Effects of Drag-Reducing Polymers on Hemodynamics and Whole Blood-Endothelial Interactions in 3D-Printed Vascular Topologies

Most in vitro models use culture medium to apply fluid shear stress to endothelial cells, which does not capture the interaction between blood and endothelial cells. Here, we describe a new system to characterize whole blood flow through a 3D-printed, endothelialized vascular topology that induces flow separation at a bifurcation. Drag-reducing polymers, which have been previously studied as a potential therapy to reduce the pressure drop across the vascular bed, are evaluated for their effect on mitigating the disturbed flow. Polymer concentrations of 1000 ppm prevented recirculation and disturbed flow at the wall. Proteomic analysis of plasma collected from whole blood recirculated through the vascularized channel with and without drag-reducing polymers provides insight into the effects of flow regimes on levels of proteins indicative of the endothelial-blood interaction. The results indicate that blood flow alters proteins associated with coagulation, inflammation, and other processes. Overall, these proof-of-concept experiments demonstrate the importance of using whole blood flow to study the endothelial response to perfusion.

Development and internal validation of a diagnostic prediction model for COVID-19 at time of admission to hospital

BACKGROUND

Early coronavirus disease 2019 (COVID-19) diagnosis prior to laboratory testing results is crucial for infection control in hospitals. Models exist predicting COVID-19 diagnosis, but significant concerns exist regarding methodology and generalizability.

AIM

To generate the first COVID-19 diagnosis risk score for use at the time of hospital admission using the TRIPOD (transparent reporting of a multivariable prediction model for individual prognosis or diagnosis) checklist.

DESIGN

A multivariable diagnostic prediction model for COVID-19 using the TRIPOD checklist applied to a large single-centre retrospective observational study of patients with suspected COVID-19.

METHODS

581 individuals were admitted with suspected COVID-19; the majority had laboratory-confirmed COVID-19 (420/581, 72.2%). Retrospective collection was performed of electronic clinical records and pathology data.

RESULTS

The final multivariable model demonstrated AUC 0.8535 (95% confidence interval 0.8121-0.8950). The final model used six clinical variables that are routinely available in most low and high-resource settings. Using a cut-off of 2, the derived risk score has a sensitivity of 78.1% and specificity of 86.8%. At COVID-19 prevalence of 10% the model has a negative predictive value (NPV) of 96.5%.

CONCLUSIONS

Our risk score is intended for diagnosis of COVID-19 in individuals admitted to hospital with suspected COVID-19. The score is the first developed for COVID-19 diagnosis using the TRIPOD checklist. It may be effective as a tool to rule out COVID-19 and function at different pandemic phases of variable COVID-19 prevalence. The simple score could be used by any healthcare worker to support hospital infection control prior to laboratory testing results.

Constitutive Model of Radiation Aging Effects in Filled Silicone Elastomers under Strain

Filled silicone elastomers, an essential component in many technological applications, are often subjected to controlled or unintended radiation for a variety of reasons. Radiation exposure can lead to permanent mechanical and structural changes in the material, which is manifested as altered mechanical response, and in some cases, a permanent set. For unfilled elastomers, network theories developed and refined over decades can explain these effects in terms of chain-scission and cross-link formation and a hypothesis involving independent networks formed at different strain levels of the material. Here, we expose a filled silicone rubber to gamma radiation while being under finite elongational strain and show that the observed mechanical and structural changes can be quantitatively modeled within the same theoretical framework developed for unfilled elastomers as long as nuances associated with the Mullins effect are accounted for in a consistent manner. In this work, we employ Ogden's incompressible hyperelastic model within the framework of Tobolsky's two-network scheme to describe the observed permanent set and mechanical modulus changes as a function of radiation dosage. In the process, we conclude that gamma radiation induces both direct cross-linking at chain crossings (H-links) and main-chain-scission followed by cross-linking (Y-links). We provide an estimate of the ratio of chain-scission to cross-linking rates, which is in reasonable agreement with previous experimental estimate from Charlesby-Pinner analysis. We use density functional theory (DFT)-based quantum mechanical calculations to explore the stability of -Si and -SiO radicals that form upon a radiation-induced chain-scission event, which sheds light on the relative rates of Y-linking and H-linking processes.

Non-Abelian Bloch oscillations in higher-order topological insulators

Bloch oscillations (BOs) are a fundamental phenomenon by which a wave packet undergoes a periodic motion in a lattice when subjected to a force. Observed in a wide range of synthetic systems, BOs are intrinsically related to geometric and topological properties of the underlying band structure. This has established BOs as a prominent tool for the detection of Berry-phase effects, including those described by non-Abelian gauge fields. In this work, we unveil a unique topological effect that manifests in the BOs of higher-order topological insulators through the interplay of non-Abelian Berry curvature and quantized Wilson loops. It is characterized by an oscillating Hall drift synchronized with a topologically-protected inter-band beating and a multiplied Bloch period. We elucidate that the origin of this synchronization mechanism relies on the periodic quantum dynamics of Wannier centers. Our work paves the way to the experimental detection of non-Abelian topological properties through the measurement of Berry phases and center-of-mass displacements.

Detecting Fractional Chern Insulators through Circular Dichroism

Great efforts are currently devoted to the engineering of topological Bloch bands in ultracold atomic gases. Recent achievements in this direction, together with the possibility of tuning interparticle interactions, suggest that strongly correlated states reminiscent of fractional quantum Hall (FQH) liquids could soon be generated in these systems. In this experimental framework, where transport measurements are limited, identifying unambiguous signatures of FQH-type states constitutes a challenge on its own. Here, we demonstrate that the fractional nature of the quantized Hall conductance, a fundamental characteristic of FQH states, could be detected in ultracold gases through a circular-dichroic measurement, namely, by monitoring the energy absorbed by the atomic cloud upon a circular drive. We validate this approach by comparing the circular-dichroic signal to the many-body Chern number and discuss how such measurements could be performed to distinguish FQH-type states from competing states. Our scheme offers a practical tool for the detection of topologically ordered states in quantum-engineered systems, with potential applications in solid state.

Parametric heating in a 2D periodically-driven bosonic system: Beyond the weakly-interacting regime

We experimentally investigate the effects of parametric instabilities on the short-time heating process of periodically-driven bosons in 2D optical lattices with a continuous transverse (tube) degree of freedom. We analyze three types of periodic drives: (i) linear along the x-lattice direction only, (ii) linear along the lattice diagonal, and (iii) circular in the lattice plane. In all cases, we demonstrate that the BEC decay is dominated by the emergence of unstable Bogoliubov modes, rather than scattering in higher Floquet bands, in agreement with recent theoretical predictions. The observed BEC depletion rates are much higher when shaking both along x and y directions, as opposed to only x or only y. We also report an explosion of the decay rates at large drive amplitudes, and suggest a phenomenological description beyond Bogoliubov theory. In this strongly-coupled regime, circular drives heat faster than diagonal drives, which illustrates the non-trivial dependence of the heating on the choice of drive.

Four-Dimensional Quantum Hall Effect with Ultracold Atoms

We propose a realistic scheme to detect the 4D quantum Hall effect using ultracold atoms. Based on contemporary technology, motion along a synthetic fourth dimension can be accomplished through controlled transitions between internal states of atoms arranged in a 3D optical lattice. From a semiclassical analysis, we identify the linear and nonlinear quantized current responses of our 4D model, relating these to the topology of the Bloch bands. We then propose experimental protocols, based on current or center-of-mass-drift measurements, to extract the topological second Chern number. Our proposal sets the stage for the exploration of novel topological phases in higher dimensions.

Light-induced gauge fields for ultracold atoms

Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle-the graviton-that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms 'feeling' laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials-both Abelian and non-Abelian-in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms.

Synthetic gauge fields in synthetic dimensions

We describe a simple technique for generating a cold-atom lattice pierced by a uniform magnetic field. Our method is to extend a one-dimensional optical lattice into the "dimension" provided by the internal atomic degrees of freedom, yielding a synthetic two-dimensional lattice. Suitable laser coupling between these internal states leads to a uniform magnetic flux within the two-dimensional lattice. We show that this setup reproduces the main features of magnetic lattice systems, such as the fractal Hofstadter-butterfly spectrum and the chiral edge states of the associated Chern insulating phases.

Comparative effectiveness of robotic versus laparoscopic hysterectomy for endometrial cancer

PURPOSE

Use of robotics in oncologic surgery is increasing; however, reports of safety and efficacy are from highly experienced surgeons and centers. We performed a population-based analysis to compare laparoscopic hysterectomy and robotic hysterectomy for endometrial cancer.

PATIENTS AND METHODS

The Perspective database was used to identify women who underwent a minimally invasive hysterectomy for endometrial cancer from 2008 to 2010. Morbidity, mortality, and cost were evaluated using multivariable logistic and linear regression models.

RESULTS

We identified 2,464 women, including 1,027 (41.7%) who underwent laparoscopic hysterectomy and 1,437 (58.3%) who underwent robotic hysterectomy. Women treated at larger hospitals, nonteaching hospitals, and centers outside of the northeast were more likely to undergo a robotic hysterectomy procedure, whereas black women, those without insurance, and women in rural areas were less likely to undergo a robotic hysterectomy procedure (P < .05 for all). The overall complication rate was 9.8% for laparoscopic hysterectomy versus 8.1% for robotic hysterectomy (P = .13). The adjusted odds ratio (OR) for any morbidity for robotic hysterectomy was 0.76 (95% CI, 0.56 to 1.03). After adjusting for patient, surgeon, and hospital characteristics, there were no significant differences in the rates of intraoperative complications (OR, 0.68; 95% CI, 0.42 to 1.08), surgical site complications (OR, 1.49; 95% CI, 0.81 to 2.73), medical complications (OR, 0.64; 95% CI, 0.40 to 1.01), or prolonged hospitalization (OR, 0.85; 95% CI, 0.64 to 1.14) between the procedures. The mean cost for robotic hysterectomy was $10,618 versus $8,996 for laparoscopic hysterectomy (P < .001). In a multivariable model, robotic hysterectomy was significantly more costly ($1,291; 95% CI, $985 to $1,597).

CONCLUSION

Despite claims of decreased complications with robotic hysterectomy, we found similar morbidity but increased cost compared with laparoscopic hysterectomy. Comparative long-term efficacy data are needed to justify its widespread use.

Realistic time-reversal invariant topological insulators with neutral atoms

We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. We introduce an original method to synthesize a gauge field in the near field of an atom chip, which effectively mimics the effects of spin-orbit coupling and produces quantum spin-Hall states. We also propose a feasible scheme to engineer sharp boundaries where the hallmark edge states are localized. Our multiband system has a large parameter space exhibiting a variety of quantum phase transitions between topological and normal insulating phases. Because of their remarkable versatility, cold-atom systems are ideally suited to realize topological states of matter and drive the development of topological quantum computing.

Wilson fermions and axion electrodynamics in optical lattices

We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3+1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.

Erlotinib added to carboplatin and paclitaxel as first-line treatment of ovarian cancer: a phase II study based on surgical reassessment

BACKGROUND

The purpose of this study was to determine whether adding the anti-epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib to carboplatin/paclitaxel improved pathologic complete response (pCR) at reassessment surgery in epithelial ovarian, fallopian tube, or primary peritoneal cancers (OFPC).

METHODS

Patients with stage III-IV OFPC initiated treatment within 12 weeks of initial cytoreductive surgery or, after histologic confirmation of diagnosis, neoadjuvantly. Treatment included paclitaxel (175 mg/m²) and carboplatin (AUC 6) every 3 weeks for up to 6 cycles, plus oral erlotinib 150 mg daily. The primary objective was to determine whether the pCR rate at reassessment surgery was at least 60% after optimal cytoreduction at initial surgery (< 1cm residual disease), or at least 40% after suboptimal cytoreduction (at least 1cm residual disease) using a two-stage design (alpha=0.10, beta=0.10).

RESULTS

The study population included 56 patients with stage III-IV OFPC. EGFR gene amplification was present in 15% of the 20 tumors evaluated. Twenty-eight patients had protocol therapy after optimal cytoreduction (stratum I), 23 had protocol therapy either after suboptimal cytoreduction (stratum II), and 5 received neoadjuvant therapy prior to cytoreduction (stratum III). Pathologic CR was confirmed in 8 patients (29%; 95% confidence intervals 13%, 49%) in stratum I and 3 patients (11%, 95% C.I. 2%, 28%) in stratum II, which did not meet the prespecified efficacy endpoint in either stratum.

CONCLUSIONS

Among unselected patients, erlotinib plus carboplatin-paclitaxel did not improve pCR rates compared with historical experience with carboplatin-paclitaxel alone in patients with stage III-IV OFPC.

Does social status predict adult smoking and obesity? Results from the 2000 Mexican National Health Survey

Socioeconomic status is generally associated with better health, but recent evidence suggests that this 'social gradient' in health is far from universal. This study examines whether social gradients in smoking and obesity in Mexico - a country in the midst of rapid socioeconomic change - conform to or diverge from results for richer countries. Using a nationally representative sample of 39,129 Mexican adults, we calculate the odds of smoking and of being obese by educational attainment and by household wealth. We conclude that socioeconomic determinants of smoking and obesity in Mexico are complex, with some flat gradients and some strong positive or negative gradients. Higher social status (education and assets) is associated with more smoking and less obesity for urban women. Higher status rural women also smoke more, but obesity for these women has a non-linear relationship to education. For urban men, higher asset levels (but not education) are associated with obesity, whereas education is protective of smoking. Higher status rural men with more assets are more likely to smoke and be obese. As household wealth, education and urbanisation continue to increase in Mexico, these patterns suggest potential targets for public health intervention now and in the future.

Paclitaxel plus oxaliplatin for recurrent or metastatic cervical cancer: a New York Cancer Consortium Study

OBJECTIVE

Survival in women with recurrent or metastatic cervical cancer remains poor. More effective and less toxic regimens are needed. Cisplatin is an effective radiosensitizer, but its single agent activity in recurrent cervical cancer, especially after prior cisplatin exposure, is disappointing, with a response rate of only 13%. Oxaliplatin has preclinical activity in cisplatin-resistant tumors and may have synergic activity when combined with paclitaxel. Our objective is to determine the efficacy and toxicity of paclitaxel and oxaliplatin in patients with recurrent or metastatic cervical cancer.

METHODS

Patients with histologic confirmation of primary metastatic or recurrent cervical cancer not amenable to surgical management were eligible. Treatment consisted of paclitaxel 175 mg/m(2) IV and oxaliplatin 130 mg/m(2) IV every 21 days. The primary endpoints were toxicity, recorded every cycle, and response, determined by RECIST criteria and were assessed every 9 weeks, with subsequent confirmation as required. Sample size determinations were made using a Simon's two-stage design with a projected overall response proportion of 13% with cisplatin alone. Survival rates were calculated with Kaplan-Meier methods.

RESULTS

Of the 35 patients enrolled, 32 were evaluable. The median age was 56 (27-78); 30 had had prior radiation (23 concomitant with cisplatin). Patients completed a mean of 4.2 cycles (1-11). There were 2 complete and 5 partial responses for a total response rate of 7/32 (22%; 95% CI: 9.3%-40.0%). Eight patients had stable disease for an overall clinical benefit rate of 15/32 (47%; 95% CI: 29.1%-65.3%). The mean time to best response was 13.5 weeks (95% CI: 10.6, 16.4). The mean progression-free survival was 21 weeks (95% CI: 14.7, 27.2) and mean overall survival was 52 weeks (95% CI: 39.4, 64.8). A total of 135 cycles were administered. There were 28 (20.1%) grade 3/4 hematologic toxicities and 46 (34.1%) grade 3/4 non-hematologic toxicities, which were predominantly sensory neuropathy. There were 13 treatment delays, 4 dose reductions, and no treatment-related deaths.

CONCLUSIONS

The combination of paclitaxel and oxaliplatin is an effective regimen in patients with recurrent or persistent cervical cancer including a majority previously exposed to cisplatin. Further study and comparison with other platinum-based regimens is warranted.

Fertility preservation in young women with epithelial ovarian cancer

BACKGROUND

Surgical management of ovarian cancer consists of hysterectomy with bilateral oophorectomy. In young women, this results in the loss of reproductive function and estrogen deprivation. In the current study, the authors examined the safety of fertility-conserving surgery in premenopausal women with epithelial ovarian cancers.

METHODS

Women aged<or=50 years with stage IA or IC epithelial ovarian cancer who were registered in the Surveillance, Epidemiology, and End Results database were examined. Patients who underwent bilateral oophorectomy were compared with those who underwent ovarian conservation. A second analysis examined uterine conservation versus hysterectomy. Multivariate Poisson regression models were developed to describe predictors of fertility preservation. Survival was examined using Cox proportional hazards models and the Kaplan-Meier method.

RESULTS

In total, 1186 women, including 754 women (64%) who underwent bilateral oophorectomy and 432 women (36%) who underwent ovarian preservation, were identified. Younger age, later year of diagnosis, and residence in the eastern or western United States were associated with ovarian preservation (P<.05 for all). Women with endometrioid and clear cell histologies and stage IC disease were less likely to have ovarian conservation (P<.05). In a Cox model, ovarian preservation had no effect on survival (hazard ratio [HR], 0.69; 95% confidence interval [CI], 0.39-1.20). Young age, later year of diagnosis, residence in the eastern or western United States, single women, mucinous tumors, and patients with stage IA disease were more likely to have uterine preservation (P<.05 for all). In a multivariate model, uterine preservation had no effect on survival (HR, 0.87; 95% CI, 0.62-1.22).

CONCLUSIONS

Ovarian and uterine-conserving surgery were safe in young women who had stage IA and IC epithelial ovarian cancer.

Non-Abelian optical lattices: anomalous quantum Hall effect and Dirac fermions

We study the properties of an ultracold Fermi gas loaded in an optical square lattice and subjected to an external and classical non-Abelian gauge field. We show that this system can be exploited as an optical analogue of relativistic quantum electrodynamics, offering a remarkable route to access the exotic properties of massless Dirac fermions with cold atoms experiments. In particular, we show that the underlying Minkowski space-time can also be modified, reaching anisotropic regimes where a remarkable anomalous quantum Hall effect and a squeezed Landau vacuum could be observed.

An Incremental Step in Patient Safety: Reducing the Risks of Retained Foreign Bodies by the Use of an Integrated Laparotomy Pad/Retractor

Retained foreign body is a recognized complication of abdominal, pelvic, and thoracic surgery and a cause of medical malpractice. Efforts to reduce its incidence include safe exposure and the use of fewer laparotomy pads. The EZ DASH is an absorbent 12-thickness laparotomy pad covering a malleable stainless steel mesh, providing both the needed retraction and a reduction in the use of individual pads. EZ DASH has been introduced into clinical use in 183 consecutive cases by specialty surgeons (colorectal, gynecology, and gynecologic oncology services) at multiple medical centers. The retractor may be shaped to the individual needs of an operating field, eg, the pelvis, and the small bowel secured behind the retractor, held in place by the tension of its mesh and the security of the abdominal wall. Positioning has been intuitive and secure, and the intraoperative use of sponges and of operating time have both been noticeably reduced. Among 183 cases, 91% of uses were felt to reduce OR time by ≤5 to ≥10 minutes. Ninety-three percent of EZ DASH cases used fewer individual laparotomy pads for small bowel retraction. Ninety-five percent of uses suggested a value added to the case by the operating surgeon with an expressed desire to use the product repeatedly. The EZ DASH is a simple method of obtaining small bowel retraction and laparotomy pad absorption with a reduction in the need for individual pads, providing excellent exposure for the operative field and reducing the risk of retained foreign body.

Statistics of the log-det estimator

The log-det estimator is a measure of divergence (evolutionary distance) between sequences of biological characters, DNA or amino acids, for example, and has been shown to be robust to biases in composition that can cause problems for other estimators. We provide a statistical framework to construct high-accuracy confidence intervals for log-det estimates and compare the efficiency of the estimator to that of maximum likelihood using time-reversible Markov models. The log-det estimator is found to have good statistical properties under such general models.

Social inequalities in health disentangling the underlying mechanisms

Differentials in health and longevity by socioeconomic status and by the nature of social relationships have been found in innumerable studies in the social and medical sciences. Three categories of explanations for the observed patterns have been proposed: causal mechanisms through which the social environment affects health status or the risk of dying; selection or reverse causal pathways whereby a person's health status affects their social position; and artifactual mechanisms, such as measurement error. The general consensus among researchers is that the observed disparities in health are driven largely by a complex set of causal processes rather than by selection or by artifactual mechanisms. This paper explores the set of arguments and strategies that researchers have used to arrive at this conclusion. As part of this undertaking, we assess whether inferences regarding the minor contribution of selection to the overall association between social factors and health are justifiable. In addition, we identify current avenues of research that are providing new insights into the causal pathways linking social factors and health.

Complete characterization of the (D2O)2 ground state: high Ka rotation-tunneling levels

We report the observation of extensive a- and c-type rotation-tunneling (RT) spectra of (D2O)2 for Ka = 0-4. These data allow quantification of molecular constants and tunneling splittings for a number of previously unobserved RT states of (D2O)2. The vibrational ground state has thus been characterized to energies as high as those of some of the intermolecular vibrations, and we present the first test of the VRT(ASP-W) potential at these high Ka states.

Molecular phylogenetics: state-of-the-art methods for looking into the past

As the amount of molecular sequence data in the public domain grows, so does the range of biological topics that it influences through evolutionary considerations. In recent years, a number of developments have enabled molecular phylogenetic methodology to keep pace. Likelihood-based inferential techniques, although controversial in the past, lie at the heart of these new methods and are producing the promised advances in the understanding of sequence evolution. They allow both a wide variety of phylogenetic inferences from sequence data and robust statistical assessment of all results. It cannot remain acceptable to use outdated data analysis techniques when superior alternatives exist. Here, we discuss the most important and exciting methods currently available to the molecular phylogeneticist.

A general empirical model of protein evolution derived from multiple protein families using a maximum-likelihood approach

Phylogenetic inference from amino acid sequence data uses mainly empirical models of amino acid replacement and is therefore dependent on those models. Two of the more widely used models, the Dayhoff and JTT models, are estimated using similar methods that can utilize large numbers of sequences from many unrelated protein families but are somewhat unsatisfactory because they rely on assumptions that may lead to systematic error and discard a large amount of the information within the sequences. The alternative method of maximum-likelihood estimation may utilize the information in the sequence data more efficiently and suffers from no systematic error, but it has previously been applicable to relatively few sequences related by a single phylogenetic tree. Here, we combine the best attributes of these two methods using an approximate maximum-likelihood method. We implemented this approach to estimate a new model of amino acid replacement from a database of globular protein sequences comprising 3,905 amino acid sequences split into 182 protein families. While the new model has an overall structure similar to those of other commonly used models, there are significant differences. The new model outperforms the Dayhoff and JTT models with respect to maximum-likelihood values for a large majority of the protein families in our database. This suggests that it provides a better overall fit to the evolutionary process in globular proteins and may lead to more accurate phylogenetic tree estimates. Potentially, this matrix, and the methods used to generate it, may also be useful in other areas of research, such as biological sequence database searching, sequence alignment, and protein structure prediction, for which an accurate description of amino acid replacement is required.

Diffusion of ideas about personal hygiene and contamination in poor countries: evidence from Guatemala

In this paper, we explore the diffusion of beliefs pertaining to the causes of childhood diarrhea in rural Guatemala. The analysis focuses on the importance of interpersonal and impersonal contacts as conduits for information and norms related to hygiene and contamination. Estimates from multivariate models reveal that there is evidence of a diffusion process through social contacts, primarily through interpersonal ones. The analysis also identifies striking differences between (1) the diffusion process related to hygiene (e.g. dirtiness) and that related to contamination (e.g. pathogens); and (2) beliefs about the causes of diarrheal illness among children in general and those among respondents' own children.

Likelihood-based tests of topologies in phylogenetics

Likelihood-based statistical tests of competing evolutionary hypotheses (tree topologies) have been available for approximately a decade. By far the most commonly used is the Kishino-Hasegawa test. However, the assumptions that have to be made to ensure the validity of the Kishino-Hasegawa test place important restrictions on its applicability. In particular, it is only valid when the topologies being compared are specified a priori. Unfortunately, this means that the Kishino-Hasegawa test may be severely biased in many cases in which it is now commonly used: for example, in any case in which one of the competing topologies has been selected for testing because it is the maximum likelihood topology for the data set at hand. We review the theory of the Kishino-Hasegawa test and contend that for the majority of popular applications this test should not be used. Previously published results from invalid applications of the Kishino-Hasegawa test should be treated extremely cautiously, and future applications should use appropriate alternative tests instead. We review such alternative tests, both nonparametric and parametric, and give two examples which illustrate the importance of our contentions.

Elevated P-selectin on platelets in depression: response to bupropion

Increased platelet activation has been suggested as a possible reason for the increased vulnerability of depressed patients to ischemic heart disease (IHD). Translocation of P-selectin, an integral alpha-granule membrane protein, to the platelet surface is a measure of platelet activation. Herein, western blots of platelet plasma membranes containing P-selectin were quantified in patients with major depression (n=19; mean age=39 +/- 2 years) and healthy comparison subjects (n=17; mean age=36 +/- 2 years). None evidenced clinical signs of IHD, and only two patients had a lifestyle IHD risk factor (smoking). Blood was obtained from all 19 depressed patients before treatment, and 15 returned after 6-8 weeks of open-label bupropion treatment. Bupropion was chosen as the antidepressant because it did not elevate plasma norepinephrine or serotonin, endogenous agonists that can induce platelet degranulation. Western blotting revealed more P-selectin immunoreactivity (75 kD band) in depressed patients compared to healthy controls (P=0.003). After bupropion treatment, P-selectin remained high in depressed patients. beta3-Integrin, a reference plasma membrane protein that does not translocate during activation, was of equivalent density in depressed patients and healthy control subjects, and was unchanged after treatment with bupropion. P-Selectin failed to correlate with severity of illness based on the Hamilton Depression scale, or with the post-treatment plasma concentration of bupropion. The results suggest an elevation in P-selectin on platelet plasma membranes might be a trait marker for depression.

Codon-Substitution Models for Heterogeneous Selection Pressure at Amino Acid Sites

Comparison of relative fixation rates of synonymous (silent) and nonsynonymous (amino acid-altering) mutations provides a means for understanding the mechanisms of molecular sequence evolution. The nonsynonymous/synonymous rate ratio (ω = dN/dS) is an important indicator of selective pressure at the protein level, with ω = 1 meaning neutral mutations, ω &lt; 1 purifying selection, and ω &gt; 1 diversifying positive selection. Amino acid sites in a protein are expected to be under different selective pressures and have different underlying ω ratios. We develop models that account for heterogeneous ω ratios among amino acid sites and apply them to phylogenetic analyses of protein-coding DNA sequences. These models are useful for testing for adaptive molecular evolution and identifying amino acid sites under diversifying selection. Ten data sets of genes from nuclear, mitochondrial, and viral genomes are analyzed to estimate the distributions of ω among sites. In all data sets analyzed, the selective pressure indicated by the ω ratio is found to be highly heterogeneous among sites. Previously unsuspected Darwinian selection is detected in several genes in which the average ω ratio across sites is &lt;1, but in which some sites are clearly under diversifying selection with ω &gt; 1. Genes undergoing positive selection include the β-globin gene from vertebrates, mitochondrial protein-coding genes from hominoids, the hemagglutinin (HA) gene from human influenza virus A, and HIV-1 env, vif, and pol genes. Tests for the presence of positively selected sites and their subsequent identification appear quite robust to the specific distributional form assumed for ω and can be achieved using any of several models we implement. However, we encountered difficulties in estimating the precise distribution of ω among sites from real data sets.

EDIBLE: experimental design and information calculations in phylogenetics

Although evolutionary inference from molecular sequences is a statistical problem, little attention has been paid to questions of experimental design. A computer program, EDIBLE, has been developed to perform likelihood calculations based on Markov process models of nucleotide substitution allied with phylogenetic trees, and from these to compute Fisher information measures under different experimental designs. These calculations can be used to answer questions of optimal experimental design in molecular phylogenetics.

AVAILABILITY

Source code (ANSI C), executables and documentation for EDIBLE are available from http://ng-dec1.gen.cam. ac.uk/info/index.htmland 'downstream' Web pages.

CONTACT

N.Goldman@gen.cam.ac.uk

Health-seeking behaviour for child illness in Guatemala

Relying on data from the 1995 Guatemalan Survey of Family Health (EGSF), we analyse the relationship between child illness and health-seeking behaviour. Information on illness was collected for 3193 children. This analysis is based on 870 of these who became ill with diarrhoeal or respiratory disease during a 13-day period prior to interview. Estimates are derived from logistic models of the probability of seeing any or a specific type of health care provider as a function of characteristics of the illness on a given day and the child. The results indicate that modern medical care plays a major role in the treatment of infectious illness among children in rural Guatemala, with visits to pharmacists, doctors and the staff at government health facilities occurring much more frequently than visits to curers and other traditional practitioners. In general, families are much more likely to seek out a health care provider when a child experiences fever and gastrointestinal symptoms than when suffering from respiratory and other symptoms, and when a mother perceives the illness to be serious. The results also indicate that infants, low parity children, and children assessed as having generally been in good health are more likely to visit health care providers than other children. However, the particular associations often vary by type of health care provider.

A description of child illness and treatment behavior in Guatemala

This paper uses a new calendar design implemented in the Guatemalan Survey of Family Health to analyze diarrheal and respiratory illness among children. The calendar provides a much richer description of child illness and treatment behavior than do conventional data typically collected in health interview surveys. The resulting estimates reveal that Guatemalan children experience high rates of diarrheal and respiratory illness and that these illnesses often involve multiple symptoms that only partially overlap one another. In addition, estimates from the calendar demonstrate that the measurement of illness frequency is fairly complex and that classification of illness into distinct categories may not always be feasible or meaningful. Results regarding treatment behavior indicate that the vast majority of illnesses are treated and that mothers almost always receive advice regarding their children's illnesses from relatives. On the other hand, health providers are sought for advice and treatment in only about one-third of illnesses. When families do seek providers, they are more likely to rely on biomedical ones - especially pharmacists, doctors and personnel at health posts and centers - than traditional practitioners. By far, the most common form of treatment - recommended by both relatives and providers - consists of readily available Western medicines. In contrast, the use of traditional remedies appears to be relatively low.

Understanding ethnic variation in pregnancy-related care in rural Guatemala

OBJECTIVES

This study examines the relatively low use of modern pregnancy-related care in Guatemala, especially among indigenous women, and explores the role of socioeconomic status, social and cultural variables, and access to biomedical health facilities in accounting for ethnic differences in care.

METHODS

The data for the analysis come from the Guatemalan Survey of Family Health--a population-based survey of rural women that contains detailed data on care received during pregnancy and delivery along with extensive background information. Binomial and multinomial logit models are used to identify the variables that affect the likelihood of receiving different types of care during pregnancy and delivering in a medical facility and the extent to which sociocultural factors and measures of access account for the observed ethnic differences.

RESULTS

The estimates not only confirm previous findings of a large ethnic difference in the use of modern pregnancy-related care, but also extend them by identifying a gradient within the indigenous population. The analysis demonstrates that, in general, sociocultural variables are more strongly associated with modern pregnancy-related care than are measures of access and that the former variables explain more of the ethnic variation in care than the latter. The results also demonstrate that pregnant women, especially indigenous women, are more likely to seek biomedical care in conjunction with traditional midwifery care rather than to rely solely on the former.

CONCLUSION

The findings suggest that midwives are likely to continue to be key providers of pregnancy-related care in the future, even as access to modern health facilities improves. Current efforts directed toward the training and integration of midwives into the formal health system are likely to be much more effective at improving pregnancy-related care than the replacement of midwives with biomedical providers.

Do health interview surveys yield reliable data on chronic illness among older respondents?

Previous research evaluating quality of health interview survey data has generally relied upon comparisons of household interview data with medical records or other external sources of information. However, "gold standards" are not always satisfactory or available. This paper illustrates an alternative approach to the evaluation of data quality-examination of the reliability of reports of chronic conditions in longitudinal surveys. The data come from national samples of older Americans (First National Health and Nutrition Examination Survey Epidemiologic Followup Study, 1971-1975, 1982-1984, 1986) and older Taiwanese (Survey of Health and Living Status of the Elderly, 1989, 1993, 1996). The results show that, among respondents who reported a chronic condition at a given interview, the likelihood that the condition was acknowledged at the subsequent interview was higher for hypertension and diabetes than for arthritis and stroke. Low levels of consistency for stroke appear to result partly from the poor wording of questions. In Taiwan, younger, more educated persons and those experiencing severe conditions were somewhat more likely to acknowledge the condition at follow-up compared with their respective counterparts. Women and persons of high cognitive status in the United States and respondents in both countries who used a proxy to report the occurrence of a stroke were also more likely to acknowledge conditions at follow-up.