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D M Nicholson

Publications and source records attributed to D M Nicholson.

11 recordsLinked to original sources
PubMed2002

An atomic force microscope-based investigation of vertical transport through GaAs/GaAlAs/InAlAs/GaAs step-barrier heterostructures.

Study of vertical transport through heterostructures consisting of single, double, or multiple quantum barriers is of both fundamental and technological interest. While extensive data regarding electron transport is available for single- and double-barrier structures, relatively less information is available for transport through step-barrier structures. In this paper, we present results from a study of room temperature vertical transport through a GaAs/GaAlAs/InAlAs/GaAs multistep-barrier heterostructure. A typical atomic force microscope has been adapted to perform transport measurements, thus allowing precise control of the physical location of the region of measurement. I-V measurements reveal negative differential resistance (NDR) peaks, thus confirming the formation of resonant states in a triangular well created when a voltage bias is applied across the step barrier. I-V curves have also been calculated by numerically solving the Schrödinger wave equation for this step-barrier structure. Comparison between the measured and calculated I-V curves shows reasonable agreement in the number of NDR peaks. However, discrepancies exist between the measured and calculated values for the voltages at which these NDR peaks occur. Some possible reasons for these discrepancies are discussed in this work.

Journal Article↗
PubMed1982

Cultured neurones from the mature bovine mediobasal hypothalamus contain LHRH but not catecholamine.

The in vitro culture of mature neurones from bovine mediobasal hypothalamus (MBH) is reported, providing a model for studies of mammalian neurosecretion at the cellular level. Explant tissue cultures of mature bovine MBH containing the arcuate nucleus were examined for LHRH, ACTH and catecholamines with a view to investigating the control of prolactin and gonadotropin secretion. LHRH immunoreactivity was found in both neuronal and non-neuronal cells in the outgrowth monolayer region of the explant. Neurones in this region appeared able to attach to a substrate and regenerate, in monolayer culture, well developed neurites characterized by beaded swellings as observed in vivo. Neither ACTH immunoreactivity nor catecholamine fluorescence was detected. Cultured neurones and astrocytes were labelled by tetanus toxin and anti-GFAP, respectively. Double labelling of cultures with tetanus toxin and anti-LHRH demonstrated the neuronal nature of many LHRH-immunoreactive cells. Radio-immunoassay data confirmed the presence of LHRH in the cultures but application of 60 mM KC1 failed to evoke hormone release. These studies have confirmed the view of previous workers that hypothalamic control of prolactin secretion in the bovine may be very different from that thought to occur in non-ruminants such as the rat and guinea pig. Finally, this work demonstrates that a cultured system from the mature bovine may prove a good model for study of neuronal regulation of gonadotropin secretion by the bovine mediobasal hypothalamus.

Adrenocorticotropic Hormone↗
PubMed1981

Polymicrobial purulent pericarditis.

A 63-year-old man had polymicrobial purulent pericarditis secondary to a silent esophageal perforation into the pericardium. His hospital course was complicated and prolonged. Defunctioning of his esophagus was needed to cure his pericarditis. The authors recommend an aggressive approach to his rare condition, emphasizing the importance of early defunctioning of the esophagus.

Bacterial Infections↗
PubMed1979

Traumatic abdominal hernia.

Traumatic abdominal hernias are rare, but are easily missed in patients with multiple injuries in whom life-threatening injuries take precedence. A case is reported in which difficulty was experienced with closure of the abdominal wall; at re-exploration a diagnosis of abdominal hernia was made, and a tear in the retroperitoneum with herniation of 2 feet of small bowel on the right side of the abdomen found. The hernia was reduced and the patient's recovery was uneventful. In all cases of celiotomy for trauma, complete exploration of the abdomen should be performed before closure to assure normal anatomic relationships of all structures.

Abdominal Injuries↗
PubMed1972

Mediastinoscopy.

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Adult↗