Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 35
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
Science ; 369(6510): 1497-1500, 2020 09 18.
Artículo en Inglés | MEDLINE | ID: mdl-32943524

RESUMEN

Binary interactions dominate the evolution of massive stars, but their role is less clear for low- and intermediate-mass stars. The evolution of a spherical wind from an asymptotic giant branch (AGB) star into a nonspherical planetary nebula (PN) could be due to binary interactions. We observed a sample of AGB stars with the Atacama Large Millimeter/submillimeter Array (ALMA) and found that their winds exhibit distinct nonspherical geometries with morphological similarities to planetary nebulae (PNe). We infer that the same physics shapes both AGB winds and PNe; additionally, the morphology and AGB mass-loss rate are correlated. These characteristics can be explained by binary interaction. We propose an evolutionary scenario for AGB morphologies that is consistent with observed phenomena in AGB stars and PNe.

2.
Astrophys J ; 860(2)2018 Jun 18.
Artículo en Inglés | MEDLINE | ID: mdl-30185992

RESUMEN

Binarity is believed to dramatically affect the history and geometry of mass loss in AGB and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to search for hot binary companions to cool AGB stars using the GALEX archive, we discovered a late-M star, Y Gem, to be a source of strong and variable UV and X-ray emission. Here we report UV spectroscopic observations of Y Gem obtained with the Hubble Space Telescope that show strong flickering in the UV continuum on time-scales of ≲ 20 s, characteristic of an active accretion disk. Several UV lines with P-Cygni-type profiles from species such as Si IV and C IV are also observed, with emission and absorption features that are red- and blue-shifted by velocities of ~500 km s-1 from the systemic velocity. Our model for these (and previous) observations is that material from the primary star is gravitationally captured by a companion, producing a hot accretion disk. The latter powers a fast outflow that produces blue-shifted features due to absorption of UV continuum emited by the disk, whereas the red-shifted emission features arise in heated infalling material from the primary. The outflow velocities support a previous inference by Sahai et al. (2015) that Y Gem's companion is a low-mass main-sequence star. Blackbody fitting of the UV continuum implies an accretion luminosity of about 13 L⊙, and thus a mass-accretion rate > 5 × 10-7M⊙ yr-1; we infer that Roche lobe overflow is the most likely binary accretion mode for Y Gem.

3.
Astrophys J Lett ; 835(1)2017 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-28191303

RESUMEN

We have mapped 12CO J=3-2 and other molecular lines from the "water-fountain" bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with [Formula: see text] resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (> few × 106 cm-3), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to > 3.5 × 10-4M⊙ yr-1 in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, implies a substantial mass (0.017 M⊙) of very large (~mm-sized) grains. The measured expansion ages of the above structural components imply that the torus (age~160 yr) and the younger high-velocity outflow (age~110 yr) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi-Hoyle-Lyttleton wind accretion and wind Roche lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common envelope evolution are needed.

4.
Int J Surg Case Rep ; 7C: 124-6, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-25465646

RESUMEN

INTRODUCTION: Ileostomy is an iatrogenic entero-cutaneous (EC) fistula designed for controlled evacuation of bowel contents. Once ileostomy has served its purpose, it is reverted by surgical procedure. We are reporting an interesting case of spontaneous closure of an ileostomy, obviating the need of surgical intervention. PRESENTATION OF CASE: A 26 year old lady presented with perforation peritonitis. Upon exploration, a tubercular perforation of terminal ileum was found. Loop ileostomy was formed and patient was discharged on anti-tubercular treatment (ATT) after an uneventful recovery. During follow up visits, stoma was found to be retracting gradually. Retraction was not associated with any signs of peritonitis. Patient was able to pass stools per rectally. Stoma regressed completely within 8 months followed by epithelialisation of stoma site. Patient was leading an essentially normal life until her last follow up visit. DISCUSSION: Considering the various factors affecting spontaneous healing of EC fistulas, all the intestinal stomas do have favourable characteristics essential for spontaneous closure. However, this is seldom seen in day to day surgical practice. The factors pertaining to this particular case that led to spontaneous closure of stoma remain poorly understood. CONCLUSION: Further research is warranted to understand the mechanism behind spontaneous regression of a stoma. Relationship between this event and intestinal tuberculosis or ATT needs to be analysed.

5.
Int Immunopharmacol ; 5(6): 937-46, 2005 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-15829410

RESUMEN

In search of a potent immunomodulator to be used as an immunoprophylactic agent and as adjunct to chemotherapy against Leishmania infection, two analogs of muramyl dipeptide, viz. N.Ac-norMur-MeVal-D-isoGln (86/448) and N.AcMur-Acc-D-isoGln (89/729) were evaluated for desired activity. Effect of these peptides on cell mediated and humoral immunity was studied by immunizing the peptide treated mouse with sheep red blood cells (SRBC) and determining HA-titer, plaque forming cells assay and delayed type of hypersensitivity (DTH) response after 4-5 days. Both the peptides stimulated cell mediated immunity (CMI), humoral response as well as macrophage function in terms of super oxide anion (O2-) and nitric oxide (NO) generation. Mitogen induced lymphocyte proliferation and production of IL-2 and INF-gamma increased while that of IL-4 and IL-10 decreased by both the peptides showing a typical Th1 type response. After establishing the immunostimulatory activity, these peptides were evaluated for immunoprophylactic efficacy as well as for use as adjunct to chemotherapy with stibanate (SSG) against Leishmania donovani infection in golden hamster. These peptides were found quite effective in both the modes. In adjunct use the treatment may require lower dose of SSG and thereby reduce the chances of drug toxicity.


Asunto(s)
Acetilmuramil-Alanil-Isoglutamina/análogos & derivados , Acetilmuramil-Alanil-Isoglutamina/farmacología , Adyuvantes Inmunológicos/farmacología , Adyuvantes Inmunológicos/uso terapéutico , Leishmania donovani , Leishmaniasis Visceral/tratamiento farmacológico , Acetilmuramil-Alanil-Isoglutamina/uso terapéutico , Animales , Relación CD4-CD8 , Cricetinae , Citocinas/biosíntesis , Quimioterapia Combinada , Eritrocitos/inmunología , Leishmaniasis Visceral/parasitología , Leishmaniasis Visceral/prevención & control , Activación de Linfocitos , Macrófagos/efectos de los fármacos , Macrófagos/inmunología , Masculino , Ratones , Ratones Endogámicos BALB C , Óxido Nítrico/metabolismo , Ovinos/inmunología , Bazo/parasitología , Superóxidos/metabolismo
6.
Nature ; 426(6964): 261-4, 2003 Nov 20.
Artículo en Inglés | MEDLINE | ID: mdl-14628044

RESUMEN

Stars with masses in the range 1-8 solar masses (M(\circ)) live ordinary lives for approximately 10(9)-10(10) years, but die extraordinary deaths. First, during their death throes as asymptotic giant branch (AGB) stars they eject, over 10(4)-10(5) years, half or more of their mass in slowly expanding, spherical winds, and then, in a short (a few 100-1,000 years) and poorly understood phase, they are transformed into aspherical planetary nebula. Recent studies support the idea that high-speed, jet-like flows play a crucial role in this transformation. Evidence for such outflows is indirect, however; this phase is so short that few nearby stars are likely to be caught in the act. Here we report the discovery of a newly launched, high-speed jet-like outflow in the nearby AGB star, V Hydrae. We have detected both proper motions and ongoing evolution in the jet. These results support a model in which the jet is driven by an accretion disk around an unseen, compact companion. We also find a central, dense equatorial disk-like structure which may enable and/or enhance the formation of the accretion disk.

7.
J Forensic Sci ; 46(5): 1025-32, 2001 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-11569540

RESUMEN

A rapid, accurate, precise, reproducible, economical, and environmentally gentle method using capillary electrophoresis (CE) is presented for the routine analysis of methamphetamine, amphetamine, MDA, MDMA, MDEA, and cocaine in seized drugs. The methodology uses a 32 cm by 50 microm capillary (length to detector 23.5 cm) with a commercially available buffer kit and diode array UV detection. Dynamic coating of the capillary surface is accomplished by flushing with base for 1 min, a proprietary polycation for 1 min, and then a proprietary polyanion for 2 min. This approach provides a relatively high and stable electroosmotic flow (EOF), even at low pHs. The background electrolyte (BGE) contains 75 mM phosphate buffer (pH 2.5) with the same polyanion as above. Using this methodology, amphetamine, methamphetamine, MDA, MDMA, MDEA, and an internal standard (n-butylamphetamine) are baseline resolved in less than 5 min. The run-to-run migration time %RSDs and peak area %RSDs are typically <0.3% and <2.1%, respectively. The day-to-day and capillary-to-capillary migration time %RSDs are <1.5% and <2.1%, respectively. The %RSDs of the relative migration times compared with the internal standard on a day-to-day and capillary-to-capillary basis are <0.2% and <0.06%, respectively. The linear dynamic range using peak areas range from 0.003 to 0.10 mg/mL. The correlation coefficients are >0.9998, with all calibration curves passing at or near the origin. Similar data are obtained for cocaine and its internal standard henyltoloxamine. None of the compounds usually encountered in illicit samples interfere with the target compound (e.g., methamphetamine and cocaine) or the internal standard. Quantitative results for synthetic mixtures and seized exhibits are in good agreement with actual values, and also with results obtained from other techniques. The relatively high EOF for the dynamically coated capillary system allows for the screening of basic, acidic, and neutral adulterants in drug seizures; identification is facilitated by the use of automated UV library searches.

8.
Eur J Med Chem ; 36(5): 435-45, 2001 May.
Artículo en Inglés | MEDLINE | ID: mdl-11451532

RESUMEN

A number of 3-O-[2'-hydroxy-3'-N,N-aminopropan-1'-yl]-alpha-D-glucofuranoses were synthesised by regioselective oxirane ring opening in compound 2 with different secondary amines followed by selective deacetalisation. All the compounds were tested for their immunomodulatory potential in vitro; seven of them expressed significant immunostimulant activity.


Asunto(s)
Adyuvantes Inmunológicos/síntesis química , Adyuvantes Inmunológicos/farmacología , Disacáridos/síntesis química , Disacáridos/inmunología , Glucosa/análogos & derivados , Linfocitos/efectos de los fármacos , Adyuvantes Inmunológicos/química , Animales , Cromatografía en Capa Delgada , Disacáridos/química , Diseño de Fármacos , Glucosa/química , Activación de Linfocitos/efectos de los fármacos , Linfocitos/citología , Linfocitos/inmunología , Ratones , Espectroscopía Infrarroja Corta , Bazo , Relación Estructura-Actividad
9.
J Ethnopharmacol ; 71(1-2): 89-92, 2000 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-10904150

RESUMEN

Products of certain plants given to mothers after child birth or to invalids were studied for immunostimulant activity using the macrophage migration index (MMI) as a parameter of macrophage activation and cell-mediated immunity and haemagglutinating antibody (HA) titres and plaque-forming cell (PFC) counts as parameters of humoral immunity. Feeding of Prunus amygdalus (Almond(1)) and Buchanania lanzan (Chirronji(1)) significantly stimulated both CMI and humoral immunity in BALB/c mice as evidenced by the enhancement of MMI, HA titres, and PFC counts. Euryale ferox (Tel makhana(1)), Phoenix dactylifera (Chhohara(1)) and Zingiber officinale (Sonth(1)), however, stimulated humoral immunity to a greater extent than CMI. The observation provides scientific basis for feeding the products of above plants to mothers after child birth and to invalids with a relatively poor immune status.


Asunto(s)
Adyuvantes Inmunológicos/farmacología , Frutas/química , Medicina Ayurvédica , Plantas Medicinales/química , Animales , Inhibición de Migración Celular , Femenino , Hemaglutininas/análisis , Técnica de Placa Hemolítica , India , Trabajo de Parto , Masculino , Ratones , Ratones Endogámicos BALB C , Extractos Vegetales/química , Extractos Vegetales/farmacología , Embarazo
10.
Bioorg Med Chem Lett ; 10(11): 1181-3, 2000 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-10866376

RESUMEN

Twelve analogues of an immunomodulatory hexapeptide YVPGFP (I) derived from Proline rich peptide (from colostrum) have been synthesized with modifications at positions 2, 4 and 6. In MLR assay one of the analogues exhibited approx 50% inhibition at 0.1 microg/mL concentration in contrast to prednisolone and I which caused around 70 and 20% suppression respectively, at the same concentration.


Asunto(s)
Adyuvantes Inmunológicos/farmacología , Calostro/química , Oligopéptidos/farmacología , Péptidos/química , Secuencia de Aminoácidos , Animales , Activación de Linfocitos/efectos de los fármacos , Ratones , Oligopéptidos/química , Dominios Proteicos Ricos en Prolina
11.
Biochim Biophys Acta ; 1428(2-3): 433-45, 1999 Aug 05.
Artículo en Inglés | MEDLINE | ID: mdl-10434063

RESUMEN

A processed oligosaccharide mixture of buffalo milk induced significant stimulation of antibody, delayed-type hypersensitivity response to sheep red blood cells in BALB/c mice. This also stimulated non-specific immune response of the animals measured in terms of macrophage migration index. A novel pentasaccharide has been isolated from the oligosaccharide containing fraction having immunostimulant activity of buffalo milk. This compound was isolated by a combination of gel filtration chromatography, silica gel column chromatography of derivatised oligosaccharides while the homogeneity was confirmed by high performance liquid chromatography. The results of structural analyses, i.e. proton nuclear magnetic resonance, fast atom bombardment mass spectrometry, chemical transformations and degradations are consistent with the following structure: GlcNAcbeta(1-->3)Galbeta(1-->4)GlcNAcbeta(1-->3)Gal beta(1-->4)Glc


Asunto(s)
Adyuvantes Inmunológicos/química , Leche/química , Oligosacáridos/química , Adyuvantes Inmunológicos/aislamiento & purificación , Adyuvantes Inmunológicos/farmacología , Animales , Búfalos , Secuencia de Carbohidratos , Cromatografía en Gel , Cromatografía Líquida de Alta Presión , Sistema Inmunológico/efectos de los fármacos , Espectroscopía de Resonancia Magnética , Ratones , Ratones Endogámicos BALB C , Datos de Secuencia Molecular , Oligosacáridos/aislamiento & purificación , Oligosacáridos/farmacología , Espectrometría de Masa Bombardeada por Átomos Veloces
13.
Bioorg Med Chem Lett ; 8(4): 327-32, 1998 Feb 17.
Artículo en Inglés | MEDLINE | ID: mdl-9871679

RESUMEN

Human beta-casein fragment (54-59) having the amino acid sequence Val-Glu-Pro-Ile-Pro-Tyr, has been shown potent immunostimulant activity. Several analogs of this hexapeptide have been synthesized with modification in the N-terminal region and tested for their immunomodulatory activity. Interestingly, two hexapeptides have shown significant immunosuppressant activity.


Asunto(s)
Caseínas/química , Inmunosupresores/farmacología , Fragmentos de Péptidos/farmacología , Secuencia de Aminoácidos , Animales , Células Cultivadas , Humanos , Activación de Linfocitos/efectos de los fármacos , Prueba de Cultivo Mixto de Linfocitos , Ratones , Fragmentos de Péptidos/química
14.
J Ethnopharmacol ; 56(3): 233-6, 1997 May.
Artículo en Inglés | MEDLINE | ID: mdl-9201614

RESUMEN

Pippali Rasayana (PR), an Indian ayurvedic drug prepared from Palash (Butea monosperma (Lamk) Kuntze; Leguminaceae) and Pippali (Piper longum L.; Piperaceae), was administered at a dose of 1 g p.o. three times daily for a period of 15 days to patients (25 treated, 25 placebo controls) suffering from giardiasis with clinical signs and symptoms, and stools positive for trophozoites/cysts of Giardia lamblia. After 15 days of drug treatment there was a complete disappearance of G. lamblia (trophozoites/cysts) from the stools of 23 out of 25 patients. General signs and symptoms of ill health and abdominal discomfort, presence of mucus, pus cells and RBCs were significantly reduced. There was a marked improvement in the clinical and haematological profile of the patients. Spontaneous recovery in 20% cases was recorded in placebo controls.


Asunto(s)
Giardiasis/tratamiento farmacológico , Extractos Vegetales/uso terapéutico , Adyuvantes Inmunológicos/uso terapéutico , Antiprotozoarios/uso terapéutico , Método Doble Ciego , Heces/parasitología , Giardiasis/inmunología , Giardiasis/parasitología , Humanos , India , Medicina Ayurvédica
15.
Immunopharmacol Immunotoxicol ; 18(4): 511-28, 1996 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-8933167

RESUMEN

Structural analogs of the hexapeptide sequence 54-59 (A) human casein, reported to stimulate immune response, were synthesized and evaluated for immunostimulant activity. Hexapeptide 91/409 (C), 90/649 (D) and 91/361 (E) stimulated higher antibody titre and delayed type of hyper-sensitivity (DTH) response than the natural casein hexapeptide in BALB/c mice-sheep red blood cells (SRBC) and guinea pig-ovalbumin models. These peptides also induced higher stimulation of non-specific immune response as evidenced by increase in macrophage migration index (MMI), phagocytosis of (14C) lecuine labelled Escherchia coli, incorporation of (14C)-glucosamine in peritoneal macrophages and proliferative response of mouse thymocytes. Significant suppression on the course of Plasmodium berghei infection was also observed on day 4, in the animals treated with hexapeptidse C and D.


Asunto(s)
Adyuvantes Inmunológicos/biosíntesis , Adyuvantes Inmunológicos/farmacología , Caseínas/inmunología , Caseínas/farmacología , Fragmentos de Péptidos/biosíntesis , Fragmentos de Péptidos/inmunología , Animales , Formación de Anticuerpos/efectos de los fármacos , Especificidad de Anticuerpos/efectos de los fármacos , Caseínas/biosíntesis , Eritrocitos/inmunología , Femenino , Cobayas , Humanos , Hipersensibilidad Tardía/inmunología , Ratones , Ratones Endogámicos BALB C , Ovalbúmina/inmunología
16.
Indian J Ophthalmol ; 43(2): 73-4, 1995 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-8818314

RESUMEN

To evaluate the effects of topical timolol on lipid profile, blood samples from 25 patients (16 males and 9 females) were analysed before topical instillation of 0.5% timolol maleate and thereafter at one month and two months. After two months of therapy, the level of high density lipoprotein (HDL) decreased significantly (p < 0.02). The levels of low density lipoprotein (LDL), very low density lipoprotein (VLDL) and triglyceride increased but the changes were not statistically significant. Since low level of HDL is strongly associated with increased risk of myocardial infarction, our study cautions use of topical timolol in patients with low levels of HDL or with previous history of coronary heart disease.


Asunto(s)
Antagonistas Adrenérgicos beta/farmacología , Lípidos/sangre , Timolol/farmacología , Administración Tópica , Antagonistas Adrenérgicos beta/administración & dosificación , Adulto , HDL-Colesterol/sangre , LDL-Colesterol/sangre , VLDL-Colesterol/sangre , Femenino , Humanos , Masculino , Persona de Mediana Edad , Soluciones Oftálmicas , Timolol/administración & dosificación , Triglicéridos/sangre
17.
Astrophys J ; 394(1 Pt 1): 320-39, 1992 Jul 20.
Artículo en Inglés | MEDLINE | ID: mdl-11540051

RESUMEN

We have made a search for SO in the mass-loss envelopes of 24 mostly oxygen-rich red giants, using the 8(8)-7(7) (344.3 GHz), 6(5)-5(4) (219.9 GHz), 4(3)-3(2) (138.2 GHz), and 3(2)-2(1) (99.3 GHz) transitions. One or more of these transitions were detected toward 14 envelopes, including those of the supergiants VY CMa and IRC +10420. The SO envelope of IK Tau was measurably extended, and that of IRC +10420 marginally so, allowing us to determine the envelope sizes directly. The SiO (v = 0) J = 8-7, J = 5-4, and J = 3-2 lines at 347.3, 217.1, and 130.3 GHz were detected simultaneously with the 344.3, 219.9, and 138.2 GHz SO lines, respectively. From our SO data, as well as from SO2 data published elsewhere (for a few sources), we derive the circumstellar SO and SO2 abundances and compare them with theoretical predictions. We find that the photospheric abundances of SO and SO2 are insignificant, and that SO and SO2 must be produced in the circumstellar envelopes. However, the (average) SO abundances are larger than even the peak values predicted by nonequilibrium circumstellar chemistry models. The large SO abundances imply that S is not heavily depleted into grains in these envelopes, and further suggest that (i) the stellar mass-loss rates in these objects are substantially larger than accepted values, (ii) the circumstellar H/H2 abundance ratio is quite small, and (iii) the reaction of O and SH dominates over the reaction of S and OH in the production of SO. In the peculiar bipolar nebula OH 231.8+4.2, the combined SO and SO2 abundance exceeds the cosmic S abundance, if the mass-loss rate in this object is smaller than or equal to l0(-4) M solar yr-1. In IK Tau the data can only be fitted with models in which the SO is distributed in a hollow shell, as predicted by the nonequilibrium chemistry models. In another three, which have no measurable OH, the discovery of SO is difficult to explain by such models.


Asunto(s)
Medio Ambiente Extraterrestre , Modelos Químicos , Dióxido de Azufre/análisis , Óxidos de Azufre/análisis , Fenómenos Astronómicos , Astronomía , Polvo Cósmico , Gases/análisis , Hidrógeno/análisis , Oxígeno/análisis , Análisis Espectral
18.
Proc Natl Acad Sci U S A ; 85(20): 7782-5, 1988 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-3174662

RESUMEN

Single amino acid substitutions at the rim of the receptor binding site of the hemagglutinin molecule of swine influenza virus markedly influence the replicative capacity of the virus in chicken embryos, Madin-Darby canine kidney cells (MDCK), and swine as well as its antigenic phenotype. Mutants of low-yield (L) phenotype replicate poorly in chicken embryos and produce small plaques in MDCK cells but are highly infective for swine. Such mutants have lysine at position 153 and glycine at position 155 of the hemagglutinin (residues 156 and 158 in the H3 model). High-yield (H) mutants have the converse replicative characteristics and can be antigenically distinguished from L mutants (and from each other) based on their differential reactivity with two monoclonal antibodies, 9C8 and Sa-13. H mutants differ from L mutants in that the H mutants express glutamic acid at either position 153 or 155. L and H mutants act in an allelic fashion in effecting predictable one-step adaptation to different hosts. Selection for replication (e.g., high-yielding) phenotype results in concordant pleiotropic change in antigenic phenotype and in genotype. Conversely, immunoselection leads to change in replicative phenotype. Although the mechanism by which these mutations affect viral replication has not yet been defined, they may reflect differences in the affinity of each mutant for different host receptors.


Asunto(s)
Hemaglutininas Virales/genética , Virus de la Influenza A/genética , Polimorfismo Genético , Animales , Línea Celular , Embrión de Pollo , Virus de la Influenza A/crecimiento & desarrollo , Virus de la Influenza A/fisiología , Mutación , Fenotipo , Porcinos , Replicación Viral
19.
Appl Opt ; 27(21): 4554-61, 1988 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-20539607

RESUMEN

We examine theoretically and experimentally the properties of two electrooptic devices based on quantum confined Stark effect of excitonic transitions. These two devices are shown to be critical in implementation of the Hopfield model as well as other neural type networks for associative memories. P-i(multiquantum wells)-n structures using GaAs/AlGaAs provide a controller-modulator device which has integrating-thresholding properties required of neurons. The p-i-n structures also provide programmable modulators which can serve as a synaptic mask. Using Monte Carlo techniques we examine an all-optical architecture to implement the Hopfield network. No external feedback-thresholding circuitry is required in this implementation due to special design of the controller-modulator device. Speed and stability issues of this architecture are also addressed. The computer simulation results provide valuable insight into how the controllermodulator device should be improved for better network implementation.

20.
Br J Urol ; 59(3): 261-3, 1987 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-3567489

RESUMEN

A new technique for the repair of a urethral fistula at the penoscrotal junction is presented. Under local anaesthesia we have successfully repaired six of these fistulae using a groin island pedicle flap. The urethra is repaired by mobilising the mucous lining around the fistula and closing it longitudinally, using absorbable 4/0 chromic catgut sutures. The groin island pedicle flap which is based on superficial circumflex iliac vessels is used to cover the repaired lining. The donor defect is closed primarily. In all six cases there was primary healing. This procedure is recommended for cases where the skin around the fistula is badly scarred or where previous attempts at closure have failed. Moderate defects of penile and scrotal skin can also be repaired by this type of flap.


Asunto(s)
Colgajos Quirúrgicos , Enfermedades Uretrales/cirugía , Fístula Urinaria/cirugía , Humanos , Masculino , Métodos
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA