A voxel-based formulation for contact finite element analysis

To date, voxel-based finite element models have not been feasible for contact problems, owing to the inherent stair-step boundary discontinuities. New preprocessing techniques are reported herein to mesh these boundaries smoothly, for purposes of contact stress analysis. Further, new techniques are reported to concentrate the mesh resolution automatically near the articular surface, thus reducing the problem size to levels compatible with executing nonlinear problems on contemporary engineering workstations. Close approximations to Hertzian analytical solutions were obtained for spherical and cylindrical geometries meshed in this manner, and an illustrative anatomical contact problem of the human hip joint is presented.     

Subject-specific geometry affects acetabular contact pressure during gait more than subject-specific loading patterns

Abstract

Finite element modeling (FEM) can predict hip cartilage contact mechanics. This study investigated how subject-specific boundary conditions and joint geometry affect acetabular cartilage contact mechanics using a multi-scale workflow. For two healthy subjects, musculoskeletal models calculated subject-specific hip kinematics and loading, which were used as boundary conditions for FEM. Cartilage contact mechanics were predicted using either generic or subject-specific FEM and boundary conditions. A subject-specific mesh resulted in a more lateral contact. Effects of subject-specific boundary conditions varied between both subjects. Results highlight the complex interplay between loading and kinematics and their effect on cartilage contact mechanics.     

Archaeological Evidence of the Cultural Importance of <Emphasis Type="Italic">Agave spp</Emphasis>. in Pre-Hispanic Colima,Mexico

Archaeological Evidence of the Cultural Importance of Agave spp . in Pre-Hispanic Colima, Mexico. Production of agave-based food and fermented alcoholic beverages was highly relevant culturally and socially in pre-European contact western Mesoamerica. It has been hypothesized that agave distillation in western Mexico began in Colima in the early Colonial Era through adaptation of introduced Filipino techniques. Archaeological evidence is presented confirming the cultural and social significance of agave in Colima before contact, one of the fundamental conditions supporting this hypothesis. An analysis of circular subterranean stone structures in residential and ceremonial contexts (Classic and Postclassic periods: 200–1500 common era [CE]), and a comparison with stone ovens currently used to cook agave for the creation of spirits, indicate these structures were probably used for preparing food, including agave. Analysis of funerary ceramic vessel offerings with agave images (Colima phase: 400–600 CE) are reported for the first time. Their characteristics, and those of the associated burials and tombs, suggest those buried were agave growers or alcoholic beverage producers who fulfilled relevant roles in the society. Most of the agave images probably represent Agave angustifolia Lem and its cultivation. During the Colonial Era, the cultural and social relevance of agaves almost disappeared in Colima, possibly due to drastic reductions in the native human population, changing land use practices, and prohibitions against the production and sale of native alcoholic beverages.     

Assessment of the Effect of Mesh Density on the Material Property Discretisation Within QCT Based FE Models: A Practical Example Using the Implanted Proximal Tibia

A three-dimensional, quantitative computed tomography based finite element model of a proximal implanted tibia was analysed in order to assess the effect of mesh density on material property discretisation and the resulting influence on the predicted stress distribution. The mesh was refined on the contact surfaces (matched meshes) with element sizes of 3, 2, 1.4, 1 and 0.8 mm. The same loading conditions were used in all models (bi-condylar load: 60% medial, 40% lateral). Significant variations were observed in the modulus distributions between the coarsest and finest mesh densities. Poor discretisation of the material properties also resulted in poor correlations of the stresses and risk ratios between the coarsest and finest meshes. Little difference in Young's modulus, von Mises stress and risk ratio distributions were observed between the three finest models; hence, it was concluded that for this particular case an element size of 1.4 mm on the contact surfaces was enough to properly describe the stiffness, stress and risk ratio distributions within the bone. Poor convergence of the material property distribution occurred when the element size was significantly larger than the pixel size of the source CT data. It was concluded that unless there is convergence in the Young's modulus distribution, convergence of the stress field or of other parameters of interest will not occur either.     

Barriers to Social Participation among Lonely Older Adults: The Influence of Social Fears and Identity

IntroductionLoneliness among older adults is a major public health problem that may be associated with processes of social participation and identity. This study therefore sought to examine the relationship between social participation and identity in a sample of lonely older adults living independently in London, England.MethodAn inductive qualitative approach, based on semi-structured interviews and thematic analysis, was employed.ResultsParticipants commonly spoke of barriers to social participation that have been reported elsewhere, including illness/disability, loss of contact with friends/relatives, lack of a supportive community, and lack of acceptable social opportunities. However, novel findings were also derived. In particular, participants commonly minimised the difficulties they faced alone, and described attempts to avoid social opportunities. These behaviours were linked to fears about engaging in social participation opportunities, including fears of social rejection and/or exploitation, and fears of losing valued aspects of identity.DiscussionIt is concluded that social participation amongst lonely older people will not improve through the removal of previously reported barriers alone; instead, older peoples’ beliefs, fears and identities must be addressed. Suggestions for implementing these findings within community organisations are provided.     

Computer Simulation of Aqueous Biomolecular Systems

Abstract

Computer simulation techniques are increasingly being used to predict structural and thermodynamic properties of large heterogeneous macromolecule and solvent assemblies. We discuss, with examples from our own studies, some problems we and others have experienced in using these techniques, which were originally devised for simple liquids. In particular, we consider the problems which arise from the large size and heterogeneity of macromolecule water systems, comparisons with experimental data and equilibration and sampling procedures.     

Deepening our understanding of HDL proteome

ABSTRACT

Introduction: High-density lipoprotein (HDL) particles are heterogeneous and their proteome is complex and distinct from HDL cholesterol. However, it is largely unknown whether HDL proteins are associated with cardiovascular protection.

Areas covered: HDL isolation techniques and proteomic analyses are reviewed. A list of HDL proteins reported in 37 different studies was compiled and the effects of different isolation techniques on proteins attributed to HDL are discussed. Mass spectrometric techniques used for HDL analysis and the need for precise and robust methods for quantification of HDL proteins are discussed.

Expert opinion: Proteins associated with HDL have the potential to be used as biomarkers and/or help to understand HDL functionality. To achieve this, large cohorts must be studied using precise quantification methods. Key factors in HDL proteome quantification are the isolation methodology and the mass spectrometry technique employed. Isolation methodology affects what proteins are identified in HDL and the specificity of association with HDL particles needs to be addressed. Shotgun proteomics yields imprecise quantification, but the majority of HDL studies relied on this approach. Few recent studies used targeted tandem mass spectrometry to quantify HDL proteins, and it is imperative that future studies focus on the application of these precise techniques.     

Receptor Autoradiography: The Last Ten Years

Abstract

The development of techniques for the microscopic visualization of receptor binding and other binding sites using autoradiography is reviewed. The application of these techniques to a number of pharmacological problems, particularly in the field of neuropharmacology is illustrated. The limitations and future trends in the field of receptor visualization are commented upon.     

Positive Contrast MRI Techniques for Visualization of Iron-Loaded Hernia Mesh Implants in Patients

ObjectIn MRI, implants and devices can be delineated via susceptibility artefacts. To discriminate susceptibility voids from proton-free structures, different positive contrast techniques were implemented. The purpose of this study was to evaluate a pulse sequence-based positive contrast technique (PCSI) and a post-processing susceptibility gradient mapping algorithm (SGM) for visualization of iron loaded mesh implants in patients.ResultsOn GRE, the iron-loaded meshes generated distinct susceptibility-induced signal voids. PCSI exhibited susceptibility differences including the meshes as hyperintense signals. SGM exhibited susceptibility differences with positive contrast. Visually, the different algorithms presented no significant differences. Overall, the diagnostic value was rated best in GRE whereas PCSI and SGM were barely “sufficient”.ConclusionBoth “positive contrast” techniques depicted implanted meshes with hyperintense signal. SGM comes without additional acquisition time and can therefore be utilized in every patient.     

Terpenoids constituents of Euphorbia sapinii

The investigation of an acetone extract of whole Euphorbia sapinii led to the isolation of eighteen terpenoids among which lanost-24-en-20-ol-3-tetradecanoate (1), euphorbol-7-one (2) are new while spectroscopic data of 30-nor-hopan-3β-ol-22-one (3) are reported for the first time. The structures of all compounds were determined using 1D, 2D NMR and MS techniques.     

Changes in Parkinsonian gait kinematics with self-generated and externally-generated cues: a comparison of responders and non-responders

Abstract

Purpose: Rhythmic auditory stimulation such as listening to music can alleviate gait bradykinesia in people with Parkinson disease (PD) by increasing spatiotemporal gait features. However, evidence about what specific kinematic alterations lead to these improvements is limited, and differences in responsiveness to cueing likely affect individual motor strategies. Self-generated cueing techniques, such as singing or mental singing, provide similar benefits but no evidence exists about how these techniques affect lower limb joint movement. In this study, we assessed immediate effects of external and self-generated cueing on lower limb movement trajectories during gait.

Methods: Using 3D motion capture, we assessed sagittal plane joint angles at the hip, knee, and ankle across 35 participants with PD, divided into responders (n?=?23) and non-responders (n?=?12) based on a clinically meaningful change in gait speed. Joint motion was assessed as overall range of motion as well as at two key time points during the gait cycle: initial contact and toe-off.

Results: Responders used both cue types to increase gait speed and induce increases in overall joint ROM at the hip while only self-generated cues also increased ROM at the ankle. Increased joint excursions for responders were also evident at initial contact and toe-off.

Conclusions: Our results indicate that self-generated rhythmic cues can induce similar increases in joint excursions as externally-generated cues and that some people may respond more positively than others. These results provide important insight into how self-generated cueing techniques may be tailored to meet the varied individual needs of people with PD.     

Acridine orange interaction with DNA: Effect of ionic strength

BackgroundThe study of acridine orange (AO) spectral characteristics and the quenching of its singlet and triplet excited states by TEMPO radical at its binding to DNA in the function of the DNA concentration and in the absence and presence of NaCl is reported.MethodsThe study was performed using steady-state and time resolved optical absorption and florescence, fluorescence correlation spectroscopy and resonant light scattering techniques.ResultsThe presence of different species in equilibrium: AO monomers and aggregates bound to DNA, has been demonstrated, their relative content depending on the DNA and the AO concentrations. At high DNA concentration the AO monomers are protected against the contact with other molecules, thus reducing the AO excited state quenching. The addition of NaCl reduces the AO binding constant to DNA, thus reducing the AO and DNA aggregation.ConclusionsThe interaction of AO with DNA is a complex process, including aggregation and disaggregation of both components. This modifies the AO excited state characteristics and AO accessibility to other molecules. The salt reduces the DNA effects on the AO excited state characteristics thus attenuating its effects on the AO efficacy in applications.General significanceThis study demonstrates that the interaction of photosensitizers with DNA, depending on their relative concentrations, can both decrease and increase the photosensitizer efficacy in applications. The salt is able to attenuate these effects.     

Leprosy New Case Detection Trends and the Future Effect of Preventive Interventions in Pará State,Brazil: A Modelling Study

BackgroundLeprosy remains a public health problem in Brazil. Although the overall number of new cases is declining, there are still areas with a high disease burden, such as Pará State in the north of the country. We aim to predict future trends in new case detection rate (NCDR) and explore the potential impact of contact tracing and chemoprophylaxis on NCDR in Pará State.MethodsWe used SIMCOLEP, an existing individual-based model for the transmission and control of M. leprae, in a population structured by households. The model was quantified to simulate the population and observed NCDR of leprosy in Pará State for the period 1990 to 2014. The baseline scenario was the current control program, consisting of multidrug therapy, passive case detection, and active case detection from 2003 onwards. Future projections of the NCDR were made until 2050 given the continuation of the current control program (i.e. baseline). We further investigated the potential impact of two scenarios for future control of leprosy: 1) discontinuation of contact tracing; and 2) continuation of current control in combination with chemoprophylaxis. Both scenarios started in 2015 and were projected until 2050.ResultsThe modelled NCDR in Pará State after 2014 shows a continuous downward trend, reaching the official elimination target of 10 cases per 100,000 population by 2030. The cessation of systematic contact tracing would not result in a higher NCDR in the long run. Systematic contact tracing in combination with chemoprophylaxis for contacts would reduce the NCDR by 40% and bring attainment of the elimination target two years forward to 2028.ConclusionThe NCDR of leprosy continues to decrease in Pará State. Elimination of leprosy as a public health problem could possibly be achieved around 2030, if the current control program is maintained. Providing chemoprophylaxis would decrease the NCDR further and would bring elimination forward by two years.     

Assessment of ablation catheter contact on valve annulus: Implications on accessory pathway ablation

BackgroundCatheter-tissue contact force is an important factor influencing lesion size and efficacy and thereby potential for arrhythmia recurrence following accessory pathway (AP) radiofrequency ablation. We aim to evaluate adequacy and perception of catheter contact on the tricuspid and mitral annuli.MethodsData were collected from 42 patients undergoing catheter ablation. Operators were blinded to contact force information and reported perceived contact (poor, moderate, or good) while positioning the catheter at four tricuspid annular sites (12, 9, 6 and 4 o'clock positions; abbreviated as TA12, TA9, TA6 and TA4) and three mitral annular sites (3, 5 and 7 o'clock positions; abbreviated as MA3, MA5 and MA7) through long vascular sheaths.ResultsThe highest and lowest mean contact forces were obtained at MA7 (13.3 ± 1.7 g) and TA12 (3.6 g ± 1.3 g) respectively. Mean contact force on tricuspid annulus (6.1 g ± 0.9 g) was lower than mitral annulus (9.8 ± 0.9 g) locations (p = 0.0036), with greater proportion of sites with <10 g contact force (81.7% vs 60.4%; p = 0.0075). Perceived contact had no impact on measured mean contact force for both mitral and tricuspid annular positions (p = 0.959 and 0.671 respectively). There was correlation of both impedance and atrial electrogram amplitude with contact force, though insufficient to be clinically applicable.ConclusionA high proportion of annular catheter applications have low contact force despite being performed with long vascular sheaths in the hands of experienced operators. In addition, there was no impact of operator perceived contact force on actual measured contact force. This may carry implications for success of AP ablation.     

Baggasse Preservation: A Need for a Biotechnological Approach

ABSTRACT

Microarrays with biomolecules (e.g., DNA and proteins), cells, and tissues immobilized on solid substrates are important tools for biological research, including genomics, proteomics, and cell analysis. In this paper, the current state of microarray fabrication is reviewed. According to spot formation techniques, methods are categorized as “contact printing” and “non-contact printing.” Contact printing is a widely used technology, comprising methods such as contact pin printing and microstamping. These methods have many advantages, including reproducibility of printed spots and facile maintenance, as well as drawbacks, including low-throughput fabrication of arrays. Non-contact printing techniques are newer and more varied, comprising photochemistry-based methods, laser writing, electrospray deposition, and inkjet technologies. These technologies emerged from other applications and have the potential to increase microarray fabrication throughput; however, there are several challenges in applying them to microarray fabrication, including interference from satellite drops and biomolecule denaturization.     

Systematic review of comparative efficacy and tolerability of calcipotriol in treating chronic plaque psoriasis

ObjectivesTo evaluate the comparative efficacy and tolerability of topical calcipotriol in the treatment of mild to moderate chronic plaque psoriasis.DesignQuantitative systematic review of randomised controlled trials.Subjects6038 patients with plaque psoriasis reported in 37 trials.ResultsCalcipotriol was at least as effective as potent topical corticosteroids, calcitriol, short contact dithranol, tacalcitol, coal tar, and combined coal tar 5%, allantoin 2%, and hydrocortisone 0.5%. Calcipotriol caused significantly more skin irritation than potent topical corticosteroids (number needed to treat to harm for irritation 10, 95% confidence interval 6 to 34). Calcipotriol monotherapy also caused more irritation than calcipotriol combined with a potent topical corticosteroid (6, 4 to 8). However, the number needed to treat for dithranol to produce lesional or perilesional irritation was 4 (3 to 5). On average, treating 23 patients with short contact dithranol led to one more patient dropping out of treatment owing to adverse effects than if they were treated with calcipotriol.ConclusionsCalcipotriol is an effective treatment for mild to moderate chronic plaque psoriasis, more so than calcitriol, tacalcitol, coal tar, and short contact dithranol. Only potent topical corticosteroids seem to have comparable efficacy at eight weeks. Although calcipotriol caused more skin irritation than topical corticosteroids this has to be balanced against the potential long term effects of corticosteroids. Skin irritation rarely led to withdrawal of calcipotriol treatment. Longer term comparative trials of calcipotriol versus dithranol and topical corticosteroids are needed to see whether these short term benefits are mirrored by long term outcomes such as duration of remission and improvement in quality of life.     

Genetic counseling and the presenile dementias

Abstract

The clinical application of genetic counseling techniques to the presenile dementing illnesses is discussed, using examples. The problems encountered in adult‐onset illness are very different from those seen in illnesses affecting children. Some general guidelines and some specific ones are presented.     

Infestation by the mite Harpirhynchus nidulans in the Bearded Tit Panurus biarmicus

Capsule Mites sometimes induced voluminous subcutaneous cysts in featherless parts.

Aims To describe the first reported infestation by the skin-dweller mite Harpirhynchus nidulans in Bearded Tits Panurus biarmicus and for the Timaliidae family, to detect possible fitness costs for the host and to determine the distribution of the parasite within the distribution range of the host.

Methods Parasites were identified using a microscope. Wing-length and body mass were recorded on both uninfected and infected birds captured at different times during the year. We also considered historical data, and contact was made with 32 European ringing stations to identify the distribution range of the parasite.

Results Subcutaneous reproduction of the mite Harpirhynchus nidulans induced the development of voluminous dermal nodules in Panurus biarmicus. There were no differences in body mass or wing-length with respect to infestation. In the south of France, prevalence changed from 10.6% in spring to 4.7% in autumn. Both sexes are equally parasitized. Occurrence of dermal cysts is reported from several southern European populations of Bearded Tits, whereas it seems to be absent from northern latitudes.

Conclusion The occurrence of a Harpirhynchus mite in wild bird populations is reported for the first time. We consider aspects of its biology, host–parasite system, host-specificity, co-adaptation of the mite reproductive cycle to the social dynamics of its host and metapopulational host–parasite dynamics.     

Genomic duplication problems for unrooted gene trees

Background

Discovering the location of gene duplications and multiple gene duplication episodes is a fundamental issue in evolutionary molecular biology. The problem introduced by Guigó et al. in 1996 is to map gene duplication events from a collection of rooted, binary gene family trees onto theirs corresponding rooted binary species tree in such a way that the total number of multiple gene duplication episodes is minimized. There are several models in the literature that specify how gene duplications from gene families can be interpreted as one duplication episode. However, in all duplication episode problems gene trees are rooted. This restriction limits the applicability, since unrooted gene family trees are frequently inferred by phylogenetic methods.

Results

In this article we show the first solution to the open problem of episode clustering where the input gene family trees are unrooted. In particular, by using theoretical properties of unrooted reconciliation, we show an efficient algorithm that reduces this problem into the episode clustering problems defined for rooted trees. We show theoretical properties of the reduction algorithm and evaluation of empirical datasets.

Conclusions

We provided algorithms and tools that were successfully applied to several empirical datasets. In particular, our comparative study shows that we can improve known results on genomic duplication inference from real datasets.