RESUMEN
In many practical scenarios, a flying insect must search for the source of an emitted cue which is advected by the atmospheric wind. On the macroscopic scales of interest, turbulence tends to mix the cue into patches of relatively high concentration over a background of very low concentration, so that the insect will detect the cue only intermittently and cannot rely on chemotactic strategies which simply climb the concentration gradient. In this work we cast this search problem in the language of a partially observable Markov decision process and use the Perseus algorithm to compute strategies that are near-optimal with respect to the arrival time. We test the computed strategies on a large two-dimensional grid, present the resulting trajectories and arrival time statistics, and compare these to the corresponding results for several heuristic strategies, including (space-aware) infotaxis, Thompson sampling, and QMDP. We find that the near-optimal policy found by our implementation of Perseus outperforms all heuristics we test by several measures. We use the near-optimal policy to study how the search difficulty depends on the starting location. We also discuss the choice of initial belief and the robustness of the policies to changes in the environment. Finally, we present a detailed and pedagogical discussion about the implementation of the Perseus algorithm, including the benefits-and pitfalls-of employing a reward-shaping function.
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Algoritmos , Olfato , Animales , Teorema de Bayes , Insectos , PolíticasRESUMEN
Magnetohydrodynamic turbulence on a ß plane with an in-plane mean field, a system which serves as a simple model for the solar tachocline, is investigated analytically and computationally. We first derive two useful analytic constraints: We express the mean turbulent cross-helicity in terms of the mean turbulent magnetic energy, and then show that (for weak turbulence) the time-averaged momentum transport in the system can be expressed in terms of the cross-helicity spectrum. We then complete a closure of the system using weak turbulence theory, appropriately extended to a system with multiple interacting eigenmodes. We use this closure to perturbatively solve for the spectra at lowest order in the Rossby parameter ß and thereby show that the momentum transport in the system is O(ß^{2}), thus quantifying the transition away from Alfvénized turbulence. Finally, we verify our theoretical results by performing direct numerical simulations of the system over a broad range of ß.
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A central problem of turbulence theory is to produce a predictive model for turbulent fluxes. These have profound implications for virtually all aspects of the turbulence dynamics. In magnetic confinement devices, drift-wave turbulence produces anomalous fluxes via cross-correlations between fluctuations. In this work, we introduce an alternative, data-driven method for parametrizing these fluxes. The method uses deep supervised learning to infer a reduced mean-field model from a set of numerical simulations. We apply the method to a simple drift-wave turbulence system and find a significant new effect which couples the particle flux to the local gradient of vorticity. Notably, here, this effect is much stronger than the oft-invoked shear suppression effect. We also recover the result via a simple calculation. The vorticity gradient effect tends to modulate the density profile. In addition, our method recovers a model for spontaneous zonal flow generation by negative viscosity, stabilized by nonlinear and hyperviscous terms. We highlight the important role of symmetry to implementation of the alternative method.
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The ion-ion dynamic structure factor of warm dense matter is determined using the recently developed pseudoatom molecular dynamics method [Starrett et al., Phys. Rev. E 91, 013104 (2015)]. The method uses density functional theory to determine ion-ion pair interaction potentials that have no free parameters. These potentials are used in classical molecular dynamics simulations. This constitutes a computationally efficient and realistic model of dense plasmas. Comparison with recently published simulations of the ion-ion dynamic structure factor and sound speed of warm dense aluminum finds good to reasonable agreement. Using this method, we make predictions of the ion-ion dynamical structure factor and sound speed of a warm dense mixture-equimolar carbon-hydrogen. This material is commonly used as an ablator in inertial confinement fusion capsules, and our results are amenable to direct experimental measurement.
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The impact of tick control on the productivity of indigenous cattle was investigated in three herds of East African shorthorn Zebu and Zebu x Ankole (Nganda) breeds, maintained under three tick management systems practised under ranch conditions: twice-a-week dipping, once-a-month dipping, and no tick control. The milk production and the growth rates of pre-weaned and post-weaned calves were monitored once a month over a period of 34 months. Milk offtake was 23% higher during the heavy rainy seasons than in the long dry seasons. Twice-a-week dipping increased the milk offtake by 21% in the second year of study and prolonged the duration of lactation in cows. Similarly, twice-a-week dipping increased the pre-weaning growth rate by 39% in the second year of study, but had no significant effect on the post-weaning growth rate. Generally, the growth rate of calves were greatest during the heavy rainy seasons and least during the long dry seasons. These results provide a basis for assessing the losses under different tick management systems in the various production systems.
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Enfermedades de los Bovinos/parasitología , Bovinos/crecimiento & desarrollo , Clorfenvinfos/administración & dosificación , Insecticidas/administración & dosificación , Lactancia/efectos de los fármacos , Compuestos Organotiofosforados , Control de Ácaros y Garrapatas/métodos , Enfermedades por Picaduras de Garrapatas/veterinaria , Garrapatas/crecimiento & desarrollo , Administración Tópica , Crianza de Animales Domésticos , Animales , Peso Corporal , Enfermedades de los Bovinos/prevención & control , Femenino , Masculino , Estaciones del Año , Enfermedades por Picaduras de Garrapatas/parasitología , Enfermedades por Picaduras de Garrapatas/prevención & control , Garrapatas/metabolismo , UgandaRESUMEN
OBJECTIVE: To evaluate the effectiveness of infant massage compared with that of a crib vibrator in the treatment of infantile colic. METHODS: Infants <7 weeks of age and perceived as colicky by their parents were randomly assigned to an infant massage group (n = 28) or a crib vibrator group (n = 30). Three daily intervention periods were recommended in both groups. Parents recorded infant crying and given interventions in a structured cry diary that was kept for 1 week before (baseline) and for 3 weeks during the intervention. Parents were interviewed after the first and third weeks of intervention to obtain their evaluation of the effectiveness of the given massage or crib vibration. RESULTS: At baseline, the mean amount of total crying was 3.6 (standard deviation: 1.4) hours/day in the massage group infants and 4.2 (2.0) hours/day in the vibrator group infants. The mean amount of colicky crying was 2.1 (standard deviation: 1.1) hours/day and 2.9 (1.5) hours/day, respectively. The mean number of daily intervention periods was 2.2 in both groups. Over the 4-week study, the amount of total and colicky crying decreased significantly in both intervention groups. The reduction in crying was similar in the study groups: total crying decreased by a mean 48% in the massage group and by 47% in the vibrator group, and colicky crying decreased by 64% and 52%, respectively. The amount of other crying (total crying minus colicky crying) remained stable in both groups over the intervention. Ninety-three percent of the parents in both groups reported that colic symptoms decreased over the 3-week intervention, and 61% of the parents in the massage group and 63% of the parents in the crib vibrator group perceived the 3-week intervention as colic reducing. CONCLUSIONS: Infant massage was comparable to the use of a crib vibrator in reducing crying in colicky infants. We suggest that the decrease of total and colicky crying in the present study reflects more the natural course of early infant crying and colic than a specific effect of the interventions.
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Cólico/terapia , Masaje , Vibración/uso terapéutico , Análisis de Varianza , Lechos , Cólico/complicaciones , Llanto , Estudios de Evaluación como Asunto , Femenino , Humanos , Lactante , Recién Nacido , Entrevistas como Asunto , Masculino , Masaje/métodos , PadresRESUMEN
Studies on seasonality and population dynamics of ticks on indigenous cattle and their crosses (calves) were carried out in Buruli Ranching Scheme, Nabiswera, Luwero district of Uganda on three treatment groups of animals: group 1 (twice a week dipping), group 2 (once a month dipping) and group 3 (no tick control). During this study, four major species of ticks of economic importance were recorded in decreasing order of abundance: Rhipicephalus appendiculatus, Rhipicephalus evertsi evertsi, Amblyomma variegatum and Boophilus decoloratus. Of these ticks, a seasonal pattern of activity was only observed in R. appendiculatus ticks, with peak activities occurring during rainy seasons. Greater numbers of ticks were recorded on cows than calves in the three treatment groups, with the exception of A. variegatum where the reverse occurred. The mean numbers of ticks per animal were highly significantly different (p < 0.01) when group 1 animals were compared with group 2 and 3 animals. However, no significant differences (p > 0.05) were observed in mean tick numbers between group 2 and 3 animals. Highly significant differences (p < 0.01) were observed in mean tick numbers on cows and calves (more than 12 months old) in different calving seasons. The state of lactation only affected tick counts on cows in group 1; significantly more ticks (p < 0.01) were observed in lactating than non-lactating cows. Furthermore, significantly greater (p < 0.05) numbers of ticks (with the exception of B. decoloratus) were recorded during the second year of study (March 1992-May 1993) than the first year (January 1991-February 1992), despite lower rainfall during the former period.
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Enfermedades de los Bovinos/parasitología , Infestaciones por Garrapatas/veterinaria , Garrapatas , Animales , Bovinos , Dinámica Poblacional , Estaciones del Año , Infestaciones por Garrapatas/parasitología , Garrapatas/clasificación , UgandaRESUMEN
A financial analysis was performed to assess the performance of three acaricide-treatment groups of indigenous breeds (Zebu and Nganda) of cattle on a ranch in Luwero District, Uganda. The treatments were based on different frequencies: twice-a-week dipping, once-a-month dipping and no tick control. The objective was to evaluate the economic justification for intensive acaricide application for tick and tick-borne disease control in Uganda. Data were collected by monitoring cattle performance over a period of 34 months. Biological data collected included the number of cows at the beginning and end of the study, net starting liveweight, number of calves born, number of animals dying due to tick-borne diseases and other causes, number of animals sold or slaughtered and milk yield. Records of variable costs (acaricides, drugs, labour, etc.) and output prices were assembled and calculated by treatment group. Gross margin and marginal analysis were used in the financial analysis. The exchange rate in 1990-1993 was one US$ to 1200 Uganda shillings. The gross benefits obtained from animal sales, herd value and milk yield were Uganda shillings 1175, 1389 and 1311 per kg of net starting liveweight for animals dipped twice-a-week, once-a-month and not dipped, respectively. The variable costs were Ug. shs. 424, 390 and 360 per kg of net starting liveweight, respectively. Consequently, the gross margins were Ug. shs. 751, 999 and 951 per kg of net starting liveweight. Furthermore, the marginal rate of return (MRR) in changing from no tick control to once-a-month dipping was 160%, while changing from no tick control to twice-a-week dipping was negative (-313%). The above results showed that the value of increased gains in production obtained from twice-a-week dipping strategy does not offset the costs of inputs for intensive dipping. Once-a-month dipping (strategic) therefore appears to be the most-profitable tick-control strategy for the farmer. The need to conduct further studies in different livestock- production systems and to rationalise future tick control policies is discussed.
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Crianza de Animales Domésticos/economía , Enfermedades de los Bovinos/prevención & control , Control de Ácaros y Garrapatas/economía , Infestaciones por Garrapatas/veterinaria , Enfermedades por Picaduras de Garrapatas/veterinaria , Administración Tópica , Crianza de Animales Domésticos/métodos , Animales , Bovinos , Enfermedades de los Bovinos/economía , Clorfenvinfos/administración & dosificación , Clorfenvinfos/economía , Clorfenvinfos/uso terapéutico , Control de Costos/métodos , Análisis Costo-Beneficio , Esquema de Medicación , Femenino , Insecticidas/administración & dosificación , Insecticidas/economía , Insecticidas/uso terapéutico , Estudios Longitudinales , Masculino , Control de Ácaros y Garrapatas/métodos , Infestaciones por Garrapatas/economía , Infestaciones por Garrapatas/prevención & control , Enfermedades por Picaduras de Garrapatas/economía , Enfermedades por Picaduras de Garrapatas/prevención & control , Garrapatas , UgandaRESUMEN
The possible effects of intense physical exercise on the total body stature of low back pain patients were monitored by circadian total body height measurements. The height was measured with a statiometer, and the change in height was correlated with the changes in the range of motion, pain and subjective disability and degree of disc degeneration seen on magnetic resonance imaging (MRI) pictures. The stature of 24 low back pain patients was measured during a 3-week period. There was an increase of about 3 mm in height after only 4 days of exercise, and by the end of the programme the morning height increased on average by 7.2 mm. There were also 12 non-rehabilitated low back pain patients but no such increase was noted among them. The gain of height and reduction of pain were found to be statistically significantly correlated (P = 0.0001, r = -0.41), as did the gain of height and the decrease of back disability (Oswestry index) (P < 0.0001, r = -0.39). Circadian total height measures but not the MR images will change due to the active back rehabilitation programme.
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Dolor de Espalda/fisiopatología , Dolor de Espalda/rehabilitación , Estatura , Ritmo Circadiano , Terapia por Ejercicio , Adulto , Agua Corporal/fisiología , Femenino , Humanos , Disco Intervertebral/fisiología , Masculino , Persona de Mediana Edad , Estudios ProspectivosAsunto(s)
Brotes de Enfermedades/veterinaria , Enfermedades de las Cabras/epidemiología , Mycoplasma/aislamiento & purificación , Pleuroneumonía Contagiosa/epidemiología , Enfermedades de las Ovejas/epidemiología , Animales , Femenino , Enfermedades de las Cabras/microbiología , Cabras , Pulmón/microbiología , Pleuroneumonía Contagiosa/microbiología , Ovinos , Enfermedades de las Ovejas/microbiología , Uganda/epidemiologíaRESUMEN
The effect of treating cattle with deltamethrin to control tsetse flies and ticks was investigated on 2 ranches 8 km apart in central Uganda where there is a high risk of trypanosomosis. This area had a moderate challenge of Glossina pallidipes. The cattle had very low challenge of Rhipicephalus appendiculatus, Amblyomma variegatum, Boophilus decolaratus and Rhipicephalus evertsi evertsi, due to regular treatment with dioxathion. On one ranch a dip was charged with deltamethrin to treat cattle regularly for 3 months. The other ranch was used as a control for the tsetse population, but the animals continued to be treated regularly with dioxathion using hand sprays. On the ranch using deltamethrin treatment a reduction of 96.9% in the tsetse population was recorded after 2 treatments at 2 week intervals. Total (100%) control of tsetse was achieved from the fourth treatment up to the end of the trial period. The ranch with dioxathion treatment experienced an overall tsetse reduction of 19.15% during the thirteenth to fifteenth weeks and the factors contributing to this are discussed. However, the mean apparent tsetse density of 4.83 flies/trap/day recorded at the control ranch was significantly different from the mean of 0.81 flies/trap/day (P < 0.001) at the ranch using deltamethrin treatment. It was difficult to assess the effect of this product on ticks because of lack of controls. However, there are indications that deltamethrin can also reduce tick populations and the incidence of tick-borne diseases. The possible limitations and practical implications associated with large scale use of this product in the country are discussed.
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Control de Insectos , Insecticidas , Piretrinas , Moscas Tse-Tse , Animales , Bovinos , Nitrilos , Infestaciones por Garrapatas/prevención & control , Garrapatas , Tripanosomiasis Bovina/prevención & control , Moscas Tse-Tse/fisiología , UgandaRESUMEN
A comprehensive 4-week inpatient treatment including intensive physical training was evaluated in 194 chronic low back pain patients of whom 101 were working and 79 were on sick leave. Physical performance was assessed by measurements of spinal mobility, isometric trunk flexion and extension strength, and isokinetic lifting strength. Outcome was evaluated by a functional capacity index and work status changes reported at a 12-month follow-up. There was a 30-50% average increase in physical performance during treatment. At the 12-month follow-up the functional capacity index showed an average increase from 35.4 to 39.3 points (score range 24-48). At follow-up 28% of the sicklisted patients had returned to work and of those employed before treatment 14% were on sick leave. Associations between outcome and the improvement in physical measurements and their level at discharge were determined by stepwise multiple and logistic regression analyses. Among the physical measurements only increase in spinal mobility was associated with functional capacity index in women and return to work in both men and women at the 12-month follow-up. The overall results showed that intensive physical training and improved physical performance did not play crucial roles in the rehabilitation of chronic low back pain patients, at least when return to work was used as the outcome criterion.
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Terapia por Ejercicio/métodos , Dolor de la Región Lumbar/rehabilitación , Educación del Paciente como Asunto , Terapia por Relajación , Adulto , Terapia Cognitivo-Conductual , Tolerancia al Ejercicio/fisiología , Femenino , Estudios de Seguimiento , Humanos , Contracción Isométrica/fisiología , Dolor de la Región Lumbar/epidemiología , Masculino , Contracción Muscular/fisiología , Análisis de Regresión , Factores de Tiempo , Resultado del TratamientoRESUMEN
We compared the results of two multimodal back treatment programs (program A: n = 134; program B: n = 175) using pain, functional capacity, sickness absence, subjective state of health, depression, and work status as outcome variables. Whereas in program A exercise was guided by pain, in program B a "no pain, no gain" rationale was used as a basis for intensive physical training. Neither of the programs included direct attempts to influence the patient's environment (i.e., to find employment or to modify working conditions). In both programs, a clear decrease in pain and an increase in functional capacity was found from the pretreatment phase to the 12-month follow-up. These changes were, however, stronger in program B. Days of absence decreased significantly in group B, but the change was not significantly different from that in group A. On the whole, the more intensive training showed somewhat better results, even though the difference was not substantial. In contrast to some earlier results, there was no statistically significant increase in the proportion of those employed after treatment in either group. The results indicate that intensive physical exercise does not, as such, solve the problem of back disability in a country that has a highly developed social security system. More active interventions in work and work-life are needed.
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Dolor de Espalda/rehabilitación , Terapia por Ejercicio , Adulto , Depresión/terapia , Evaluación de la Discapacidad , Femenino , Humanos , Masculino , Persona de Mediana Edad , TrabajoRESUMEN
Anti-yersinia antibodies were assessed in sera from 630 patients admitted to a department of surgery for acute abdominal disease, using an enzyme-linked immunosorbent assay (ELISA). In 21 patients a high concentration of yersinia antibodies confirmed recent yersinia infection. Eight patients had an appendicectomy performed; in all patients with antibodies against Y. enterocolitica 9 or Y. pseudotuberculosis IA a true appendicitis was found at operation. Two patients with Y. enterocolitica 3 antibodies had acute terminal ileitis and mesenterial lymphadenitis. In 4 patients a diagnosis of acute pancreatitis was established; 2 of these had cholecystitis. Two further patients had cholecystitis without pancreatic affection. Two patients had colonic diverticulitis, 1 with perforation. The results demonstrate that yersinia infection may commonly give rise to a variety of acute abdominal inflammations, and stress the importance of serological and bacteriological diagnostic procedures.
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Gastroenteritis/etiología , Yersiniosis/complicaciones , Enfermedad Aguda , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Apendicitis/etiología , Colecistitis/etiología , Ensayo de Inmunoadsorción Enzimática , Humanos , Inmunoglobulina A/biosíntesis , Inmunoglobulina G/biosíntesis , Inmunoglobulina M/biosíntesis , Persona de Mediana Edad , Pancreatitis/etiología , Yersiniosis/inmunología , Yersinia enterocolitica/inmunología , Yersinia pseudotuberculosis/inmunología , Infecciones por Yersinia pseudotuberculosis/complicacionesRESUMEN
Enteral feeding by nasoenteral tube was begun immediately after surgery of the alimentary tract in 120 patients. In 37 cases the feeding was delivered proximally to a fresh anastomosis or enterotomy. Immediate enteral feeding was well tolerated even after major elective surgery of the gastrointestinal tract. The feeding promoted recovery of bowel function and evoked no major complications. Abdominal discomfort and diarrhea were the most common side effects. The response was less favorable after nonelective surgery associated with intraabdominal or systemic sepsis.
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Nutrición Enteral/métodos , Enfermedades Gastrointestinales/cirugía , Nutrición Enteral/efectos adversos , Motilidad Gastrointestinal , Humanos , Factores de TiempoRESUMEN
The effect of one single dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on the antigenic structures of gastric juice glycoproteins, was studied in dogs. Antisera to glycoproteins of the fetal alimentary canal were raised. Histologic mucosal specimens and glycoprotein fractions of gastric juice which were taken from four dogs during a 15.5-month period after MNNG administration, were examined immunohistologically and by immunodiffusion for the appearance of fetal-like antigens. Fetal-like structures appeared in a stepwise manner in both the acid and neutral glycoprotein fractions of the gastric juice, and showed gradual crossreactivity between macromolecules obtained from gastric juice samples obtained during the observation period. Eight immunizations carried out using physicochemically different glycoprotein fractions of fetal canine alimentary canal mucosa, produced a similar response, thus indicating that the same antigenic structures are incorporated into all mucus glycoproteins, even though they do differ physicochemically. It is suggested that this "omnipotential" incorporation picture could also be found after exposure to MNNG and is, by its nature, typically fetal.
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Proteínas Fetales/análisis , Glicoproteínas/análisis , Lesiones Precancerosas/patología , Neoplasias Gástricas/patología , Animales , Reacciones Cruzadas , Perros , Técnica del Anticuerpo Fluorescente , Jugo Gástrico/análisis , Mucosa Gástrica/embriología , Mucosa Gástrica/patología , Histocitoquímica , Inmunodifusión , Masculino , Metilnitronitrosoguanidina/toxicidadRESUMEN
The eyelids of goats in Kenya contained several, conspicuous white cysts which were up to 1.5 mm in size. By histological and electron microscopical studies it was confirmed that these cysts belong to the genus Besnoitia.
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Apicomplexa/ultraestructura , Cabras , Infecciones Protozoarias en Animales , Animales , Tejido Conectivo/parasitología , Párpados/parasitología , Kenia , Microscopía Electrónica , Infecciones por Protozoos/parasitologíaRESUMEN
The effect of the nutritional status on postoperative impairment of the immune response was studied in adults undergoing major abdominal surgery. The immune function was evaluated by measuring in vitro the lymphocytic response to phytohaemagglutinin (PHA), concanavalin A (Con A) and the purified protein derivative of tuberculin (PPD) in whole blood cultures, and in vivo delayed skin hypersensitivity to candida, mumps, streptokinase-streptodornase and PPD. Nutritional assessment was carried out by evaluating recent weight loss, the weight for height index and by measuring the arm muscle circumference (AMC), triceps skinfold thickness (TSF), the creatinine-height index (CHI) and the serum concentration of albumin and prealbumin. The patient was considered malnourished, if at least three of these criteria were abnormal. The immune parameters were measured preoperatively, at the end of the surgery and five days after operation. Before the operation both malnourished and well-nourished patients had normal lymphocytic responses, but the malnourished patients had a slower recovery of immune responses after the operation and they had an increased number of postoperative complications. No significant differences in the incidence of anergy were observed between the well and malnourished patients pre or postoperatively.
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The histology and ultrastructure of resected pancreas from seven patients suffering from acute haemorrhagic pancreatitis were studied. Special attention was paid to necrotic acini and zymogen granules. Acinar cells in the border of necrotic and non-necrotic parenchyma contained lipid droplets, autophagic vacuoles, bundles of intermediate filaments and degenerated cell organelles, including zymogen granules, PAS-positive material derived from secretory proteins was situated in dilated acinar lumina and in the interstitium, and proved to be fibrillar in fine structure. There were thrombosed vessels and extravasated erythrocytes at the border of the parenchymal necrosis. Bundles of intermediate filaments were often the only identifiable structures in the severely necrotic acinar cells. The amount of lipid was decreased in damaged fat cells. Older fat necroses were surrounded by myofibroblasts. It was concluded that acinar and fat cells undergo concomitant necrosis in the inflamed pancreas, zymogen granules degenerate in the acinar cells at the border of necrotic and non-necrotic areas, and secretory proteins may be displaced in the interstitium outside acinar lumina. Myofibroblasts participate in the healing of autodigestive injuries.