Discovery and insights from DSX mission's high-power VLF wave transmission experiments in the radiation belts.

Space weather phenomena can threaten space technologies. A hazard among these is the population of relativistic electrons in the Van Allen radiation belts. To reduce the threat, artificial processes can be introduced by transmitting very-low-frequency (VLF) waves into the belts. The resulting wave-particle interactions may deplete these harmful electrons. However, when transmitting VLF waves in space plasma, the antenna, plasma, and waves interact in a manner that is not well-understood. We conducted a series of VLF transmission experiments in the radiation belts and measured the power and radiation impedance under various frequencies and conditions. The results demonstrate the critical role played by the plasma-antenna-wave interaction around high-voltage space antennae and open the possibility to transmit high power in space. The physical insight obtained in this study can provide guidance to future high-power space-borne VLF transmitter developments, laboratory whistler-mode wave injection experiments, and the interpretation of various astrophysical and optical phenomena.

Growth inhibition of psoriatic keratinocytes by quinazoline tyrosine kinase inhibitors.

Psoriasis is characterized by hyperproliferation of keratinocytes associated with an inflammatory infiltrate in the epidermis. Among factors which may be related to hyperplasia of psoriatic keratinocytes is the persistent autocrine stimulation of the epidermal growth factor receptor (EGFR) by transforming growth factor-alpha. Owing to the pivotal role of the EGFR in driving the growth of human psoriatic keratinocytes, we examined two selective inhibitors of EGFR kinase activity: 4-(3-bromophenylamino)-6, 7-dimethoxyquinazoline (AG1517/SU5271) and 4-(3-chlorophenylamino)-6, 7-dimethoxyquinazoline (AG1478) on psoriatic keratinocytes. SU5271 potently inhibits ligand-induced autophosphorylation of EGFR, and downstream signal transduction events, including DNA replication and cell cycle progression. SU5271, at micromolar concentrations, inhibited the proliferation of keratinocytes isolated from psoriatic lesions in excellent correlation with its EGFR kinase inhibitory activity in these cells. Biologically active concentrations of SU5271 penetrated human cadaver skin, suggesting that this compound is a strong candidate as an antipsoriatic agent.

Looking for the artery of Adamkiewicz: a quest to minimize paraplegia after operations for aneurysms of the descending thoracic and thoracoabdominal aorta.

All patients undergoing resection of thoracic or thoracoabdominal aneurysms at Mount Sinai Hospital since November 1993 had spinal cord function monitored with somatosensory-evoked potentials as part of a multimodality approach to reducing spinal cord injury. In the segment to be resected, each pair of intersegmental vessels was sequentially clamped, and they were subsequently sacrificed only if no change in somatosensory evoked potentials occurred within 8 to 10 minutes after occlusion. Adjunctive protective measures included mild hypothermia (31 degrees to 33 degrees C), distal perfusion, corticosteroids, maintenance of high normal blood pressures, avoidance of nitroprusside, and cerebrospinal fluid drainage. Ninety-five consecutive patients operated on since 1993 (group II) were compared with 138 earlier patients (group I). Preoperative characteristics such as age, sex, etiology of aneurysm, emergency operation, and reoperation did not differ between groups, nor did operative variables such as incidence of rupture and extent of resection. Group I had slightly more smokers and slightly fewer hypertensive individuals. Group II patients had a significantly better outcome with respect to in-hospital mortality (10.5% vs 18%, p = 0.045) and paraplegia (2% vs 8%, p = 0.008). By multivariate analysis, rupture and diabetes were associated with significantly higher in-hospital mortality, and smoking greatly increased the incidence of paraplegia. The extent of the aneurysm was a major determinant of mortality and paraplegia. The low paraplegia rate in group II was achieved without reattachment of a single intercostal or lumbar artery. No patient with fewer than 10 intersegmental arteries severed had paraplegia, and spinal cord ischemia was reversible in three patients after adjunctive maneuvers were performed to improve perfusion, suggesting that spinal cord blood supply is unlikely to depend on a single "artery of Adamkiewicz."