Temperature and flow modulation doping of manganese in ZnS electroluminescent films by low pressure metalorganic chemical vapor deposition

A temperature and flow modulation (TFM) technique has been developed to modulate the manganese doping profile in ZnS phosphor material grown by lowpressure metalorganic chemical vapor deposition for alternating-current thin film electroluminescent devices (TFELDs). In the TFM technique, modulation of both the substrate temperature as well as the flows of metalorganic sources, diethylzinc and tricarbonyl-(methylcyclopentadienyl)-manganese (TCPMn), was used to grow a structure consisting of alternating layers of undoped ZnS at 400°C and Mn-doped ZnS where Mn being incorporated into the undoped ZnS at 550°C. X-ray results indicated that MnS_x phases were present within the ZnS host crystal matrix for the modulation doped samples, while a Mn_xZn_1-xS solid solution was present in the uniformly doped samples. The luminescence efficiency of the TFELDs could be modified by growing the phosphor with dopant (luminescent center) modulation. The TFELDs with a single modulated doping phosphor layer showed lower threshold voltages in the range 70 to 80 V with light emission in the 580 to 587 nm wavelength range. With a twofold increase in the total thickness of the undoped ZnS layer, the brightness and the luminescence efficiency, measured at the threshold voltage plus 40 V, increased by a factor of 20 and 10, respectively. The electroluminescent (EL) characteristics of the phosphors with multiple dopant layers showed higher luminescence efficiency. By using the TFM growth technique, one can engineer the luminescent center distribution in the phosphor layer to improve the EL characteristics.     

American monitoring: standard and state of the art

Monitoring of the anesthetized patient, the anesthesia machine, and the patient-machine interface is an essential component of anesthetic practice in order to prevent anesthetic-related injuries resulting from equipment failure or human error. While the optimal monitor to detect anesthetic problems (hypoxia, esophageal intubation, hemodynamic compromise, for example) is unclear at present, American standards require continuous presence of qualified personnel who evaluate patient oxygenation, ventilation, circulation, and temperature. A common monitoring array includes electrocardiogram, autosphygmomanometer, pulse plethysmography/oximetry, stethoscope, anesthetic gas analyzer, thermistor, and nerve stimulator. The role of emerging technologies, including transesophageal echocardiography, automated electrocardiographic analysis of ST segments, transcranial Doppler, and transcranial near infrared spectroscopy are discussed.     

Muscle sympathetic nerve activity is reduced in IDDM before overt autonomic neuropathy

Studies of heart-rate variability have demonstrated that abnormal cardiac parasympathetic activity in individuals with IDDM precedes the development of other signs or symptoms of diabetic autonomic neuropathy. To determine whether IDDM patients have impaired sympathetic activity compared with normal control subjects before the onset of overt neuropathy, we directly recorded MSNA. We also examined the effects of changes in plasma glucose and insulin on sympathetic function in each group. MSNA was recorded by using microneurographic techniques in 10 IDDM patients without clinically evident diabetic complications and 10 control subjects. MSNA was compared during a 15-min fasting baseline period and during insulin infusion (120 mU.m-2.min-1) with 30 min of euglycemia. A cold pressor test was performed at the end of euglycemia. Power spectral analysis of 24-h RR variability was used to assess cardiac autonomic function. IDDM patients had lower MSNA than control subjects at baseline (8 +/- 1 vs. 18 +/- 3 burst/min, P < 0.02). MSNA increased in both groups with insulin infusion (P < 0.01) but remained lower in IDDM patients (20 +/- 3 vs. 28 +/- 3 burst/min, P < 0.01). In the IDDM group, we found no relationships between MSNA and plasma glucose, insulin, or HbA1c concentrations. BP levels did not differ at rest or during insulin. Heart-rate variability and the MSNA response to cold pressor testing in IDDM patients did not differ from those in healthy control subjects. IDDM patients had reduced MSNA at rest and in response to insulin. The lower MSNA is not attributable to differences in plasma glucose or insulin, but, rather, is most likely an early manifestation of diabetic autonomic neuropathy that precedes impaired cardiac parasympathetic control.     

d-step lattice-ladder predictor in terms of one-step lattice-ladder predictors

In this note, it is shown that ad-step lattice-ladder predictor may be expressed in terms of one-step lattice-ladder predictors.     

Oxidation-reduction behaviour of La-doped SrTiO3

Thermogravimetric measurements as a function of oxygen activity were performed in the temperature range of 1200 to 1400° C on a series of lanthanum SrTiO₃ compounds. A model which assumes the absorption of excess oxygen in the structure which compensates the donors by formation of cationic defects is postulated. Comparison of this model with the experimental results show reasonable agreement.On leave from the Faculty of Engineering, Cairo University, Egypt.     

Clinical features and MR imaging in children with repaired myelomeningocele

The aim of the study is to define the role of associated malformations in the clinical evolution of children affected by myelomeningocele. MRI investigation of the spinal cord was carried out on 25 patients between the age of 7.3 and 18.10 with MMC repaired and followed up for at least 7 years. The relation between associated malformations demonstrated by MRI and clinical trend was analysed. The results are the following: 1) presence of asymptomatic tethered cord in all cases; 2) high frequency (92%) of Chiari malformation; 3) presence of syringomyelia in 20% of patients, symptomatic in 1; 4) presence of ventricular enlargement in 72% of cases without increased intracranial pressure syndrome. For a better therapeutic approach prospective MRI studies are needed in order to follow up associated malformations.