biological value, has been well studied by the materials engineering community because of its unique structure and mechanical properties. This article will review the existing bone literature, with emphasis on the prevailing theories regarding bone formation and structure, which lay the groundwork for proposing a new model to explain how intrafibrillar mineralization of collagen can be achieved during bone formation. Intrafibrillar refers to the fact that growth of the mineral phase is somehow directed by the collagen matrix, which leads to a nanostructured architecture consisting of uniaxially oriented nanocrystals of hydroxyapatite embedded within and roughly [0 0 1] aligned parallel to the long collagen fibril axes. Secondary (osteonal) bone, the focus of this review, is a laminated organic–inorganic composite composed primarily of collagen, hydroxyapatite, and water; but minor constituents, such as non-collagenous proteins (NCPs), are also present and are thought to play an important role in bone formation. To date, there has been no clear understanding of the role of these NCPs, although it has been generally assumed that the NCPs regulate solution crystal growth via some type of ‘epitaxial’ relationship between specific crystallographic faces and specific protein conformers. Indeed, ‘epitaxial’ relationships have been calculated; but in practice, it has not been demonstrated that intrafibrillar mineralization can be accomplished via this route. Because of the difficulty in examining biomineralization processes in vivo , the authors of this article have turned to using in vitro model systems to investigate the possible physicochemical mechanisms that may be involved in biomineralization. In the case of bone biomineral, we have now been able to duplicate the most fundamental level of bone structure, the interpenetrating nanostructured architecture, using relatively simple anionic polypeptides that mimic the polyanionic character of the NCPs. We propose that the charged polymer acts as a process-directing agent, by which the conventional solution crystallization is converted into a precursor process. This polymer-induced liquid-precursor (PILP) process generates an amorphous liquid-phase mineral precursor to hydroxyapatite which facilitates intrafibrillar mineralization of type-I collagen because the fluidic character of the amorphous precursor phase enables it to be drawn into the nanoscopic gaps and grooves of collagen fibrils by capillary action. The precursor then solidifies and crystallizes upon loss of hydration waters into the more thermodynamically stable phase, leaving the collagen fibrils embedded with nanoscopic hydroxyapatite (HA) crystals. Electron diffraction patterns of the highly mineralized collagen fibrils are nearly identical to those of natural bone, indicating that the HA crystallites are preferentially aligned with [0 0 1] orientation along the collagen fibril axes. In addition, studies of etched samples of natural bone and our mineralized collagen suggest that the long accepted “deck of cards” model of bone's nanostructured architecture is not entirely accurate. Most importantly, this in vitro model demonstrates that a highly specific, epitaxial-type interaction with NCPs is not needed to stimulate crystal nucleation and regulate crystal orientation, as has long been assumed. Instead, we propose that collagen is the primary template for crystal organization, but with the important caveat that this templating occurs only for crystals formed from an infiltrated amorphous precursor. These results suggest that the 25-year-old debate regarding bone formation via an amorphous precursor phase needs to be revisited. From a biomedical perspective, in addition to providing possible insight into the role of NCPs in bone formation, this in vitro system may pave the way toward the ultimate goal of fabricating a synthetic bone substitute that not only has a composition similar to bone, but has comparable mechanical properties and bioresorptive potential as natural bone. From a materials chemistry perspective, the non-specificity of the PILP process and capillary infiltration mechanism suggests that non-biological materials could also be fabricated into nanostructured composites using this “biomimetic” strategy.

Wikify!: linking documents to encyclopedic knowledge

Abstract: This paper introduces the use of Wikipedia as a resource for automatic keyword extraction and word sense disambiguation, and shows how this online encyclopedia can be used to achieve state-of-the-art results on both these tasks. The paper also shows how the two methods can be combined into a system able to automatically enrich a text with links to encyclopedic knowledge. Given an input document, the system identifies the important concepts in the text and automatically links these concepts to the corresponding Wikipedia pages. Evaluations of the system show that the automatic annotations are reliable and hardly distinguishable from manual annotations.

SemEval-2007 Task 14: Affective Text

Abstract: The "Affective Text" task focuses on the classification of emotions and valence (positive/negative polarity) in news headlines, and is meant as an exploration of the connection between emotions and lexical semantics. In this paper, we describe the data set used in the evaluation and the results obtained by the participating systems.

Comorbidity of chronic insomnia with medical problems.

Abstract: Study Objectives: Determine the comorbidity of insomnia with medical problems. Design: Cross-sectional and retrospective. Participants: Community-based population of 772 men and women, aged 20 to 98 years old. Measurements: Self-report measures of sleep, health, depression, and anxiety. Results: People with chronic insomnia reported more of the following than did people without insomnia: heart disease (21.9% vs 9.5%), high blood pressure (43.1% vs 18.7%), neurologic disease (7.3% vs 1.2%), breathing problems (24.8% vs 5.7%), urinary problems (19.7% vs 9.5%), chronic pain (50.4% vs 18.2%), and gastrointestinal problems (33.6% vs 9.2%). Conversely, people with the following medical problems reported more chronic insomnia than did those without those medical problems: heart disease (44.1% vs 22.8%), cancer (41.4% vs 24.6%), high blood pressure (44.0% vs 19.3%), neurologic disease (66.7% vs 24.3%), breathing problems (59.6% vs 21.4%), urinary problems (41.5% vs 23.3%), chronic pain (48.6% vs 17.2%), and gastrointestinal problems (55.4% vs 20.0%). When all medical problems were considered together, only patients with high blood pressure, breathing problems, urinary problems, chronic pain, and gastrointestinal problems continued to have statistically higher levels of insomnia than those without these medical disorders. Conclusion: This study demonstrates significant overlap between insomnia and multiple medical problems. Some research has shown it is possible to treat insomnia that is comorbid with select psychiatric (depression) and medical (eg, pain and cancer) disorders, which in turn increases the quality of life and functioning of these patients. The efficacy of treating insomnia in many of the above comorbid disorders has not been tested, indicating a need for future treatment research.

Cardiorespiratory Fitness and Adiposity as Mortality Predictors in Older Adults

Abstract: ContextAlthough levels of physical activity and aerobic capacity decline with age and the prevalence of obesity tends to increase with age, the independent and joint associations among fitness, adiposity, and mortality in older adults have not been adequately examined.ObjectiveTo determine the association among cardiorespiratory fitness (“fitness”), adiposity, and mortality in older adults.Design, Setting, and PatientsCohort of 2603 adults aged 60 years or older (mean age, 64.4 [SD, 4.8] years; 19.8% women) enrolled in the Aerobics Center Longitudinal Study who completed a baseline health examination during 1979-2001. Fitness was assessed by a maximal exercise test, and adiposity was assessed by body mass index (BMI), waist circumference, and percent body fat. Low fitness was defined as the lowest fifth of the sex-specific distribution of maximal treadmill exercise test duration. The distributions of BMI, waist circumference, and percent body fat were grouped for analysis according to clinical guidelines.Main Outcome MeasureAll-cause mortality through December 31, 2003.ResultsThere were 450 deaths during a mean follow-up of 12 years and 31 236 person-years of exposure. Death rates per 1000 person-years, adjusted for age, sex, and examination year were 13.9, 13.3, 18.3, and 31.8 across BMI groups of 18.5-24.9, 25.0-29.9, 30.0-34.9, and ≥35.0, respectively (P = .01 for trend); 13.3 and 18.2 for normal and high waist circumference (≥88 cm in women; ≥102 cm in men) (P = .004); 13.7 and 14.6 for normal and high percent body fat (≥30% in women; ≥25% in men) (P = .51); and 32.6, 16.6, 12.8, 12.3, and 8.1 across incremental fifths of fitness (P < .001 for trend). The association between waist circumference and mortality persisted after further adjustment for smoking, baseline health status, and BMI (P = .02) but not after additional adjustment for fitness (P = .86). Fitness predicted mortality risk after further adjustment for smoking, baseline health, and either BMI, waist circumference, or percent body fat (P < .001 for trend).ConclusionsIn this study population, fitness was a significant mortality predictor in older adults, independent of overall or abdominal adiposity. Clinicians should consider the importance of preserving functional capacity by recommending regular physical activity for older individuals, normal-weight and overweight alike.

Evacuation Decision Making and Behavioral Responses: Individual and Household

Abstract: Researchers have examined a wide range of factors that affect evacuation decisions after people hear hurricane forecasts and other information. This review of the literature focuses on three broad areas of research that often overlap: warning, risk perception, and evacuation research. Whereas it is challenging to demarcate the literature along these lines, we believe each of these areas represents important dimensions of evacuation decision making. The literature on warning focuses to varying degrees on warning as a social process, rather than a simple result of hearing official warnings. Warnings by themselves do not motivate evacuation — people must perceive risk. The extensive literature on objective and subjective processes in risk perception has to be evaluated. The review concludes with a focus on some important work in modeling evacuation and evacuation decision-making. Finally, we present recommendations for future research that draws on the strength of earlier work while focusing more directly on risk, the information included in hurricane forecasts, and the timing of those forecasts.

Postcranial evidence from early Homo from Dmanisi, Georgia

Abstract: The Plio-Pleistocene site of Dmanisi, Georgia, has yielded a rich fossil and archaeological record documenting an early presence of the genus Homo outside Africa. Although the craniomandibular morphology of early Homo is well known as a result of finds from Dmanisi and African localities, data about its postcranial morphology are still relatively scarce. Here we describe newly excavated postcranial material from Dmanisi comprising a partial skeleton of an adolescent individual, associated with skull D2700/D2735, and the remains from three adult individuals. This material shows that the postcranial anatomy of the Dmanisi hominins has a surprising mosaic of primitive and derived features. The primitive features include a small body size, a low encephalization quotient and absence of humeral torsion; the derived features include modern-human-like body proportions and lower limb morphology indicative of the capability for long-distance travel. Thus, the earliest known hominins to have lived outside of Africa in the temperate zones of Eurasia did not yet display the full set of derived skeletal features.

Learning Multilingual Subjective Language via Cross-Lingual Projections

Abstract: This paper discusses learning multilingual subjective language via cross-lingual projections.

Translocation of C60 and its derivatives across a lipid bilayer.

Abstract: Obtaining an understanding, at the atomic level, of the interaction of nanomaterials with biological systems has recently become an issue of great research interest. Here we report on the molecular dynamics study of the translocation of fullerene C60 and its derivative C60(OH)20 across a model cell membrane (dipalmitoylphosphatidylcholine or DPPC bilayer). The simulation results indicate that, although a pristine C60 molecule can readily "jump" into the bilayer and translocate the membrane within a few milliseconds, the C60(OH)20 molecule can barely penetrate the bilayer. Indeed, the mean translocation time via diffusion for the C60(OH)20 molecule is several orders of magnitude longer than for the former. It was also determined that the two different forms of fullerenes, when adsorbed into/onto the bilayer, affected the membrane structure differently. This study offers a mechanistic explanation of that difference and for the reduced acute toxicity of functionalized fullerenes.

Fabrication of Monodisperse Gel Shells and Functional Microgels in Microfluidic Devices

Abstract: Microgels are colloidal gel particles that consist of chemically cross-linked three-dimensional polymer networks; these networks are able to dramatically shrink or swell by expelling or absorbing large amounts of water in response to external stimuli. 2] The large change in size can be achieved, for example, by modifying the pH, temperature, or ionic strength of the medium, or by applying electric or magnetic fields; it is this response that makes microgels desirable for applications in drug delivery, biosensing, diagnostics, bioseparations, and optical devices. 10] To further expand their range of applicability, there have been efforts to generate microgels that have been complexed with preformed functionalized materials that impart additional desirable properties to the microgel. These preformed materials range from molecules to microparticles and are typically complexed with the gel matrix through specific interactions. The resulting complexed microgels usually show a drastic decrease in their physical response to external stimuli compared to that of the original cross-linked polymer networks; this is an undesirable side effect since the microgel performance for a given application is based on its sensitivity to external stimuli. In addition to functionality, the size distribution of a population of microgels is important; it is critical to provide a homogeneous distribution of microgels applying formulations and in controlling the release kinetics of encapsulates or adsorbents. From the standpoint of performance and applicability, there is a need for methods to generate monodisperse microgels that maintain high sensitivity to external stimuli irrespective of the materials that are incorporated to add complementary functions. Here, we describe a flexible and straightforward method for generating monodisperse suspensions of new microgelbased materials using a capillary microfluidic technique. This technique enabled us to generate and precisely control the size of the microgel-based particles without sacrificing the physical response of the resulting microgels. We generated two novel microgel structures: a spherical microgel shell and spherical microgel particles that retain their full sensitivity to external stimuli after being physically complexed with preformed colloidal particles. The overall size and thickness of the microgel shells can be tuned with temperature. We generated the spherical microgel particles in a single step, which allows us to freely incorporate functional materials into the polymer network. We used quantum dots, magnetic nanoparticles, and polymer microparticles as examples of the materials that can be added to provide specific chemical, physical, or mechanical properties to the original microgels. To generate the microgel particles, we constructed a capillary-based microfluidic device that generated pre-microgel drops, which were then polymerized in situ with a redox reaction. The capillary microfluidic device was made of three separate capillary tubes. The two internal cylindrical tubes served as injection and collection tubes and were coaxially aligned, as shown in the inset in Figure 1A. These tapered tubes were made by axially heating and pulling cylindrical capillaries. In the region near both tips, the outer fluid focuses both the middle and inner fluids through the collection tube to form a fluid thread that then breaks into drops as a result of hydrodynamic instabilities, as shown in Figure 1A. We typically used silicon oil with viscosity hOF= 125 mPas as the outer, or continuous-phase liquid. The middle fluid was an aqueous monomer solution that contained N-isopropylacrylamide (NIPAm, 15.5% w/v), a crosslinker (N,N’-methylenebisacrylamide, BIS, 1.5% w/v), a reaction accelerator (N,N,N’,N’-tetramethylethylenediamine, 2 vol%), and two co-monomers [2-(methacryloyloxy) ethyl trimethyl ammonium chloride (METAC, 2 vol%) and allylamine (1 vol%)]. METAC was added to increase the coil-toglobule transition temperature of poly(NIPAm), thereby facilitating homogeneous polymerization at room temperature. The allylamine adds amine groups to the network, which can subsequently be labeled with dyes after the formation of the microgel particles. The chemical formula [*] Dr. J. W. Kim, A. S. Utada, Dr. A. Fern ndez-Nieves, Prof. D. A. Weitz DEAS and Department of Physics Harvard University Cambridge, MA 02138 (USA) Fax: (+1)617-495-2875 E-mail: weitz@deas.harvard.edu

In vivo biomodification of lipid-coated carbon nanotubes by Daphnia magna.

Abstract: This study examined the interactions between Daphnia magna and a water-soluble, lysophophatidylcholine coated single-walled carbon nanotube. D. magna were able to ingest the nanotubes through normal feeding behavior and utilize the lysophophatidylcholine coating as a food source. D. magna were able to modify the solubility of the nanotube, likely through digestion of the lipid coating. This study provides evidence of biomodification of a carbon-based nanomaterial by an aquatic organism. The modification significantly altered the physical properties of the nanomaterial in freshwater. Acute toxicity was observed only in the highest test concentrations. These are important findings related to determining the behavior and potential toxicity of coated nanomaterials released into the environment.

Reduced Hippocampal Functional Connectivity in Alzheimer Disease

Abstract: Objective To determine if functional connectivity of the hippocampus is reduced in patients with Alzheimer disease. Design Functional connectivity magnetic resonance imaging was used to investigate coherence in the magnetic resonance signal between the hippocampus and all other regions of the brain. Participants Eight patients with probable Alzheimer disease and 8 healthy volunteers. Results Control subjects showed hippocampal functional connectivity with diffuse cortical, subcortical, and cerebellar sites, while patients demonstrated markedly reduced functional connectivity, including an absence of connectivity with the frontal lobes. Conclusion These findings suggest a functional disconnection between the hippocampus and other brain regions in patients with Alzheimer disease.

Fluorous metal-organic frameworks for high-density gas adsorption.

Abstract: A fluorous metal−organic framework, FMOF-1, is obtained by reaction of Ag(I) with 3,5-bis(trifluoromethyl)-1,2,4-triazolate, giving rise to a neutral, hydrogen-free, extended 3D nanotubular porous framework consisting of tetranuclear clusters [Ag4Tz6] connected by three-coordinate Ag(I) centers. The fluoro-lined channels and cavities of the framework show hysteretic adsorption of H2 with a volumetric capacity of 41 kg/m3 at 77 K and 64 bar. The framework also exhibits very high adsorptions for O2 and N2 with volumetric uptake of ∼550 and 400 kg/m3 at 77 K even at very low pressures (<10-2 bar).

The dynamic structure of management support systems: theory development, research focus, and direction

Abstract: Using a systems perspective, a conceptual model is developed that encompasses a broad class of systems whose fundamental purpose is the support of managerial actions and decision making. The term management support systems (MSS) is used to label this broad class. This model is based on an extensive review of the relevant literature and available research. The result provides an integrated systems model of the phenomena involved and points to gaps in the research that arise largely from the attempts to examine various classes of MSS as separate entities. The research presented here is based on the premise that there are fundamental core consistencies or similarities among various types of systems that have evolved in the past several decades to support decision making. It presents a conceptual, theoretical model drawn from findings about various types of support systems described in the literature such as decision support systems (DSS), executive information systems (EIS), knowledge management systems (KMS), and business intelligence (BI). Pragmatic insights are provided by the conceptual model and recommendations for future research are discussed.

The super-ordinate nature of the psychopathy checklist-revised.

Abstract: Psychopathy, while perhaps the earliest and most recognized personality disorder, is the subject of intense debate about its nature and measurement. The most recent proposal on its structural nature suggests that it is a multifaceted construct, made up of at least four dimensions reflecting Interpersonal, Affective, Lifestyle, and Antisocial anomalies (Hare & Neumann, 2005, 2006). These dimensions are significantly interrelated, suggesting that they are indicators for a super-ordinate factor. The nature of this higher-order factor may reflect the unifying feature which comprehensively defines the disorder. To examine this super-factor, the current study used several very large data sets of male (N = 4865) and female (N = 1099) offenders, and forensic psychiatric patients (N = 965), who were assessed with the Psychopathy ChecklistRevised (PCL-R; Hare, 2003). Structural equation modeling results indicated that the four first-order factor dimensions could be explained by a single second-order cohesive super-factor.

Transnational Rebels: Neighboring States as Sanctuary for Rebel Groups

Abstract: To what extent do international factors affect domestic conflict processes? How do external conditions affect the state's repressive capabilities and the opportunities for opposition groups to mobilize, launch an insurgency, and sustain it? This article argues that because state strength is limited by international boundaries, rebel groups often organize transnationally in order to evade repression. External bases, refugee communities, and characteristics of neighboring states are expected to increase the likelihood of civil war onset and continuation. Importantly, external mobilization is difficult for states to monitor and verify, a factor that exacerbates bargaining problems and increases the probability of armed conflict. These claims are tested through a quantitative analysis of civil conflicts from 1951 to 1999. Results suggest that weak neighbors, rival neighbors, and refugee diasporas contribute to rebellion and that conflicts endure longer when rebels have access to external bases.

Using Wikipedia for Automatic Word Sense Disambiguation

Abstract: This paper describes a method for generating sense-tagged data using Wikipedia as a source of sense annotations. Through word sense disambiguation experiments, the authors show that the Wikipedia-based sense annotations are reliable and can be used to construct accurate sense classifiers.

Unsupervised Graph-basedWord Sense Disambiguation Using Measures of Word Semantic Similarity

Abstract: This paper describes an unsupervised graph-based method for word sense disambiguation, and presents comparative evaluations using several measures of word semantic similarity and several algorithms for graph centrality. The results indicate that the right combination of similarity metrics and graph centrality algorithms can lead to a performance competing with the state-of-the-art in unsupervised word sense disambiguation, as measured on standard data sets.

Maximal oxygen uptake as a parametric measure of cardiorespiratory capacity

Abstract: Introduction:Maximal oxygen uptake (V˙O2max) was defined by Hill and Lupton in 1923 as the oxygen uptake attained during maximal exercise intensity that could not be increased despite further increases in exercise workload, thereby defining the limits of the cardiorespiratory system. This co

Collaborative Localization With Received-Signal Strength in Wireless Sensor Networks

Abstract: In this paper, we present an in-depth study of two collaborative-localization methods, called the multidimensional scaling (MDS) and maximum-likelihood estimator (MLE), for wireless sensor networks. From theoretical analysis, it is shown that MLE is more appropriate than MDS, given the underlying assumption of statistical signal models of the received-signal-strength-based localization problem. We also show that MDS can approximately achieve asymptotic efficiency with appropriate weighting schemes in some scenarios. From extensive simulation results, it is noted that the nonlinear least square algorithms that are commonly used to determine MLE are not as efficient as the iterative MDS algorithms. Thus, we propose a new integrated method MDS-MLE to effectively benefit from the strength of both methods. In the new method, MDS is used as an initialization method for MLE. With the solution of MDS as an initial value, MLE converges much faster and achieves significantly better performance than with random initial values. Superior performance of the new method is clearly demonstrated through simulation results. The effects of the deployment density of sensor nodes and reference nodes (RNs), as well as the deployment structure of RNs, are also studied through various simulations.

Strain-Rate Frequency Superposition: A Rheological Probe of Structural Relaxation in Soft Materials

Abstract: The rheological properties of soft materials often exhibit surprisingly universal linear and nonlinear features. Here we show that these properties can be unified by considering the effect of the strain-rate amplitude on the structural relaxation of the material. We present a new form of oscillatory rheology, strain-rate frequency superposition (SRFS), where the strain-rate amplitude is fixed as the frequency is varied. We show that SRFS can isolate the response due to structural relaxation, even when it occurs at frequencies too low to be accessible with standard techniques.

Photo-, thermally, and pH-responsive microgels.

Abstract: Microgels with photo-, thermally, and pH-responsive properties in aqueous suspension have been synthesized and characterized using dynamic light scattering and UV-visible spectroscopy. The new route involved first preparing poly(N-isopropylacrylamide) (PNIPAM)-allylamine copolymer microgels and a spiropyran photochrome (SP) bearing a carboxylic acid group. Then the functionalized spiropyran was coupled to the microgel via an amide bond. The dark-equilibrated gel particles feature spiropyran molecules in the polar, merocyanine form. After irradiation of visible light, the particle size becomes smaller because spiropyran changes to the relatively nonpolar, closed spiro form. The PNIPAM-SP microgels undergo a volume phase transition in water from a swollen state to a collapsed state with increasing temperature under all light conditions. However, the transition temperature range of the PNIPAM-SP is much broader than that for the PNIPAM without SP. The PNIPAM-SP microgels are monodisperse and self-assemble into a crystalline lattice while in suspension. The UV-visible spectra of an aqueous suspension of PNIPAM-SP microgel in the dark-adapted, merocyanine form showed both an absorption peak around 512 nm due to the merocyanine (giving a reddish color to the suspension) and two sharp peaks from Bragg diffraction of colloidal crystallites. Upon visible irradiation, the 512-nm band bleached significantly due to spiropyran photoisomerization. The spiropyran photoisomerization and accompanying color changes of the suspension were reversible upon alternating dark, UV, and visible light irradiation. Due to the residues of amine groups, the swelling capability of PNIPAM-SP microgels reduces as the pH value is changed from 7 to 10.

Sustaining the Peace: Determinants of Civil War Recurrence

Abstract: Over half of all civil wars that began and ended between 1944 and 1997 were followed by at least one if not more episodes of civil war We present a model to explain which characteristics of a civil war and the post-war environment make civil war more or less likely to recur We test this model with data on civil wars that began and ended between 1944 and 1997 Findings suggest that civil wars are less likely to recur following rebel victories and peace agreements supported by peacekeeping forces Post-war economic development also reduces the probability of civil war recurrence, and the longer the peace can be sustained, the less likely civil war is to recur These effects hold regardless of whether the previous war was ethnically based or not, and whether it was secessionist or revolutionary

Functional structure of cortical neuronal networks grown in vitro.

Abstract: We apply an information-theoretic treatment of action potential time series measured with microelectrode arrays to estimate the connectivity of mammalian neuronal cell assemblies grown in vitro. We infer connectivity between two neurons via the measurement of the mutual information between their spike trains. In addition we measure higher-point multi-information between any two spike trains, conditional on the activity of a third cell, as a means to identify and distinguish classes of functional connectivity among three neurons. The use of a conditional three-cell measure removes some interpretational shortcomings of the pairwise mutual information and sheds light on the functional connectivity arrangements of any three cells. We analyze the resultant connectivity graphs in light of other complex networks and demonstrate that, despite their ex vivo development, the connectivity maps derived from cultured neural assemblies are similar to other biological networks and display nontrivial structure in clustering coefficient, network diameter, and assortative mixing. Specifically we show that these networks are weakly disassortative small-world graphs, which differ significantly in their structure from randomized graphs with the same degree. We expect our analysis to be useful in identifying the computational motifs of a wide variety of complex networks, derived from time series data.

Cilia Proteins Control Cerebellar Morphogenesis by Promoting Expansion of the Granule Progenitor Pool

Abstract: Although human congenital cerebellar malformations are common, their molecular and developmental basis is still poorly understood. Recently, cilia-related gene deficiencies have been implicated in several congenital disorders that exhibit cerebellar abnormalities such as Joubert syndrome, Meckel-Gruber syndrome, Bardet-Biedl syndrome, and Orofaciodigital syndrome. The association of cilia gene mutations with these syndromes suggests that cilia may be important for cerebellar development, but the nature of cilia involvement has not been elucidated. To assess the importance of cilia-related proteins during cerebellar development, we studied the effects of CNS-specific inactivation of two mouse genes whose protein products are critical for cilia formation and maintenance, IFT88, (also known as polaris or Tg737), which encodes intraflagellar transport 88 homolog, and Kif3a, which encodes kinesin family member 3a. We showed that loss of either of these genes caused severe cerebellar hypoplasia and foliation abnormalities, primarily attributable to a failure of expansion of the neonatal granule cell progenitor population. In addition, granule cell progenitor proliferation was sensitive to partial loss of IFT function in a hypomorphic mutant of IFT88 (IFT88(orpk)), an effect that was modified by genetic background. IFT88 and Kif3a were not required for the specification and differentiation of most other cerebellar cell types, including Purkinje cells. Together, our observations constitute the first demonstration that cilia proteins are essential for normal cerebellar development and suggest that granule cell proliferation defects may be central to the cerebellar pathology in human cilia-related disorders.

Sheltering and Housing Recovery Following Disaster

Abstract: Reestablishing housing is a critical factor for understanding recovery processes, whether one is addressing the phenomenon at the household or community level. Researchers examining household or family recovery, for example, have utilized a variety of measures or indicators to capture different dimensions of recovery including psychological or perceptional measures related to stress, and sense of loss and recovery to more objective indicators such as regaining income, employment, household amenities, and household assets (Bates, 1982; Bolin, 1976, 1982, 1993, 1994; Bolin & Bolton, 1983; Bolin & Trainer, 1978; Peacock, Killian, & Bates, 1987). However, this research also suggests that fundamental to an overall assessment of household recovery is reestablishing permanent housing, or in the vernacular, home, because without establishing home, the ability of a household to carry out normal activities and reestablish a routine is limited and hampered (Bates & Peacock, 1987, 1993; Bolin & Trainer, 1978; Quarantelli, 1982). In short, delays in reestablishing housing all too often delay all other dimensions of recovery (Bolin, 1986).