Population inversion in a single InGaAs quantum dot using the method of adiabatic rapid passage.

Preparation of a specific quantum state is a required step for a variety of proposed quantum applications. We report an experimental demonstration of optical quantum state inversion in a single semiconductor quantum dot using adiabatic rapid passage. This method is insensitive to variation in the optical coupling in contrast with earlier work based on Rabi oscillations. We show that when the pulse power exceeds a threshold for inversion, the final state is independent of power. This provides a new tool for preparing quantum states in semiconductor dots and has a wide range of potential uses.

Cryogenic confocal microscopy with rotation in a magnetic field.

Two approaches to conducting magneto-optical confocal spectroscopy are described, in each of which the confocal head is rotatable with respect to the magnetic field. A coudé arrangement has been shown to give adequate performance for scanned imaging, but lower optical throughput than a system based on single-mode optical fiber transport. The design criteria for a cryogenic fiber-coupling objective are described, and the tolerances demanded in lens alignment are shown to be relatively benign, allowing manufacture without special techniques. The practical use of the rotating confocal system with commercial stick-slip positioners has been shown to be rigid enough, and asymmetric weight distribution and diamagnetic forces are small enough to permit single quantum emitters to be studied over a range of angles and field strengths.

Moving nanoparticles with Raman scattering.

We show how to change optically the distance between two protein-linked gold nanoparticles by Raman-induced motion of the linker protein. Rayleigh scattering spectroscopy of the coupled-particle plasmon allows us to compare the inter-nanoparticle distance of individual protein-linked gold nanoparticle dimers before and after surface-enhanced Raman scattering (SERS). We find that low-intensity (50 microW/microm2) laser light in resonance with the nanoparticle-dimer plasmon provokes a change of the inter-nanoparticle distance on the order of 0.5 nm whenever SERS from the proteins connecting the nanoparticles can be observed.

Influence of copolymer interface orientation on the optical emission of polymeric semiconductor heterojunctions.

We have examined the Coulombic interactions at the interface in a blend of two copolymers with intramolecular charge-transfer character and optimized band offsets for photoinduced charge generation. The combination of both time-resolved measurements of photoluminescence, and quantum-chemical modeling of the heterojunction allows us to show that relative orientation across the heterojunction can lead to either a repulsive barrier ( approximately 65 meV) or an attractive interaction which can enhance the charge-transfer processes. We conclude that polymer orientation at the heterojunction can be as important as energy-band offsets in determining the dynamics of charge separation and optical emission.

Excitation migration along oligophenylenevinylene-based chiral stacks: delocalization effects on transport dynamics.

Atomistic models based on quantum-chemical calculations are combined with time-resolved spectroscopic investigations to explore the migration of electronic excitations along oligophenylenevinylene-based chiral stacks. It is found that the usual Pauli master equation (PME) approach relying on uncoherent transport between individual chromophores underestimates the excitation diffusion dynamics, monitored here by the time decay of the transient polarization anisotropy. A better agreement to experiment is achieved when accounting for excitation delocalization among acceptor molecules, as implemented in a modified version of the PME model. The same models are applied to study light harvesting and trapping in guest-host systems built from oligomers of different lengths.

Coherent control of optical emission from a conjugated polymer.

We have observed that resonant Rayleigh scattering dominates the emission from poly(p-phenylene vinylene) excited with photons at energies below the threshold at which excitonic migration is reduced. The intensity of the resonant emission decays exponentially with a lifetime of up to 450 fs after pulsed excitation. The coherent nature of the emission was confirmed by angular variations in the far-field emission intensity-bright and dark speckles. Persistence of a coherent polarization was demonstrated by coherent control using phase-locked pulses.

One year's trauma mortality experience at Brooke Army Medical Center: is aeromedical transportation of trauma patients necessary?

The purpose of this study was to review whether air ambulance transportation of trauma patients to the Brooke Army Medical Center (BAMC) level I trauma center contributed to maintaining national mortality standards in the trauma care of these patients. Aeromedical transportation is considered a standard-of-care component of regional trauma systems throughout the United States. Pooled trauma database information from 792 consecutive ambulance-transported trauma patients received at BAMC during the fiscal year from October 1, 1995, to September 30, 1996, were reviewed. The 792 trauma patients were composed of 687 patients transported by ground ambulance and 105 patients who received helicopter aeromedical evacuation. Aeromedical evacuation was associated with increased levels of prehospital medical care and faster transportation than ground ambulance service. The mortality rates (immediate, early, and late deaths) of both ambulance groups were compared with national mortality standards using the internationally recognized Trauma and Injury Severity Score methodology, based on the Major Trauma Outcome Study in 1986 and validated in 1992. The Z test for independent populations demonstrated no statistically significant difference between BAMC trauma mortality rates for either ambulance group compared with national trauma mortality rates. The results suggest that aeromedical evacuation of the more severely injured patients farthest from the BAMC trauma center resulted in mortality rates that met national standards.

Comparative efficacy of nifedipine gastrointestinal therapeutic system versus diltiazem when added to beta blockers in stable angina pectoris.

To determine the relative efficacy of nifedipine gastrointestinal therapeutic system (GITS) and diltiazem, 20 patients with angina pectoris and coronary artery disease were studied in a double-blinded, placebo-controlled randomized crossover trial. All patients were taking concomitant beta blockers. Efficacy was assessed by symptoms, exercise treadmill testing, and ambulatory ST-segment monitoring at baseline and after 6 weeks on each medication. Mean daily dose was titrated to 119 +/- 7 mg (nifedipine GITS) and 342 +/- 59 mg (diltiazem). The addition of either nifedipine GITS or diltiazem resulted in a significant reduction in angina frequency, improvement in exercise treadmill duration (7 vs 7 and 8 minutes; baseline vs nifedipine GITS and diltiazem), time to angina onset (4 vs 7 and 7 minutes; baseline vs nifedipine GITS and diltiazem), and time to ST-segment depression (5 vs 6 and 7 minutes; baseline vs nifedipine GITS and diltiazem). There was no significant difference between nifedipine GITS and diltiazem with respect to the magnitude of improvement in anginal symptoms or exercise test parameters. Both nifedipine GITS and diltiazem reduced the overall frequency and duration of ischemic episodes on ambulatory monitoring, but this reduction was not statistically different. Thus, nifedipine GITS and diltiazem at maximally tolerated doses were equally effective at reducing angina and increasing exercise tolerance as beta blockers alone.

Prosecuting assaultive psychiatric patients.

For many reasons, inpatient psychiatric units are increasingly faced with treatment and management of violent individuals. This fosters a need to consider potential institutional responses to patient violence. This paper focuses on one response--prosecution of these persons. The existing literature on this topic is reviewed. In addition, the case history of a difficult but successful prosecution of an assaultive patient is presented. This case highlighted the development of guidelines, which are outlined herein, for determining the appropriateness of seeking legal action against patients. The paper concludes with an assessment of the benefits and risks associated with patient prosecution.

Effect of nifedipine on total ischemic activity and circadian distribution of myocardial ischemic episodes in angina pectoris.

A randomized, double-blind, crossover study was conducted in 10 patients to assess the effect of nifedipine versus placebo on total ischemic activity and circadian distribution of ischemic episodes. After baseline exercise treadmill testing and 48-hour ambulatory electrocardiographic ST-segment monitoring, patients received either nifedipine (mean dose, 80 mg/day) or placebo administered 4 times per day, with the initial dose taken immediately upon arising in the morning. Patients were maintained on a stable dose of each study drug for 7 days, after which they underwent repeat exercise treadmill testing and 48-hour ambulatory electrocardiography. During exercise treadmill testing, greater exercise duration was achieved by patients receiving nifedipine than by those receiving placebo (421 +/- 121 vs 353 +/- 155 seconds, respectively; p less than 0.05). Time to greater than or equal to 1 mm ST depression was significantly greater with nifedipine (282 +/- 146 seconds) than at baseline (130 +/- 72 seconds, p less than 0.003) and with placebo (150 +/- 98 seconds, p less than 0.0005). During ambulatory electrocardiographic monitoring, nifedipine reduced both the total number of ischemic episodes (18 vs 54 at baseline and 63 with placebo; p less than 0.02 for both) and the total duration of ischemia (260 vs 874 at baseline and 927 minutes with placebo; p less than 0.02 for both). The surge of ischemia between 06:00 and 12:00 noted at baseline and during placebo therapy was nearly abolished during nifedipine treatment. Nifedipine at this dosage, administered in this manner, is effective in reducing total ischemic activity and may prevent morning surges of ischemic episodes.

Angina and exertional myocardial ischemia in diabetic and nondiabetic patients: assessment by exercise thallium scintigraphy.

Patients with diabetes mellitus and coronary artery disease are thought to have painless myocardial ischemia more often than patients without diabetes. We studied 50 consecutive patients with diabetes and 50 consecutive patients without diabetes, all with ischemia, on exercise thallium scintigraphy to show the reliability of angina as a marker for exertional ischemia. The two groups had similar clinical characteristics, treadmill test results, and extent of infarction and ischemia, but only 14 [corrected] patients with diabetes compared with 34 [corrected] patients without diabetes had angina during exertional ischemia. In diabetic patients the extent of retinopathy, nephropathy, or peripheral neuropathy was similar in patients with and without angina. Angina is an unreliable index of myocardial ischemia in diabetic patients with coronary artery disease. Given the increased cardiac morbidity and mortality in such patients, periodic objective assessments of the extent of ischemia are warranted.

Silent myocardial ischemia: clinical characteristics, underlying mechanisms, and implications for treatment.

A great deal of interest is being generated by the possibility that patients with coronary artery disease and typical angina pectoris may also experience periods of ischemia during activities of daily living that are not necessarily associated with angina or increased myocardial oxygen demand. It might be that the majority of ischemic episodes during daily life are not preceded by increases in myocardial oxygen demand, and are probably related to dynamic changes in coronary blood flow. Questions still remain, however, regarding the prevalence of asymptomatic ischemia in patients who present with effort angina and positive results on exercise tolerance tests. Therefore, in susceptible patients with coronary artery disease, calcium channel blockers, especially nifedipine, may be of particular benefit since they decrease myocardial oxygen demand during effort and may increase coronary blood flow, thereby aborting asymptomatic ischemia, which tends to occur at low levels of cardiac oxygen demand. It appears that a greater awareness of the total ischemic burden, i.e., the sum total of symptomatic and asymptomatic and exertional and nonexertional ischemia, may facilitate individualization of therapy for patients with coronary artery disease. Agents that both reduce myocardial oxygen demand and improve coronary blood flow, such as nifedipine, may particularly benefit individuals whose ischemia may be both asymptomatic and symptomatic, and who seem to constitute the majority of patients with coronary artery disease.

Asymptomatic myocardial ischemia in diabetic patients.

The recent recognition of the prevalence of asymptomatic ST-segment depression in patients with coronary artery disease demonstrates the poor sensitivity of using angina as a sign of myocardial ischemia. Possibly the greatest application of ambulatory ST-segment monitoring for the detection of asymptomatic ischemia is in diabetic patients. Coronary artery disease represents the ultimate cause of death in more than half of such patients and usually manifests itself prematurely at an advanced stage. The long-held clinical belief that infarction may be silent, or less painful, in patients with diabetes is supported by several retrospective studies (32 to 42 percent of diabetic patients lack angina at infarction, compared with only 6 to 15 percent of nondiabetic patients). Explanations for this observation have been remarkably deficient in the literature. One group has shown that in diabetic patients with painless infarction, the autonomic nerve fibers of the heart display typical lesions of autonomic neuropathy that may affect afferent sensory impulse transmission compared with those in several matched control groups. Except for a recent report from Italy, there are no data on the prevalence of asymptomatic ischemia in diabetic patients. There are obvious reasons to address this issue more comprehensively: first, given the high incidence of painless myocardial infarction, the frequency of asymptomatic ischemia may be very high; second, because the ability to evaluate patients with standard treadmill testing is limited in patients with peripheral vascular disease and diabetic neuropathy, ambulatory monitoring may be used on a more widespread basis; and third, given the higher than average incidences of sudden death and left ventricular dysfunction in diabetic patients compared with nondiabetic patients, ambulatory monitoring may represent a method of assessing the role of episodic ischemia in explaining these other cardiac events.

Meningitis in an adult caused by Hemophilus influenzae, biotype III.

An elderly woman had an abrupt onset of symptoms consistent with bacterial meningitis without an obvious source of infection. The organism, isolated from the blood and CSF, was a nonserotypeable Hemophilus influenzae, biotype III. To our knowledge, this is the first reported case of meningitis caused by this organism.