Skyrmion transport and annihilation in funnel geometries.

Using atomistic simulations, we have investigated the transport and annihilation of skyrmions interacting with a funnel array under a current applied perpendicular to the funnel axis. We find that transport without annihilation is possible at low currents, when the motion is dominated by skyrmion-skyrmion interactions and skyrmions push each other through the funnel opening. Skyrmion annihilation occurs for higher currents when skyrmions in the upper half of the sample exert pressure on skyrmions in the bottom half of the sample due to the external current. Upon interacting with the funnel wall, the skyrmions undergo a size reduction that makes it easier for them to pass through the funnel opening. We find five phases as a function of the applied current and the size of the funnel opening: (i) pinned, (ii) transport without annihilation, (iii) transport with annihilation, (iv) complete annihilation, and (v) a reentrant pinning phase that only occurs for very narrow openings. Our findings provide insight into how to control skyrmion transport using funnel arrays by delineating regimes in which transport of skyrmions is possible as well as the conditions under which annihilation occurs.

Magnus induced diode effect for skyrmions in channels with periodic potentials.

Using a particle based model, we investigate the skyrmion dynamical behavior in a channel where the upper wall contains divots of one depth and the lower wall contains divots of a different depth. Under an applied driving force, skyrmions in the channels move with a finite skyrmion Hall angle that deflects them toward the upper wall for -xdirection driving and the lower wall for +xdirection driving. When the upper divots have zero height, the skyrmions are deflected against the flat upper wall for -xdirection driving and the skyrmion velocity depends linearly on the drive. For +xdirection driving, the skyrmions are pushed against the lower divots and become trapped, giving reduced velocities and a nonlinear velocity-force response. When there are shallow divots on the upper wall and deep divots on the lower wall, skyrmions get trapped for both driving directions; however, due to the divot depth difference, skyrmions move more easily under -xdirection driving, and become strongly trapped for +xdirection driving. The preferred -xdirection motion produces what we call a Magnus diode effect since it vanishes in the limit of zero Magnus force, unlike the diode effects observed for asymmetric sawtooth potentials. We show that the transport curves can exhibit a series of jumps or dips, negative differential conductivity, and reentrant pinning due to collective trapping events. We also discuss how our results relate to recent continuum modeling on a similar skyrmion diode system.

Espasmo hemifacial: experiencia en un centro terciario

Resumen El espasmo hemifacial consiste en un infrecuente trastorno del movimiento que afecta a la musculatura inervada por el nervio facial, en especial la de la hemicara superior. Existen dos formas clínicas, una primaria en la que la causa subyacente está representada por un conflicto neurovascular, y una secundaria, en la que la alteración del nervio facial es producida por algún tipo de lesión ocupante de espacio. Resulta de especial interés para el otorrinolaringólogo conocer esta entidad y ser capaz de diferenciar ambas formas clínicas dado el diferente enfoque terapéutico que pueden requerir. Aportamos una visión general de esta patología repasando su epidemiología y fisiopatología, además, de nuestra experiencia en forma de una serie de cuatro casos que ilustran las variadas formas de presentación de esta entidad, así como los signos y síntomas de alarma que pueden ayudar a realizar un correcto diagnóstico y manejo.

Abstract Hemifacial spasm consists of an unfrecuent movement disorder involving facial muscles, especially those from the upper half of the face. Two different clinical presentations are described. Primary hemifacial spasm is defined by a neurovascular conflict, and secondary occurs when facial nerve is damaged by a space occupying lesion. It is of special interest for the otorhinolaryngologist to get to know about this condition and to be able to acknowledge its clinical presentations due to the different therapeutical approach that may be needed for each of them. We contribute with a general vision of this entity reviewing its epidemiology and patophysiology. Furthermore, we show our experience by sharing a four-case series which we believe to illustrate the different ways of presentation as well as the alarm signs and symptoms that may be helpful in order to accomplish an accurate diagnose and treatment.

Directional locking and the influence of obstacle density on skyrmion dynamics in triangular and honeycomb arrays.

We numerically examine the dynamics of a single skyrmion driven over triangular and honeycomb obstacle arrays at zero temperature. The skyrmion Hall angleθsk, defined as the angle between the applied external drive and the direction of the skyrmion motion, increases in quantized steps or continuously as a function of the applied drive. For the obstacle arrays studied in this work, the skyrmion exhibits two main directional locking angles ofθsk= -30° and -60°. We show that these directions are privileged due to the obstacle landscape symmetry, and coincide with channels along which the skyrmion may move with few or no obstacle collisions. Here we investigate how changes in the obstacle density can modify the skyrmion Hall angles and cause some dynamic phases to appear or grow while other phases vanish. This interesting behavior can be used to guide skyrmions along designated trajectories via regions with different obstacle densities. For fixed obstacle densities, we investigate the evolution of the lockedθsk= -30° and -60° phases as a function of the Magnus force, and discuss possibilities for switching between these phases using topological selection.

Local infiltration of gonyautoxin is safe and effective in treatment of chronic tension-type headache.

BACKGROUND: Gonyautoxin are phycotoxins, whose molecular mechanism of action is a reversible block of the voltage-gated sodium channels at axonal level, impeding nerve impulse propagation. OBJECTIVE: To evaluate clinical efficacy of gonyautoxin in the treatment of patients with chronic tensional-type headache. METHODS: Open trial from September 2004 to 2005 in Hospital Clínico Universidad de Chile. Twenty-seven patients with chronic tension-type headache were locally infiltrated with gonyautoxins (50 micrograms) in ten sites considered as pain trigger points in a fixed infiltration protocol. In each site, a volume of 200 microlitres was injected. EMG recording was performed before and immediately after infiltrations. Main outcome measures are where a significantly drop-off in acute headache pain score occurs and number of days without headache pain. RESULTS: No side effects were detected in the follow-up period. From base line of 2 weeks, 19 patients of 27 (70%) are the successfully responders to the treatment. They showed the remarkable immediate effect after infiltration demonstrated by trapezium EMG recording. Patients reported a fall in pain score 5 minutes post-injection from 5.0 +/- 2.8 to 1.6 +/- 1.6 (mean +/- SD). The responder showed an average of 8.1 +/- 9.9 weeks of headache pain-free, all of them without a second infiltration or use of any additional analgesic medication. DISCUSSION: The therapeutic properties of gonyautoxin local infiltration in chronic tension-type headache patients are shown to be safe and effective. This report describes a new therapy for chronic tension-type headache involving local infiltrations of gonyautoxins. The immediate headache pain relief effect shown only minutes after toxin infiltrations were the most remarkable feature of this protocol. This is the first gonyautoxins testing report in the treatment of chronic tension-type headache.

Ceguera secundaria a neuropatía óptica isquémica por una disección carotídea espontánea. Caso clínico / Blindness caused by an ischemic optic neuropathy by spontaneous carotid dissection. Report of a case

In young and middle age subjects, spontaneous carotid dissection is an increasingly recognized cause of ischemic stroke. Their usual presentation is facial pain with a Horner syndrome and a contra lateral paresis. Blindness has been reported as a presenting symptom in only a few cases. We report a 50 years old man who presented with amblyopia in the left eye, without periocular pain. Fundoscopy showed papilledema and a peripapillar hemorrhage, compatible with an ischemic optic neuropathy. A magnetic resonance angiography confirmed a left carotid dissection.

Estudio de biodisponibilidad comparativa de dos formulaciones de risperidona existentes en el mercado chileno / Comparative bioavailability study of two formulations of risperidone available in the Chilean market

BACKGROUND: Bioavailability of a particular drug can vary according to the formulation used. Therefore, studies of comparative bioavailability of different formulations of a same drug are worthwhile. AIM: To compare the bioavailability of two risperidone formulations available in the Chilean market. MATERIAL AND METHODS: The bioavailability of a local risperidone formulation (Spiron) was compared with the original formulation of the drug (Risperdal) in 12 healthy volunteers, aged 19 +/- 1 years. A single dose of 3 mg was given orally, using a randomized double blind protocol in two periods. Fifteen blood samples were obtained at regular intervals, until 24 h after drug administration. Risperidone plasma levels were measured by high pressure liquid chromatography. pharmacokinetic parameters were calculated using a computer program that is independent of compartmental analysis. RESULTS: The area under the curve of plasma concentration versus time, from 0 to infinite (ABC0-infinity) and from 0 to 24 h (ABC0-24), early exposure (ABC from 0 to maximal time) and maximal plasma concentrations were significantly lower for Spiron. Half life time and time to achieve the maximal concentration were similar for the two formulations. CONCLUSIONS: According to bioequivalence tests suggested by the Food and Drug Administration (FDA) of the United States (90 per cent confidence interval for the difference of long transformed mean pharmacokinetic parameters), the formulations Risperdal and Spiron, cannot be considered interchangeable.

Calcificaciónestriato-pálido-dentada bilateral. Presentación en la forma dedistonía del habla / Bilateral striopallidodentate calcinosis. A speech dystonia presentation

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[Prevalence of carotid atherosclerosis in patients with cerebrovascular occlusive disease]. / Prevalencia de la ateromatosis carotídea en pacientes con enfermedad cerebro vascular oclusiva.

BACKGROUND: Hispanics have a greater incidence of stroke and prevalence of intracranial atherosclerosis than whites. AIM: To study the prevalence of extracranial atherosclerosis among patients admitted to a hospital with an ischemic stroke. MATERIAL AND METHODS: A prospective study in stroke patients admitted to a Neurology ward in a University Hospital. All were subjected to a CT scan, carotid duplex-Doppler ultrasonographic examination with Doppler measurement of blood flow velocity, permeability and plaques. Cardiac emboli were searched with transthoracic and transesophageal echocardiography. RESULTS: One hundred ten patients (39 women), aged 67.5 +/- 11.4 years old were studied. Stroke was atherothrombotic in 46 (41.8%), embolic in 30 (27.3%), lacunar in 27 (24.6%) and of other type in 7 (6.4%). Ninety two patients (84.4%) had high blood pressure, 38% had high cholesterol levels, 35% had a cardiac disease and 26% were smokers. Thirty five subjects (31.8%) had a normal carotid ultrasonography, 46 (41.8%) had mural plaques, 16 (14.5%) had multiple plaques without occlusion, 13 (11.8%) had a partial occlusion and 7 (6.4%) had a total occlusion. Logistic regression analysis disclosed no significant relationship between stroke types and carotid atherosclerosis. Age was the only significant predictor for carotid atherosclerosis. CONCLUSIONS: The prevalence of severe carotid atherosclerosis in this group of stroke patients was less than expected.

Endoscopic laser surgery in the treatment of radiation failure of early laryngeal carcinoma.

BACKGROUND: This study was undertaken to analyze the local control rates and survival of patients undergoing endoscopic laser surgery for squamous cell carcinoma of the larynx as a salvage procedure for recurrent tumors after radiotherapy. METHODS: Twenty-four patients underwent endoscopic laser surgery for radiation failure at our hospital from 1988 to 1995. All patients were men, between 45 and 88 years old. The localization of the recurrence was in the supraglottis in 3 cases and in the glottis in 21 cases. The postirradiation recurrences were staged rT1 in 18 patients and rT2 in 6 patients. RESULTS: Local recurrence after laser surgery developed in six patients (25%) who had a total laryngectomy. Voice preservation was thus achieved in 75% of patients. No patient died because of the laryngeal cancer, and the observed 5-year survival rate was 76%. CONCLUSIONS: These results indicate that in selected cases, endoscopic laser surgery may be used successfully for treating radiation failure of early laryngeal carcinomas.

Effects of supplementation with folic acid and antioxidant vitamins on homocysteine levels and LDL oxidation in coronary patients.

Hyperhomocysteinemia is an important cardiovascular risk factor. Serum homocysteine levels are specially dependent on folate nutritional status. In addition, the oxidative modification of low-density lipoproteins (LDLs) in the endothelial microenvironment is a damaging factor that can be modified with fat-soluble antioxidant vitamins. The present study was done to assess the effect of a supplementation of folic acid and antioxidant vitamins on homocysteine levels and in vitro LDL oxidation in patients with coronary artery disease. Twenty-three patients with angiographically proven coronary artery disease were given supplements for 15 d consisting of one capsule twice a day of a multivitamin preparation containing 0.65 mg folic acid, 150 mg alpha-tocopherol, 150 mg ascorbic acid, 12.5 mg beta-carotene, and 0.4 microgram vitamin B12. Serum lipids, vitamin and homocysteine levels, and in vitro LDL oxidation were measured before and after the supplementation period. During the supplementation period, serum folate levels increased from 5.0 +/- 1.5 to 10.8 +/- 3.8 ng/mL (P < 0.001), vitamin B12 increased from 317.4 +/- 130.4 to 334.5 +/- 123.8 pg/mL (P < 0.05), and alpha-tocopherol increased from 8.2 +/- 5.1 to 13.7 +/- 7.9 mg/L (P < 0.001). Serum homocysteine levels decreased from 8.7 +/- 4.3 to 6.3 +/- 2.2 mumol/L (P < 0.001). In vitro LDL oxidation decreased from 2.6 +/- 1.1 to 1.6 +/- 1.1 nmol malondialdehyde/mg protein (P < 0.001). In comparing patients with healthy controls, basal levels of folate were lower in the patients, whereas vitamin B12, alpha-tocopherol, and homocysteine levels were similar. No changes in serum lipid levels or body weight were observed. In conclusion, a short-term supplementation with folic acid and antioxidant vitamins can reduce serum homocysteine levels and in vitro LDL oxidation in patients with coronary artery disease.

[Our experience with 1 mg BCG vaccine instillation in T1 stage cancer of the bladder]. / Nuestra experiencia con instilaciones de 1 mg de vacuna BCG en cáncer vesical etapa T1.

UNLABELLED: We studied 67 patients with bladder cancer in stage T1, with terminated BCG treatment and in pursuit. No stage Ta neither carcinoma in situ was included. The protocol was: beginning of treatment upon retiring vesical catheter, instilation of 1 mg of liofilized BCG vaccine (16 x 10(6) bacilles) in 40-50 ml of intravesical saline solution. A weekly instilation during the first month. An instilation each 15 days during the second and third month and one monthly until complete 12 months of treatment. Also was carried out an study of T lymphocites and cytokines. RESULTS: The average followup of the 67 patients treated was 51.3 months. 17 patients relapses (25.4%). A 33% were grade 3 and 27% grade 2. Like complications there was a case of inguinal TBC adenititis, 2 TBC prostatitis, 2 TBC cistitis and 5 cases of slight disuric syndrome. The study of subpopulations of lymphocites in peripheral blood demonstrated a significant increase of CD3 and CD4/CD8 ratio. The interleukin 2 measurement in serum also increased significantly after the BCG instilations. CONCLUSIONS: Our protocol gets similar results to the higher doses, but with minimal complications diminishing the relapses of the tumors in stage T1. A monthly maintenance dose would help to maintain immunity.

Morbilidad bucodental en niños de 5 a 9 años

Se realizó un estudio descriptivo-prospectivo en el Policlínico Docente de Area Sur de Placetas, en coordinación con la clínica dental de la propia área, a fin de determinar la morbilidad bucodental en niños entre 5 y 9 años de edad, durante 1997. Se utilizó la técnica de muestreo aleatorio estratificado y se estudiaron 545 niños a quienes se les aplicó un formulario que recogía datos de identidad personal, generales y hallazgos estomatológicos. El 100 por ciento de los niños examinados presentó al menos una afección bucodental; las caries ocupó el primer lugar, seguida por la maloclusión y la gingivitis. Se encontró relación de dependencia entre maloclusión y hábitos deformantes. La relación existente entre higiene bucodental deficiente, cepillado incorrecto e ingestión frecuente de confituras, sitúa a dichos factores como coadyuvantes en la génesis de la afecciones detectadas, lo que permite mejorar en la actualidad la labor educativa

Tuberculosis genitourinaria en la Araucania: experiencia en el Hospital Regional de Temuco / Genitourinary tuberculosis at Araucanía: experience at Hospital Regional de Temuco

Se estudian 62 casos con tuberculosis genitourinaria tratados entre 1989 y 1996. Corresponden a 41 hombres y 21 mujeres con un promedio de edad de 42,6 años. El 58,1 por ciento habita en localidad rural y un 37,1 por ciento tiene ascendencia mapuche. El 32,3 por ciento tiene antecedentes de tuberculosis anterior o concomitante. La latencia entre inicio de síntomas y diagnóstico fue de 13,1 meses, debutando el cuadro principalmente con hematuria macróscopica (45,2 por ciento), irritación vesical (44,9 por ciento) y dolor y/o aumento de volumen escrotal. La confirmación diagnóstica fue realizada en un 83,9 por ciento mediante cultivo y/o biopsia. Urocultivo de Koch fue positivo en un 69,4 por ciento. En el 90 por ciento la ecotomografía renal y un 74 por ciento la pielografía endovenosa resultaron alteradas, siendo el órgano más afectado el riñón. Fueron intervenidos quirúrgicamente 21 pacientes (33,9 por ciento). En 11 casos la evolución fue hacia una insuficiencia renal crónica. Todos recibieron tratamiento médico con esquema abreviado de 7 meses