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1.
Plant J ; 117(4): 1223-1238, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-37991980

RESUMEN

Plant species with large genomes tend to be excluded from climatically more extreme environments with a shorter growing season. Species that occupy such environments are assumed to be under natural selection for more rapid growth and smaller genome size (GS). However, evidence for this is available only for temperate organisms. Here, we study the evolution of GS in two subfamilies of the tropical family Zingiberaceae to find out whether species with larger genomes are confined to environments where the vegetative season is longer. We tested our hypothesis on 337 ginger species from regions with contrasting climates by correlating their GS with an array of plant traits and environmental variables. We revealed 16-fold variation in GS which was tightly related to shoot seasonality. Negative correlations of GS with latitude, temperature and precipitation emerged in the subfamily Zingiberoidae, demonstrating that species with larger GS are excluded from areas with a shorter growing season. In the subfamily Alpinioideae, GS turned out to be correlated with the type of stem and light requirements and its members cope with seasonality mainly by adaptation to shady and moist habitats. The Ornstein-Uhlenbeck models suggested that evolution in regions with humid climates favoured larger GS than in drier regions. Our results indicate that climate seasonality exerts an upper constraint on GS not only in temperate regions but also in the tropics, unless species with large genomes find alternative ways to escape from that constraint.


Asunto(s)
Zingiber officinale , Ecosistema , Clima , Estaciones del Año , Plantas
2.
Proc Natl Acad Sci U S A ; 116(47): 23398-23403, 2019 11 19.
Artículo en Inglés | MEDLINE | ID: mdl-31685640

RESUMEN

Message passing is a fundamental technique for performing calculations on networks and graphs with applications in physics, computer science, statistics, and machine learning, including Bayesian inference, spin models, satisfiability, graph partitioning, network epidemiology, and the calculation of matrix eigenvalues. Despite its wide use, however, it has long been recognized that the method has a fundamental flaw: It works poorly on networks that contain short loops. Loops introduce correlations that can cause the method to give inaccurate answers or to fail completely in the worst cases. Unfortunately, most real-world networks contain many short loops, which limits the usefulness of the message-passing approach. In this paper we demonstrate how to rectify this shortcoming and create message-passing methods that work on any network. We give 2 example applications, one to the percolation properties of networks and the other to the calculation of the spectra of sparse matrices.

3.
Osteoporos Int ; 31(2): 277-289, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31720722

RESUMEN

The trial compared three physiotherapy approaches: manual or exercise therapy compared with a single session of physiotherapy education (SSPT) for people with osteoporotic vertebral fracture(s). At 1 year, there were no statistically significant differences between the groups meaning there is inadequate evidence to support manual or exercise therapy. INTRODUCTION: To evaluate the clinical and cost-effectiveness of different physiotherapy approaches for people with osteoporotic vertebral fracture(s) (OVF). METHODS: >Prospective, multicentre, adaptive, three-arm randomised controlled trial. Six hundred fifteen adults with back pain, osteoporosis, and at least 1 OVF participated. INTERVENTIONS: 7 individual physiotherapy sessions over 12 weeks focused on either manual therapy or home exercise compared with a single session of physiotherapy education (SSPT). The co-primary outcomes were quality of life and back muscle endurance measured by the QUALEFFO-41 and timed loaded standing (TLS) test at 12 months. RESULTS: At 12 months, there were no statistically significant differences between groups. Mean QUALEFFO-41: - 1.3 (exercise), - 0.15 (manual), and - 1.2 (SSPT), a mean difference of - 0.2 (95% CI, - 3.2 to 1.6) for exercise and 1.3 (95% CI, - 1.8 to 2.9) for manual therapy. Mean TLS: 9.8 s (exercise), 13.6 s (manual), and 4.2 s (SSPT), a mean increase of 5.8 s (95% CI, - 4.8 to 20.5) for exercise and 9.7 s (95% CI, 0.1 to 24.9) for manual therapy. Exercise provided more quality-adjusted life years than SSPT but was more expensive. At 4 months, significant changes above SSPT occurred in endurance and balance in manual therapy, and in endurance for those ≤ 70 years, in balance, mobility, and walking in exercise. CONCLUSIONS: Adherence was problematic. Benefits at 4 months did not persist and at 12 months, we found no significant differences between treatments. There is inadequate evidence a short physiotherapy intervention of either manual therapy or home exercise provides long-term benefits, but arguably short-term benefits are valuable. TRIAL REGISTRATION: ISRCTN 49117867.


Asunto(s)
Terapia por Ejercicio , Modalidades de Fisioterapia , Fracturas de la Columna Vertebral , Anciano , Anciano de 80 o más Años , Análisis Costo-Beneficio , Terapia por Ejercicio/economía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Osteoporosis/complicaciones , Modalidades de Fisioterapia/economía , Estudios Prospectivos , Calidad de Vida , Fracturas de la Columna Vertebral/economía , Fracturas de la Columna Vertebral/terapia
4.
Epidemiol Infect ; 148: e147, 2020 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-32605670

RESUMEN

Major surgery carried out in low- and middle-income countries is associated with a high risk of surgical site infections (SSI), but knowledge is limited regarding contributory factors to such infections. This study explores factors related to patients developing an SSI in a teaching hospital in Ghana. A prospective cohort study of patients undergoing abdominal surgical procedures was conducted at Korle Bu Teaching Hospital. Patient characteristics, procedures and environmental characteristics were recorded. A 30-day daily surveillance was used to diagnose SSI, and Poisson regression analysis was used to test for association of SSI and risk factors; survival was determined by proportional hazard regression methods. We included 358 patients of which 58 (16.2%; 95% CI 12.7-20.4%) developed an SSI. The median number of door openings during an operation was 79, with 81% being unnecessary. Door openings greater than 100 during an operation (P = 0.028) significantly increased a patient's risk of developing an SSI. Such patients tended to have an elevated mortality risk (hazard ratio 2.67; 95% CI 0.75-9.45, P = 0.128). We conclude that changing behaviour and practices in operating rooms is a key strategy to reduce SSI risk.


Asunto(s)
Abdomen/cirugía , Microbiología del Aire , Infección de la Herida Quirúrgica/epidemiología , Infección de la Herida Quirúrgica/microbiología , Adulto , Femenino , Ghana/epidemiología , Hospitales de Enseñanza , Humanos , Masculino , Persona de Mediana Edad , Movimiento , Quirófanos , Estudios Prospectivos , Factores de Riesgo
5.
Osteoporos Int ; 29(4): 893-905, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29322223

RESUMEN

Timed loaded standing (TLS) is a suggested measure of back muscle endurance for people with vertebral osteoporosis. Surface electromyography revealed back muscles work harder and fatigue during TLS. The test end-point and total time were associated with back fatigue. The findings help demonstrate the concurrent validity of the TLS test. INTRODUCTION: The TLS test is suggested as a measure of back muscle endurance for patients with vertebral osteoporosis. However, to date, no study has demonstrated that TLS does measure back extensor or erector spinae (ES) muscle endurance. We used surface electromyography (sEMG) to investigate the performance of the thoracic ES muscles during TLS. METHODS: Thirty-six people with vertebral osteoporosis with a mean age of 71.6 (range 45-86) years participated. sEMG recordings were made of the ES at T3 and T12 bilaterally during quiet standing (QS) and TLS. The relative (%) change in sEMG amplitude between conditions was compared. Fatigue was evaluated by analysing the change in median frequency (MF) of the sEMG signal during TLS, and the correlation between maximal TLS time and rate of MF decline was examined. RESULTS: Activity in the ES increased significantly during TLS at all electrode locations. During TLS, the MF declined at a mean rate of -24.2% per minute (95% C.I. -26.5 to -21.9%). The MF slope and test time were strongly correlated (r2 = 0.71), and at test end, the final MF dropped to an average 89% (95% C.I. 85 to 93%) of initial MF. Twenty-eight participants (78%) reported fatigue was the main reason for stopping, and for eight (22%), it was pain. CONCLUSIONS: This study demonstrates that TLS challenges the ES muscles in the thoracic region and results in ES fatigue. Endurance time and the point at which the TLS test ends are strongly related to ES fatigue.


Asunto(s)
Músculos de la Espalda/fisiopatología , Fatiga Muscular/fisiología , Osteoporosis/fisiopatología , Columna Vertebral/fisiopatología , Anciano , Anciano de 80 o más Años , Dolor de Espalda/fisiopatología , Estudios Transversales , Electromiografía/métodos , Prueba de Esfuerzo/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Resistencia Física/fisiología , Posición de Pie , Vértebras Torácicas/fisiopatología
6.
Cleft Palate Craniofac J ; 55(3): 430-436, 2018 03.
Artículo en Inglés | MEDLINE | ID: mdl-29437520

RESUMEN

BACKGROUND: Submucous cleft palate (SMCP) is the most common form of cleft involving the posterior palate, resulting in variable degrees of velar dysfunction and speech disturbance. Although early surgical intervention is indicated for patients with true cleft palate, the indications for palatoplasty and timing of surgical intervention for patients with SMCP remain controversial. METHODS: Twenty-nine patients with SMCP were retrospectively reviewed. Patients treated with Furlow palatoplasty were dichotomized based on patient age at the time of surgical correction into early speech development and late speech development. Primary outcome measures included standardized assessments of hypernasal resonance and quantitative pre- and postoperative nasometry scores. Patients managed nonoperatively were included for comparison of early and late speech outcomes. RESULTS: Both early and late groups demonstrated improvement in qualitative assessment of hypernasal resonance following Furlow palatoplasty. Early and late groups also had significant improvement in pre- to postoperative nasometry scores from 7.4 to 2.3 SD from norm ( P = .01) and 6.0 to 3.6 SD from norm ( P = .02), respectively. There was no difference in postoperative nasometry scores between early and late groups, 2.3 and 3.6 SD ( P = .12). CONCLUSION: Furlow palatoplasty significantly improves the degree of hypernasality in patients with SMCP based on pre- and postoperative nasometry scores and on qualitative assessment of hypernasality. There were no differences in speech outcomes based on early compared with late operative intervention. Therefore, early palatal repair is not obligatory for optimal speech outcomes in children with SMCP and palatoplasty should be deferred until the emergence of overt velopharyngeal insufficiency.


Asunto(s)
Fisura del Paladar/cirugía , Procedimientos de Cirugía Plástica/métodos , Niño , Preescolar , Comorbilidad , Femenino , Humanos , Lactante , Tiempo de Internación/estadística & datos numéricos , Masculino , Michigan , Complicaciones Posoperatorias , Estudios Retrospectivos , Inteligibilidad del Habla , Factores de Tiempo , Resultado del Tratamiento
7.
Phys Chem Chem Phys ; 19(7): 5246-5253, 2017 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-28149993

RESUMEN

The key challenges for perovskite solar cells include their poor stability and film homogeneity. Studying the degradation and homogeneity of perovskite layers within device structures can be challenging but critical to the understanding of stability and effect of processing in real life conditions. We show that Raman spectroscopy (RS) is a unique and powerful method (simple and fast) to probe the degradation of the perovskite film within the device structure and image perovskite formation. We demonstrate that RS can be used to directly probe chemical (PbI2) and physical (dihydrated phase) degradation of a perovskite film, and estimate the relative amount of the degradation species formed, mapping its distribution with ∼1 µm spatial resolution. This has been applied to mapping a large area perovskite module to characterise the efficacy of PbI2 to perovskite conversion. We also use RS to study the degradation species and kinetics under diverse accelerated degradation conditions (temperature and humidity) in situ. These capabilities are difficult to achieve with other methods, presenting RS as an important tool to gain understanding of the degradation and effect of processing on perovskite-based photovoltaic devices.

8.
J Reconstr Microsurg ; 33(4): 298-304, 2017 May.
Artículo en Inglés | MEDLINE | ID: mdl-28201829

RESUMEN

Background Autologous breast reconstruction has been noted in the literature to provide superior aesthetic outcomes and patient satisfaction. Additionally, free perforator flap tissue transfer has the potential for lower abdominal donor site morbidity. However, it has been noted that the percentage of women who are undergoing autologous breast reconstruction in the United States is decreasing. Factors related to the technical difficulty, prolonged operative times, and decreasing reimbursement have been implicated as the causes. Methods A retrospective review of electronic medical records over a 5-year period was performed with evaluation of 77 autologous breast reconstructions at a single institution. Patient demographics, comorbidities, number of surgeons involved, operative times, length of stay, and postoperative complications were measured. Wilcoxon rank-sum, Pearson's chi-squared, and proportional odds likelihood ratio tests were performed to compare continuous, categorical, and ordinal outcomes, respectively. Propensity score weighting was used to adjust for presurgical covariates and laterality. Results Operative time and length of stay were both significantly lower in the two- versus the single-microsurgeon groups in the unadjusted setting. When covariates and laterality were adjusted for, operative times still remained significantly shorter in the two-microsurgeon group; there were no differences in complications. Conclusion Based on our findings, we propose that the two-microsurgeon approach can be utilized in more time-consuming microsurgical cases, such as autologous breast reconstruction, to safely decrease operative times and potentially alleviate surgeon fatigue, reduce operative costs, and thus increase overall surgeon productivity.


Asunto(s)
Neoplasias de la Mama/cirugía , Colgajos Tisulares Libres/irrigación sanguínea , Mamoplastia/métodos , Mastectomía/métodos , Microcirugia , Colgajo Perforante/irrigación sanguínea , Complicaciones Posoperatorias/cirugía , Estética , Femenino , Humanos , Microcirugia/métodos , Persona de Mediana Edad , Tempo Operativo , Satisfacción del Paciente/estadística & datos numéricos , Recto del Abdomen/trasplante , Estudios Retrospectivos , Trasplante Autólogo , Resultado del Tratamiento
9.
Phys Rev Lett ; 117(7): 078301, 2016 Aug 12.
Artículo en Inglés | MEDLINE | ID: mdl-27564002

RESUMEN

Community detection, the division of a network into dense subnetworks with only sparse connections between them, has been a topic of vigorous study in recent years. However, while there exist a range of effective methods for dividing a network into a specified number of communities, it is an open question how to determine exactly how many communities one should use. Here we describe a mathematically principled approach for finding the number of communities in a network by maximizing the integrated likelihood of the observed network structure under an appropriate generative model. We demonstrate the approach on a range of benchmark networks, both real and computer generated.

10.
Epidemiol Infect ; 144(15): 3288-3299, 2016 11.
Artículo en Inglés | MEDLINE | ID: mdl-27334298

RESUMEN

Poultry are possible sources of non-typhoidal Salmonella serovars which may cause foodborne human disease. We conducted a cross-sectional study to determine the prevalence of Salmonella serovars in egg-laying hens and broilers at the farm level and their susceptibility to antimicrobials commonly used in the poultry industry in Ghana. Sampling of faeces by a sock method (n = 75), dust (n = 75), feed (n = 10) and drinking water (n = 10) was performed at 75 commercial egg-laying and broiler farms in two regions of Ghana and skin neck (n = 30) at a local slaughterhouse from broilers representing different flocks. Salmonella was detected in 94/200 (47%) samples with an overall flock prevalence of 44·0%. Sixteen different serovars were identified with S. Kentucky (18·1%), S. Nima (12·8%), S. Muenster (10·6%), S. Enteritidis (10·6%) and S. Virchow (9·6 %) the most prevalent types. The predominant phage type of S. Enteritidis was PT1. All strains were susceptible to cefotaxime, ceftazidime and cefoxitin. Fifty-seven (60·6%) strains were resistant to one or more of the remaining nine antimicrobials tested by disk diffusion, of which 23 (40·4%) showed multi-resistance (resistance to ⩾3 classes of antimicrobials). Of the resistant strains (n = 57), the most significant were to nalidixic acid (89·5%), tetracycline (80·7%), ciprofloxacin (64·9%), sulfamethazole (42·1%), trimethoprim (29·8%) and ampicillin (26·3%). All S. Kentucky strains were resistant to more than two antimicrobials and shared common resistance to nalidixic acid or ciprofloxacin and tetracycline, often in combinations with other antimicrobials. PFGE analysis using XbaI of S. Kentucky demonstrated one dominant clone in the country. In conclusion, poultry produced in Ghana has a high prevalence of multi-resistant Salmonella and the common finding of clonal S. Kentucky in the Kumasi area warrants further investigations into the epidemiology of this serovar. There is an urgent need for surveillance and control programmes on Salmonella and use of antimicrobials in the Ghanaian poultry industry to protect the health of consumers.


Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana Múltiple , Enfermedades de las Aves de Corral/epidemiología , Salmonelosis Animal/epidemiología , Salmonella/aislamiento & purificación , Animales , Pollos , Estudios Transversales , Electroforesis en Gel de Campo Pulsado/veterinaria , Femenino , Ghana/epidemiología , Pruebas de Sensibilidad Microbiana/veterinaria , Enfermedades de las Aves de Corral/microbiología , Prevalencia , Salmonella/genética , Salmonelosis Animal/microbiología , Serogrupo
11.
Intern Med J ; 46(2): 148-57, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-26899887

RESUMEN

Over the past decade, the clinical spectrum of autoimmune encephalitis has expanded with the emergence of several new clinicopathological entities. In particular, autoimmune encephalitis has recently been described in association with antibodies to surface receptors and ion channels on neurological tissues. Greater clinician awareness has resulted in autoimmune encephalitis being increasingly recognised in patients with unexplained neurological and psychiatric symptoms and signs. The clinical spectrum of presentations, as well as our understanding of disease mechanisms and treatment regimens, is rapidly developing. An understanding of these conditions is important to all subspecialties of Internal Medicine, including neurology and clinical immunology, psychiatry, intensive care and rehabilitation medicine. This review provides a contemporary overview of the aetiology, investigations and treatment of the most recently described autoimmune encephalitides.


Asunto(s)
Autoanticuerpos/inmunología , Encefalitis/diagnóstico , Encefalitis/inmunología , Enfermedad de Hashimoto/diagnóstico , Enfermedad de Hashimoto/inmunología , Animales , Autoanticuerpos/sangre , Encefalopatías/sangre , Encefalopatías/diagnóstico , Encefalopatías/inmunología , Encefalitis/sangre , Enfermedad de Hashimoto/sangre , Humanos , Receptores de N-Metil-D-Aspartato/inmunología
12.
Heart Lung Circ ; 25(12): 1240-1244, 2016 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-27423976

RESUMEN

BACKGROUND: Massive pulmonary embolism is a poorly tolerated condition. Treatment options in this condition include anticoagulation and primary reperfusion therapy - systemic thrombolysis, catheter based treatments or surgical embolectomy. There is little data on the relative efficacy of each treatment. METHODS: The preoperative characteristics and outcomes of patients referred for surgical embolectomy between 2000-2014 was reviewed. Echocardiography was performed in the majority of patients before and after surgery. RESULTS: Thirty-seven patients underwent pulmonary embolectomy between 2000-2014. One patient died within 30 days, another before leaving hospital. All other patients were alive at the time of follow-up (survival 94.6% at median 36 months). Median ventilation time was 24hours. Median hospital length of stay was 10.5 days. There was echocardiographic evidence of severe right ventricular strain (increased size and decreased function) before surgery, which was significantly improved to within the normal range by discharge, and follow-up. CONCLUSIONS: Surgical embolectomy is a safe procedure, with low mortality, improved postoperative right ventricular function and pulmonary pressure, and good long-term outcome. Early relief of a large proportion of the clot burden can be life-saving. There should be consideration for its use as an initial treatment strategy in patients with massive or submassive pulmonary embolus with a large burden of proximal clot. A multidisciplinary approach for the treatment of these patients is required.


Asunto(s)
Ecocardiografía , Embolectomía , Tiempo de Internación , Embolia Pulmonar , Adulto , Cuidados Posteriores , Anciano , Supervivencia sin Enfermedad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Embolia Pulmonar/diagnóstico por imagen , Embolia Pulmonar/cirugía
13.
Phys Rev Lett ; 115(8): 088701, 2015 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-26340218

RESUMEN

A substantial volume of research is devoted to studies of community structure in networks, but communities are not the only possible form of large-scale network structure. Here, we describe a broad extension of community structure that encompasses traditional communities but includes a wide range of generalized structural patterns as well. We describe a principled method for detecting this generalized structure in empirical network data and demonstrate with real-world examples how it can be used to learn new things about the shape and meaning of networks.

14.
AIDS Res Ther ; 12: 14, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-25937825

RESUMEN

BACKGROUND: Little evidence exists on the connections between nutrition, diet intake, and quality of life (QoL) among people living with HIV (PLHIV). The study aimed to estimate the prevalence of under-nutrition among PLHIV in Nepal, and identify risk factors and assess correlations with PLHIVs' QoL and nutritional status. METHODS: This quantitative cross-sectional study used Body Mass Index (BMI) as an indicator for nutritional status, and additional information on opportunistic infections (OIs), CD4 count, and World Health Organization (WHO) clinical staging was collected from medical records. Participants were asked to complete surveys on food security and QoL. Descriptive analysis was used to estimate the prevalence of under nutrition. To assess associations between nutrition status and independent variables, bivariate and multivariate analysis was completed. Spearman's rank correlation test was used to assess the association between nutritional status and QoL. RESULTS: One in five PLHIVs was found to be under nourished (BMI <18.5 kg/m(2)). Illiteracy, residence in care homes, CD4 cells count <350 cells/mm(3), OIs, and illness at WHO clinical stages III and IV were found to be significant predictors of under nutrition. BMI was significantly correlated with three domains of QoL (psychological, social and environmental). CONCLUSION: Nutrition interventions should form an integral part of HIV care programs. Understanding the presence of OI, decline in CD4 count, and advancing WHO clinical stages as risk factors can be helpful in preventing under nutrition from developing. Longitudinal research is necessary to further explicate associations between nutritional status and QoL.

15.
BMC Health Serv Res ; 15: 344, 2015 Aug 27.
Artículo en Inglés | MEDLINE | ID: mdl-26307265

RESUMEN

BACKGROUND: Bangladesh is a highly populous country with three-quarters rural population. Pressing national shortages in health professionals has resulted in high vacancy rates in rural areas. These are compounded by excessive absenteeism and low retention among nurses and doctors posted to rural locations. This study attempts to ascertain reasons for providers' reluctance to work in rural and remote areas and to identify ways in which these barriers to appropriate staffing might be resolved. METHODS: This is a qualitative study based on in-depth interviews with healthcare providers (n = 15) and facility managers (n = 4) posted in rural areas, and key informant interviews with health policymakers at the national level (n = 2). Interview guides were written in English and translated and administered in Bengali. The collected data were re-translated and analyzed in English. Braun and Clarke's thematic analysis approach (data familiarization, coding, identifying and reviewing themes, and producing a final report) was used. RESULTS: Participants reported poor living conditions in rural areas (e.g., poor housing facilities and unsafe drinking water); overwhelming workloads with poor safety and insufficient equipment; and a lack of opportunities for career development, and skill enhancement. They reported insufficient wages and inadequate opportunities for private practice in rural areas. Managers described their lack of sufficient authority to undertake disciplinary measures for absenteeism. They also pointed at the lack of fairness in promotion practices of the providers. Policymakers acknowledged unavailability or insufficient allowances for rural postings. There is also a lack of national policy on rural retention. CONCLUSIONS: The findings revealed a complex interplay of factors influencing doctors' and nurses' availability in rural and remote public health facilities from the perspective of different players in the healthcare delivery system of Bangladesh. In addition, the study generated several possibilities for improvement, including increased allowances and incentives for rural posting; a transparent and fair promotion system for serving in rural areas; enhanced authority of the local managers for reducing worker absenteeism; and improved national policies on rural retention.


Asunto(s)
Enfermeras y Enfermeros , Lealtad del Personal , Médicos , Servicios de Salud Rural , Bangladesh , Atención a la Salud , Femenino , Humanos , Entrevistas como Asunto , Masculino , Investigación Cualitativa , Población Rural , Salarios y Beneficios , Recursos Humanos , Carga de Trabajo
16.
Phys Rev Lett ; 113(20): 208702, 2014 Nov 14.
Artículo en Inglés | MEDLINE | ID: mdl-25432059

RESUMEN

We study percolation on networks, which is used as a model of the resilience of networked systems such as the Internet to attack or failure and as a simple model of the spread of disease over human contact networks. We reformulate percolation as a message passing process and demonstrate how the resulting equations can be used to calculate, among other things, the size of the percolating cluster and the average cluster size. The calculations are exact for sparse networks when the number of short loops in the network is small, but even on networks with many short loops we find them to be highly accurate when compared with direct numerical simulations. By considering the fixed points of the message passing process, we also show that the percolation threshold on a network with few loops is given by the inverse of the leading eigenvalue of the so-called nonbacktracking matrix.

17.
Nature ; 453(7191): 98-101, 2008 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-18451861

RESUMEN

Networks have in recent years emerged as an invaluable tool for describing and quantifying complex systems in many branches of science. Recent studies suggest that networks often exhibit hierarchical organization, in which vertices divide into groups that further subdivide into groups of groups, and so forth over multiple scales. In many cases the groups are found to correspond to known functional units, such as ecological niches in food webs, modules in biochemical networks (protein interaction networks, metabolic networks or genetic regulatory networks) or communities in social networks. Here we present a general technique for inferring hierarchical structure from network data and show that the existence of hierarchy can simultaneously explain and quantitatively reproduce many commonly observed topological properties of networks, such as right-skewed degree distributions, high clustering coefficients and short path lengths. We further show that knowledge of hierarchical structure can be used to predict missing connections in partly known networks with high accuracy, and for more general network structures than competing techniques. Taken together, our results suggest that hierarchy is a central organizing principle of complex networks, capable of offering insight into many network phenomena.


Asunto(s)
Algoritmos , Modelos Biológicos , Probabilidad , Vías Biosintéticas , Cadena Alimentaria , Redes Reguladoras de Genes , Redes y Vías Metabólicas , Unión Proteica , Sensibilidad y Especificidad , Conducta Social
18.
J Dairy Sci ; 97(5): 2669-79, 2014 May.
Artículo en Inglés | MEDLINE | ID: mdl-24630648

RESUMEN

The objective of this study was to assess the relationships among temperature, moisture, carbon-to-nitrogen (C:N) ratio, space per cow, and bacterial counts from bedding material collected from compost bedded pack (CBP) barns. A field survey of 42 routinely aerated CBP barns was conducted in Kentucky between October 2010 and March 2011. Two bedding material samples of 1,064.7 cm(3) each were collected during a single site visit from 9 evenly distributed locations throughout each barn and thoroughly mixed to create a composite sample representative of the entire CBP. Bacterial counts were determined for coliforms, Escherichia coli, streptococci, staphylococci, and Bacillus spp. University of Kentucky Regulatory Services (Lexington) laboratory personnel performed nutrient analyses to determine moisture, carbon, and nitrogen contents. Surface and 10.2-cm pack depth temperatures were collected for each of the 9 evenly distributed locations and the mean calculated to produce a composite temperature. Space per cow was calculated as the total CBP area divided by number of cows housed on the CBP. The GLM procedure of SAS (SAS Institute Inc., Cary, NC) generated models to describe factors affecting bacterial counts. Bacterial counts were 6.3 ± 0.6, 6.0 ± 0.6, 7.2 ± 0.7, 7.9 ± 0.5, and 7.6 ± 0.5 log 10 cfu/g of dry matter for coliform, Escherichia coli, streptococci, staphylococci, and Bacillus spp., respectively. Composite temperature, CBP moisture, C:N ratio, and space per cow had no effect on coliform counts. Escherichia coli reached a peak concentration when the C:N ratio was between 30:1 and 35:1. Staphylococci counts increased as ambient temperature increased. Streptococci counts decreased with increased space per cow and composite temperature and increased with increasing ambient temperature and moisture. Streptococci counts peaked at a C:N ratio ranging from 16:1 to 18:1. Bacillus spp. counts were reduced with increasing moisture, C:N ratio, and ambient temperature. Mastitis-causing bacteria thrive in similar conditions to that of composting bacteria and microbes, making elimination of these at higher temperatures (55 to 65°C) difficult in an active composting environment. Producers must use recommended milking procedures and other preventative practices to maintain low somatic cell count in herds with a CBP barn.


Asunto(s)
Carga Bacteriana , Bovinos/fisiología , Vivienda para Animales , Suelo , Animales , Bacillus , Carbono/análisis , Recuento de Células , Industria Lechera/métodos , Escherichia coli , Femenino , Humedad , Kentucky , Leche/citología , Leche/microbiología , Nitrógeno/análisis , Suelo/química , Microbiología del Suelo , Staphylococcus , Streptococcus , Temperatura
19.
Plant Dis ; 98(7): 864-875, 2014 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30708845

RESUMEN

Existing crop monitoring programs determine the incidence and distribution of plant diseases and pathogens and assess the damage caused within a crop production region. These programs have traditionally used observed or predicted disease and pathogen data and environmental information to prescribe management practices that minimize crop loss. Monitoring programs are especially important for crops with broad geographic distribution or for diseases that can cause rapid and great economic losses. Successful monitoring programs have been developed for several plant diseases, including downy mildew of cucurbits, Fusarium head blight of wheat, potato late blight, and rusts of cereal crops. A recent example of a successful disease-monitoring program for an economically important crop is the soybean rust (SBR) monitoring effort within North America. SBR, caused by the fungus Phakopsora pachyrhizi, was first identified in the continental United States in November 2004. SBR causes moderate to severe yield losses globally. The fungus produces foliar lesions on soybean (Glycine max) and other legume hosts. P. pachyrhizi diverts nutrients from the host to its own growth and reproduction. The lesions also reduce photosynthetic area. Uredinia rupture the host epidermis and diminish stomatal regulation of transpiration to cause tissue desiccation and premature defoliation. Severe soybean yield losses can occur if plants defoliate during the mid-reproductive growth stages. The rapid response to the threat of SBR in North America resulted in an unprecedented amount of information dissemination and the development of a real-time, publicly available monitoring and prediction system known as the Soybean Rust-Pest Information Platform for Extension and Education (SBR-PIPE). The objectives of this article are (i) to highlight the successful response effort to SBR in North America, and (ii) to introduce researchers to the quantity and type of data generated by SBR-PIPE. Data from this system may now be used to answer questions about the biology, ecology, and epidemiology of an important pathogen and disease of soybean.

20.
Epilepsy Behav ; 29(1): 13-8, 2013 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-23911354

RESUMEN

The aims of the study were to characterize the magnitude of clearance changes during pregnancy for multiple antiepileptic drugs (AEDs) and to assess seizure frequency and factors increasing seizure risk in pregnant women with epilepsy. A retrospective analysis was performed for 115 pregnancies in 95 women with epilepsy followed at the Emory Epilepsy Center between 1999 and 2012. Antiepileptic drug blood levels (ABLs) obtained during routine clinical practice were used to calculate AED clearance at multiple points during pregnancy. Antiepileptic drug doses and seizure activity were also recorded. The data were analyzed for changes in clearance and dose across pregnancy and for an association between ABL and changes in seizure frequency. Significant changes in clearance during pregnancy were observed for lamotrigine (p<0.001) and levetiracetam (p<0.006). Average peak clearance increased by 191% for lamotrigine and 207% for levetiracetam from nonpregnant baseline. Marked variance was present across individual women and also across repeat pregnancies in individual women. Despite increased AED dose across most AEDs, seizures increased in 38.4% of patients during pregnancy. Seizure deterioration was significantly more likely in patients with seizures in the 12 months prior to conception (p<0.001) and those with localization-related epilepsy (p=0.005). When ABL fell >35% from preconception baseline, seizures worsened significantly during the second trimester when controlling for seizure occurrence in the year prior to conception. Substantial pharmacokinetic changes during pregnancy occur with multiple AEDs and may increase seizure risk. Monitoring of AED serum concentrations with dose adjustment is recommended in pregnant women with epilepsy. Further studies are needed for many AEDs.


Asunto(s)
Anticonvulsivantes/farmacocinética , Anticonvulsivantes/uso terapéutico , Epilepsia/tratamiento farmacológico , Adolescente , Adulto , Análisis de Varianza , Femenino , Humanos , Embarazo , Complicaciones del Embarazo/tratamiento farmacológico , Trimestres del Embarazo/sangre , Trimestres del Embarazo/efectos de los fármacos , Estudios Retrospectivos , Adulto Joven
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