All-perylene-derivative for white light emitting diodes.

An organic-based bright white light emitting compound, namely Tb(H3PTC)3 [H4PTC = perylene-3,4,9,10-tetracarboxylic acid], able to be used as part of a white diode and as a part of a RGB system that can withstand high temperatures (∼700 K), is developed using perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and terbium(iii) nitrate pentahydrate as precursors by hydrothermal synthesis. Using PTCDA as the red emitter and the new derivative of it, Tb(H3PTC)3, as the blue-green emitter, along with a common deep blue LED can form a RGB system for display technologies, around room temperature. Temperature-dependent photoluminescence properties of the Tb(H3PTC)3 compound are also investigated for the involved excitonic-emission processes and the respective recombination lifetimes. The terbium(iii) complex was prepared using a procedure that is reproducible, easily modifiable, inexpensive, and environmentally friendly, opening new pathways for its large-scale applications. Unlike PTCDA, Tb(H3PTC)3 has been shown to be soluble in N-methyl-2-pyrrolidone (NMP) as well as in dilute aqueous solutions of this organic solvent in a straightforward procedure. The light emission properties are intimately correlated with the molecular structure and electronic properties of Tb(H3PTC)3 elucidated by experimental results of X-ray Absorption Near Edge Spectroscopy (XANES), Extended X-ray Absorption Fine Structure (EXAFS) and Density Functional Theory (DFT) calculations. A bright fluorescence yield is attained with a small amount of material either in solution or in solid form showing its potential to be used in state-of-the-art organic optoelectronic devices.

Ion-induced nanopatterns on semiconductor surfaces investigated by grazing incidence x-ray scattering techniques.

In this review we cover and describe the application of grazing incidence x-ray scattering techniques to study and characterize nanopattern formation on semiconductor surfaces by ion beam erosion under various conditions. It is demonstrated that x-rays under grazing incidence are especially well suited to characterize (sub)surface structures on the nanoscale with high spatial and statistical accuracy. The corresponding theory and data evaluation is described in the distorted wave Born approximation. Both ex situ and in situ studies are presented, performed with the use of a specially designed sputtering chamber which allows us to follow the temporal evolution of the nanostructure formation. Corresponding results show a general stabilization of the ordering wavelength and the extension of the ordering as a function of the ion energy and fluence as predicted by theory. The in situ measurements are especially suited to study the early stages of pattern formation, which in some cases reveal a transition from dot to ripple formation. For the case of medium energy ions crystalline ripples are formed buried under a semi-amorphous thick layer with a ripple structure at the surface being conformal with the crystalline/amorphous interface. Here, the x-ray techniques are especially advantageous since they are non-destructive and bulk-sensitive by their very nature. In addition, the GI x-ray techniques described in this review are a unique tool to study the evolving strain, a topic which remains to be explored both experimentally and theoretically.

Early stage of ripple formation on Ge(001) surfaces under near-normal ion beam sputtering.

We present a study of the early stage of ripple formation on Ge(001) surfaces irradiated by a 1 keV Xe(+) ion beam at room temperature and near-normal incidence. A combination of a grazing incidence x-ray scattering technique and atomic force microscopy allowed us to observe a variation of the symmetry of the surface nanopattern upon increase of the ion fluence. The isotropic dot pattern formed during the first minutes of sputtering evolves into an anisotropic ripple pattern for longer sputtering time. These results provide a new basis for further steps in the theoretical description of the morphology evolution during ion beam sputtering.

Dynamics of liquid 4He in vycor

Using inelastic neutron scattering, we have observed well-defined phonon-roton ( p-r) excitations in superfluid 4He in Vycor over a wide wave-vector range, 0.3

Phonons, rotons, and layer modes of liquid 4He in aerogel

We report the first observation of two-dimensional layer modes in both fully filled and partially filled aerogel. Using complementary high-energy resolution and high statistical precision neutron scattering instruments, and two different 87% porous aerogel samples, we show that the three-dimensional (3D) phonon-roton excitation energies and lifetimes of liquid 4He in aerogel are the same as in bulk 4He within current precision. The layer modes are the excitations that distinguish aerogel from the bulk rather than a difference in the 3D roton energy.

Nitrous oxide and day-case laparoscopy: effects on nausea, vomiting and return to normal activity.

Patients admitted for day-case laparoscopy were assigned randomly to receive nitrous oxide-oxygen or oxygen, with enflurane, during a standard anaesthetic technique. Postoperative morbidity, in particular nausea and vomiting, and ability to resume normal activity were assessed over the ensuing 48 h. Supplementary administration of propofol during the operative procedure was required significantly more often (P less than 0.05) in the absence of nitrous oxide. There was no significant difference in the incidence of vomiting before discharge when nitrous oxide was omitted. The incidence and severity of nausea over the 48 h following operation was similar in both groups. There was no difference in analgesic or anti-emetic requirements before discharge and the time taken to resume normal activity was similar. It is concluded that nitrous oxide may be avoided readily in day-case laparoscopy without affecting postoperative morbidity or time taken to return to "street fitness" and normal activity.

Post-operative morbidity associated with the use of atracurium and vecuronium in day-case laparoscopy.

Patients were randomly allocated to receive either vecuronium or atracurium as the sole muscle relaxant for day-case gynaecological laparoscopy to determine if either agent was superior with respect to post-operative morbidity during the 48 h after operation. Intubating conditions and cardiovascular stability were similar in both groups. Post-operative morbidity prior to discharge was also similar except for a significantly higher incidence of abdominal pain in the vecuronium group. There was no statistical difference in specific morbidity during the 48 h after laparoscopy, but a greater number of patients in the vecuronium group was able to resume normal activity 24 h after laparoscopy. Both agents are very suitable for day-case laparoscopies and other short surgical procedures.

Morbidity after day case laparoscopy. A comparison of two techniques of tracheal anaesthesia.

A comparison was made of postoperative morbidity following two anaesthetic techniques for day case laparoscopies. One group of patients was allowed to breathe spontaneously after intubation under suxamethonium. The second group received atracurium and their lungs were mechanically ventilated. Patients in the controlled ventilation group experienced significantly less severe sore throats and muscle pain in the first 24 hours postoperatively than the patients who breathed spontaneously. Both techniques proved to be safe and are suitable for day case laparoscopy. The safety of patients is discussed in relation to the choice of anaesthetic technique used.

Outpatient termination of pregnancy: halothane or alfentanil-supplemented anaesthesia.

Inhalation anaesthesia with halothane was compared with i.v. alfentanil in 66 unpremedicated patients undergoing suction termination of pregnancy as outpatients. Blood loss was significantly greater in the halothane group with a mean loss of 213 ml, compared with a mean loss of 89.8 ml in the alfentanil group. There was a greater frequency of nausea and vomiting in the alfentanil group, but no reduction in abdominal pain or need for analgesia after operation. Positive relationships were found between blood loss and duration of anaesthesia and between blood loss and gestational age in the halothane group, but not in the alfentanil group. We conclude that alfentanil-supplemented anaesthesia is satisfactory for suction termination of pregnancy when rapid recovery is required or the duration of the procedure is likely to be long, but that halothane anaesthesia cannot be recommended, especially if the procedure is long.

Anaesthesia for translumbar aortography.

Fifty patients presenting for elective translumbar aortography were randomly allocated to one of two groups receiving either enflurane or isoflurane. Premedication was with oral lorazepam. The patients' tracheas were intubated and they were allowed to breathe spontaneously in the prone position during the procedure. There was no significant difference in heart rate during the investigation but there was a statistically significant fall in the blood pressure from its pre-induction level. Arterial oxygenation was adequate throughout the procedure. Arterial carbon dioxide tension was significantly lower in the isoflurane group at the beginning and at end of the procedure (p less than 0.01), but there was no significant change in carbon dioxide tension within the groups during the procedure. Spontaneous ventilation with enflurane or isoflurane is a satisfactory anaesthetic technique for translumbar aortography.

Use of alfentanil in short anaesthetic procedures.

The pharmacokinetics of alfentanil, a new and very short-acting opioid, are discussed. Its use in day-case gynaecological procedures is described, and the results of the initial study presented. Alfentanil is a valuable adjunct to anaesthesia for day-case surgery and for short, painful procedures.

Double-blind crossover study of the efficacy and acceptability of oxazepam Expidet tablets compared to placebo in patients undergoing gynaecological surgery.

In a double-blind crossover trial, the hypnotic efficacy and acceptability of oxazepam Expidet, a fast-dissolving tablet, was compared to placebo in patients undergoing minor gynaecological surgery. Patients received 30 mg oxazepam Expidet or placebo the night before their operation and the alternate medication the night after. A sleep questionnaire was completed the morning after both nights and acceptability was assessed the morning after the second night. Data were available for analysis on seventy-two patients aged 18-50 years. There was a significant improvement in sleep onset and quality and less awakenings after oxazepam compared to placebo (p less than or equal to 0.01). There was no significant difference in the occurrence or type of dreams, or morning-after symptoms. There was a significant preference for oxazepam compared to placebo and for the fast-dissolving Expidet form compared to conventional tablets or capsules (p less than or equal to 0.01). There were no adverse reactions in the oxazepam group. It was concluded that oxazepam Expidet was an effective and acceptable hypnotic in this group of patients.

Cardiac arrhythmias during anaesthesia for laparoscopy.

Fifty-six patients undergoing elective laparoscopy were allocated randomly to two groups. Group H received alcuronium and were ventilated artificially using 0.5% halothane and nitrous oxide in oxygen. Group E breathed spontaneously a mixture of enflurane and nitrous oxide in oxygen. Arterial pressure, heart rate, tidal volume, respiratory rate and end-tidal carbon dioxide tension (PECO2) were monitored. The electrocardiogram (ECG) was recorded continuously using magnetic tape, from before induction until the patient left the recovery area. The incidence of arrhythmias was similar in the two groups. No arrhythmias occurred after the insufflated carbon dioxide had been removed from the abdomen. Spontaneous ventilation with enflurane anaesthesia is a simple and safe, technique for routine laparoscopy, providing the intra-abdominal pressure does not exceed 25 mm Hg.

Comparison of atracurium and alcuronium in day-case gynaecological surgery.

Alcuronium and atracurium were used on a randomised basis as part of the anaesthetic technique for out-patient gynaecological laparoscopy. Conditions for intubation and relaxation were similar but there was a marked decrease in the incidence of minor postoperative sequelae in the atracurium group.

Postoperative morbidity following gynaecological outpatient laparoscopy. A reappraisal of the service.

Fifty-six women having out-patient gynaecological laparoscopies were studied to determine anaesthetic problems and postoperative morbidity. It is concluded that the procedure is safe, and although the postoperative morbidity appears high it is very acceptable to the patient.

Anaesthesia for outpatient termination of pregnancy. A comparison of two anaesthetic techniques.

Inhalation anaesthesia with enflurane was compared with i.v. fentanyl for outpatient termination of pregnancy. Blood loss was greater in the enflurane group with a geometric mean loss of 73.0 ml compared with 43.9 ml in the fentanyl group. There was a greater frequency of nausea nd vomiting in the fentanyl group and no reduction in abdominal pain or need for analgesia after operation. A close relationship was found between blood loss and duration of the procedure but not between blood loss and gestational age or gestational age and anaesthetic time. Either technique is satisfactory for outpatient termination of pregnancy in unpremedicated patients. Despite the greater blood losses with enflurane, it is a safe and reliable method of anaesthesia for this procedure, but the concentration and duration of administration should be kept to a minimum.

Choice of ecbolic and the morbidity of day-case terminations of pregnancy.

In 103 women admitted for out-patient vaginal terminations of pregnancy, the relation was investigated between the use of ecbolics and blood loss, vomiting and other side effects. Patient self-rating was incorporated in the study for comparative purposes. Use of a combined preparation of oxytocin and ergometrine resulted in the lowest blood losses. Ergometrine administered alone was associated with immediate nausea and vomiting but no delayed effects. Seven days after abortion, 35% of the women were still complaining of vaginal bleeding, although in most the volume was low.

Morbidity after day-case gynaecological surgery. Comparison of enflurane with halothane.

In 105 patients undergoing day-case surgery recovery of consciousness was significantly faster after enfluane compared with halothane anaesthesia. There was no difference in postoperative morbidity between the two anaesthetic groups.

Morbidity in gynaecological day-case surgery. A comparison of two anaesthetic techniques.

The effectiveness of fentanyl, given as part of the anaesthetic technique, in reducing abdominal pain following outpatient gynaecological surgery has been examined. It was found to reduce significantly the frequency of abdominal pain in the period extending from discharge from hospital to the first evening, while not compromising surgical conditions nor increasing the frequency of other post-operative sequelae such as nausea and vomiting.