RESUMEN
It is demonstrated that valence-band mixing in GaAs quantum wells tremendously modifies electronic transport. A coherent control scheme in which ultrafast currents are optically injected into undoped GaAs quantum wells upon excitation with femtosecond laser pulses is employed. An oscillatory dependence of the injection current amplitude and direction on the excitation photon energy is observed. A microscopic theoretical analysis shows that this current reversal is caused by the coupling of the light- and heavy-hole bands and that the hole currents dominate the overall current response. These surprising consequences of band mixing illuminate fundamental physics as they are unique for experiments which are able to monitor electronic transport resulting from carriers with relatively large momenta.
RESUMEN
A further Swiss family with hereditary chronic relapsing pancreatitis is reported. Five members definitely have the disease, while in 4 subjects the condition is suspected. The five proven cases are a mother and her four children. All suffer from recurrent attacks of abdominal pain which started between the 8th and 20th year of life, and in all of them exocrine pancreatic insufficiency and pancreatic calcifications can be demonstrated. The mother has had diabetes mellitus since the age of 40 and 3 of the 4 children also have the disease, with age of onset between 15 and 29. In 3 patients insignificant traces of aminoacids could be detected in the urine. At 16 years one male patient had a pseudocyst of the pancreas surgically removed. All the others are treated conservatively. Reports on approximately 25 families with this disease have been published so far. The condition is inherited as an autosomal dominant disorder. Typically, the clinical symptoms begin during childhood or early adolescent life. The pathogenesis is unknown. It is possible that an abnormal pancreatic juice is produced which causes the intracanalicular calcifications. The treatment is identical to that in the non-hereditary forms, i.e. generally conservative. Recently some authors have favored a more aggressive approach consisting of pancreatico-jejunostomy or partial resection of the pancreas.
Asunto(s)
Pancreatitis/genética , Adolescente , Adulto , Anciano , Calcinosis/diagnóstico por imagen , Calcinosis/genética , Calcinosis/cirugía , Niño , Preescolar , Colangiografía/métodos , Enfermedad Crónica , Femenino , Humanos , Masculino , Pancreatitis/diagnóstico por imagen , Pancreatitis/cirugía , Linaje , Recurrencia , SuizaRESUMEN
The case is reported of a 39-year-old male with Steinert's dystrophia myotonica complicated by cardiac arrhythmias manifested by high-degree a-v block with Stokes-Adams attacks. Implantation of a demand-type cardiac pacemaker brought prompt relief from cardiac symptoms and the patient was able to resume work. The pathologico-anatomical findings in dystrophia myotonica are discussed, together with their possible connection with the type of arrhythmias described.
Asunto(s)
Síndrome de Adams-Stokes/terapia , Distrofia Miotónica/complicaciones , Marcapaso Artificial , Síndrome de Adams-Stokes/etiología , Adulto , Cardiomegalia/etiología , Humanos , MasculinoRESUMEN
Out of a total of 36,208 admissions during the 21-year period from 1954 to 1974, 514 female patients were hospitalized for acute myocardial infarction. Only 4 of these 514 females were below 40 years of age. In addition to one of the generally accepted risk factors for coronary disease, all 4 patients had been taking hormonal oral contraceptives for a prolonged period. Although there is no direct proof of a connection between the use of oral contraceptives and myocardial infarction, there is increasing evidence that risk factors for coronary disease are potentiated by the use of oral contraceptives. In the presence of risk factors for coronary disease, therefore, oral contraceptives should be taken only on the basis of a strict indication and under regular medical supervision.