Solution-processed PbS quantum dot infrared laser with room-temperature tuneable emission in the optical telecommunications window.

Solution processed semiconductor lasers have achieved much success across the nanomaterial research community, including in organic semiconductors1,2, perovskites3,4 and colloidal semiconductor nanocrystals5,6. The ease of integration with other photonic components, and the potential for upscaling using emerging large area fabrication technologies, such as roll-to-roll7, make these lasers attractive as low-cost photonic light sources that can find use in a variety of applications: integrated photonic circuitry8,9, telecommunications10,11, chemo-/bio-sensing12,13, security14, and lab-on-chip experiments15. However, for fiber-optic or free-space optical (FPO) communications and eye-safe LIDAR applications, room temperature solution-processed lasers have remained elusive. Here we report the first solution processed laser, comprising PbS colloidal quantum dots (CQDs) integrated on a distributed feedback (DFB) cavitiy, with tuneable lasing wavelength from 1.55 µm - 1.65 µm. These lasers operate at room temperature and exhibit linewidths as low as ~0.9 meV.

Simulations of micro-sphere/shell 2D silica photonic crystals for radiative cooling.

Passive daytime radiative cooling has recently become an attractive approach to address the global energy demand associated with modern refrigeration technologies. One technique to increase the radiative cooling performance is to engineer the surface of a polar dielectric material to enhance its emittance at wavelengths in the atmospheric infrared transparency window (8-13 µm) by outcoupling surface-phonon polaritons (SPhPs) into free-space. Here we present a theoretical investigation of new surface morphologies based upon self-assembled silica photonic crystals (PCs) using an in-house built rigorous coupled-wave analysis (RCWA) code. Simulations predict that silica micro-sphere PCs can reach up to 73 K below ambient temperature, when solar absorption and conductive/convective losses can be neglected. Micro-shell structures are studied to explore the direct outcoupling of the SPhP, resulting in near-unity emittance between 8 and 10 µm. Additionally, the effect of material composition is explored by simulating soda-lime glass micro-shells, which, in turn, exhibit a temperature reduction of 61 K below ambient temperature. The RCWA code was compared to FTIR measurements of silica micro-spheres, self-assembled on microscope slides.

Green Perovskite Distributed Feedback Lasers.

A visible perovskite distributed feedback laser is fabricated for the first time. Through the use of nanocrystal pinning, highly luminescent methylammonium lead bromide films are used to produce stable lasers emitting at 550 nm, with a low threshold of 6 µJcm-2. The lasers were able to support multiple polarisations, and could be switched between transverse magnetic and transverse electric mode operation through simple tuning of the distributed feedback grating period.

Translational profiling of retinal ganglion cell optic nerve regeneration in Xenopus laevis.

Unlike adult mammals, adult frogs regrow their optic nerve following a crush injury, making Xenopus laevis a compelling model for studying the molecular mechanisms that underlie neuronal regeneration. Using Translational Ribosome Affinity Purification (TRAP), a method to isolate ribosome-associated mRNAs from a target cell population, we have generated a transcriptional profile by RNA-Seq for retinal ganglion cells (RGC) during the period of recovery following an optic nerve injury. Based on bioinformatic analysis using the Xenopus laevis 9.1 genome assembly, our results reveal a profound shift in the composition of ribosome-associated mRNAs during the early stages of RGC regeneration. As factors involved in cell signaling are rapidly down-regulated, those involved in protein biosynthesis are up-regulated alongside key initiators of axon development. Using the new genome assembly, we were also able to analyze gene expression profiles of homeologous gene pairs arising from a whole-genome duplication in the Xenopus lineage. Here we see evidence of divergence in regulatory control among a significant proportion of pairs. Our data should provide a valuable resource for identifying genes involved in the regeneration process to target for future functional studies, in both naturally regenerative and non-regenerative vertebrates.

Terahertz emission by diffusion of carriers and metal-mask dipole inhibition of radiation.

Terahertz (THz) radiation can be generated by ultrafast photo-excitation of carriers in a semiconductor partly masked by a gold surface. A simulation of the effect taking into account the diffusion of carriers and the electric field shows that the total net current is approximately zero and cannot account for the THz radiation. Finite element modelling and analytic calculations indicate that the THz emission arises because the metal inhibits the radiation from part of the dipole population, thus creating an asymmetry and therefore a net current. Experimental investigations confirm the simulations and show that metal-mask dipole inhibition can be used to create THz emitters.

Discussion of one-D piezoelectric transducer models with loss.

Two, 1-dimensional piezoelectric transducer models are presented that use complex numbers to represent mechanical and dielectric loss. Exact numerical agreement was achieved by avoiding a number of small errors in the literature. A correction to Kino's simplified Mason parallel equivalent circuit is also given. Efficiency is discussed.

Quantitative analysis of reproducible changes in high-voltage electrophotography.

OBJECTIVES: The existence of electromagnetic fields not generated by neuronal action or muscle stimulation remains controversial especially because they are difficulty to detect. We attempted to investigate the existence of electromagnetic fields associated with biologic systems using new image analysis techniques to analyze high-voltage electrophotography. DESIGN/SUBJECTS: Five energy practitioners (three males and two females) and five control subjects (four males and one female) participated in the study. Each practitioner had studied a formal training curriculum and was a professional energy practitioner. Images representing attempts of both energy practitioners and controls to elicit a change in electromagnetic emissions were captured by electrophotographic means. A statistical analysis on the comparison of "ON" vs. "OFF" states for the controls and practitioners in the study was made via digital representation of analogue images. RESULTS: Our interest was threefold: (1) to determine whether corona discharge patterns could be obtained and photographed and be reproducible; (2) to quantify some of the qualitative properties of the coronas; and (3) to determine if individuals can alter, at will, their electrophotographic images. We found a correlation between a change in the electromagnetic emissions for the body and the conscious desire of an energy practitioner to change this state. Analyses of individual finger coronas demonstrate statistically significant differences as analyzed by overall color changes and via analysis of individual sections of the various colors dominating the field. Control subjects were unable to produce statistically significant changes that were reproducible. Physiologic processes, such as changes in skin resistance, sweating, and surface blood constriction, have been suggested as an explanation of the colors and patterns that appear on the film in previous studies, but were not observed in this investigation. CONCLUSIONS: After controlling for the above variables and identifying reproducible and statistically significant changes, we believe the images created in our study represent the interaction of biologically generated electromagnetic fields interacting with the corona discharge created by the electrophotographic device.

Efficacy and safety of an over-the-counter transdermal nicotine patch as an aid for smoking cessation.

OBJECTIVE: To evaluate the efficacy and safety of a transdermal nicotine patch as an aid for smoking cessation in an over-the-counter setting. DESIGN: Multicenter, double-blind, randomized, placebo-controlled trial of 6-week duration with 18 weeks of follow-up. SETTING: Four shopping mall precincts. PARTICIPANTS: The randomized sample consisted of 802 adults (mean age, 39 years) and was 89% white and 54% female. A smoking history of at least 20 cigarettes per day for 1 year and a score of 5 (on a 10-point scale) on a motivational assessment questionnaire were required for enrollment. Poststudy follow-up was limited to those who had quit smoking at the end of 6 weeks. INTERVENTION: Nicotine patches were provided at the shopping mall. Guidance consisted only of package instructions and a smoking cessation self-help booklet. MAIN OUTCOME MEASURES: Quit rates were defined as total abstinence from smoking for 4 consecutive weeks (treatment weeks 3-6), point prevalence smoking status at week 6, or nonsmoker at week 6 and week 24 (6-month postquit date). Smoking status was assessed by diaries, and verification for the first 2 quit rates was obtained by confirmation of carbon monoxide of 8 ppm or less in expired breath. Safety was evaluated by self-reported adverse events. RESULTS: Quit rate was 12% for the active treatment group and 5.5% for the placebo group, based on total abstinence for 4 consecutive weeks (P = .001) compared with quit rates of 19.5% and 7.5% for active treatment and placebo groups, respectively, based on point prevalence data at week 6. At 24 weeks, 8.2% of nonsmokers in the active treatment group and 4.0% in the placebo group remained nonsmokers. At least 1 adverse event was reported by 57% receiving the nicotine patch and 39% receiving placebo (P<.001). CONCLUSIONS: When the nicotine patch was used in an over-the-counter setting, quit rates were comparable to those reported for medical settings. A 2:1 quit rate advantage was achieved at week 6 and was maintained at 24 weeks.

Flow generated around particle clusters in a rotating ultrasonic waveguide.

A chamber cavity, which has a square cross section and pressure-release walls, is used to produce a well-defined, 160-kHz standing ultrasonic field. A suspension of latex microspheres in aqueous metrizamide fills the chamber. The chamber rotates about a horizontal axis producing the centripetal force necessary to contain the buoyant spheres in the axial region. At low particle concentrations, clusters of microspheres form at half-wavelength intervals near the axial positions of acoustic pressure amplitude (p0) minima, as expected because of rotational and acoustic radiation forces. At higher concentrations, additional particle distributions are often seen that suggest the presence of flow. When high concentrations of larger particles are used, small clusters also form at axial positions of p0 maxima. Theory for acoustic streaming in a rotating fluid predicts flow speeds that are too small to account for the observed flow. Reasonable agreement with observations is obtained using a theory for flow generated by the buoyant gravitational force acting on the clusters.

Self-hypnosis reduces anxiety following coronary artery bypass surgery. A prospective, randomized trial.

OBJECTIVE: The role of complementary medicine techniques has generated increasing interest in today's society. The purpose of our study was to evaluate the effects of one technique, self-hypnosis, and its role in coronary artery bypass surgery. We hypotesize that self-hypnosis relaxation techniques will have a positive effect on the patient's mental and physical condition following coronary artery bypass surgery. EXPERIMENTAL DESIGN: A prospective, randomized trial was conducted. Patients were followed beginning one day prior to surgery until the time of discharge from the hospital. SETTING: The study was conducted at Columbia Presbyterian Medical Center, a large tertiary care teaching institution. PATIENTS: All patients undergoing first-time elective coronary artery bypass surgery were eligible. A total of 32 patients were randomized into two groups. INTERVENTIONS: The study group was taught self-hypnosis relaxation techniques preoperatively, with no therapy in the control group. MEASURES: Outcome variables studied included anesthetic requirements, operative parameters, postoperative pain medication requirements, quality of life, hospital stay, major morbidity and mortality. RESULTS: Patients who were taught self-hypnosis relaxation techniques were significantly more relaxed postoperatively compared to the control group (p=0.032). Pain medication requirements were also significantly less in patients practising the self-hypnosis relaxation techniques that those who were noncompliant (p=0.046). No differences were noted in intraoperative parameters, morbidity or mortality. CONCLUSION: This study demonstrates the beneficial effects self-hypnosis relaxation techniques on patients undergoing coronary artery bypass surgery. It also provides a framework to study complementary techniques and the limitations encountered.

Chlamydial cervicitis and urethritis: single dose treatment compared with doxycycline for seven days in community based practises.

STUDY GOAL: To compare the efficacy and safety of single 1 g oral azithromycin with doxycycline, 100 mg twice daily for seven days for treatment of uncomplicated urogenital chlamydial infection. STUDY DESIGN: Randomised, unblinded, comparative trial, involving 597 patients demonstrating clinical evidence of genital chlamydia and a positive non-culture assay for Chlamydia trachomatis. RESULTS: Among the azithromycin- and doxycycline-treated patients 61% and 60%, respectively, were asymptomatic within one week after the first dose. At two weeks, these figures increased to 86% and 83%, respectively. Bacteriological eradication, based on a negative assay, occurred in 338 (97%) of 347 azithromycin-treated patients and 161 (99%) of 163 doxycycline-treated patients. CONCLUSION: Treatment of uncomplicated chlamydial cervicitis and urethritis with single 1 g oral azithromycin is equivalent to standard therapy with doxycycline. Drug-related adverse events were approximately twice as common as previously reported for both drugs.

The effects of self-hypnosis on quality of life following coronary artery bypass surgery: preliminary results of a prospective, randomized trial.

The effects of complementary techniques and alternative medicine on allopathic therapies is generating much interest and research. To properly evaluate these techniques, well controlled studies are needed to corroborate the findings espoused by individuals practicing complementary medicine therapies. To this end, we evaluated the role of one of these therapies, self-hypnosis relaxation techniques, in a prospective, randomized trial to study its effects on quality of life after coronary artery bypass surgery. Subjects were randomized to a control group or a study group. Study group patients were taught self-hypnosis relaxation techniques the night prior to surgery. The control group received no such treatment. Patients then underwent routine cardiac management and care. The main endpoint of our study was quality of life, assessed by the Profile of Moods Scale. Results demonstrated that patients undergoing self-hypnosis the night prior to coronary artery bypass surgery were significantly more relaxed than the control group (p = 0.0317). Trends toward improvement were also noted in depression, anger, and fatigue. This study demonstrates the beneficial effects of self-hypnosis relaxation techniques on coronary surgery. This study also identifies endpoints and a study design that can be used to assess complementary medicine therapies. Results of this preliminary investigation are encouraging and demonstrate a need for further well-controlled studies.

Phylogenetic relationships between Toxoplasma and Sarcocystis deduced from a comparison of 18S rDNA sequences.

The current taxonomy of parasites in the genus Sarcocystis is largely based on morphological characteristics as well as on host specificity and life-cycle structure. Recently, phylogenetic analyses of partial ribosomal RNA (rRNA) sequences provided support for paraphyly of Sarcocystis. We have tested the validity of this hypothesis by sequencing the complete 18S rRNA genes of Sarcocystis arieticanis, Sarcocystis gigantea and Sarcocystis tenella and comparing them with gene sequences derived from other taxa of the phylum Apicomplexa. The results obtained from this study do not reject the hypothesis of monophyly of Sarcocystis species, although the bootstrap data were inconclusive for some species.

Ultrasonic manipulation of particles and cells. Ultrasonic separation of cells.

Cells or particles suspended in a sonic standing wave field experience forces which concentrate them at positions separated by half a wavelength. The aims of the study were: (1) To optimise conditions and test theoretical predictions for ultrasonic concentration and separation of particles or cells. (2) To investigate the scale-up of experimental systems. (3) To establish the maximum acoustic pressure to which a suspension might be exposed without inducing order-disrupting cavitation. (4) To compare the efficiencies of techniques for harvesting concentrated particles. The primary outcomes were: (1) To design of an acoustic pressure distribution within cylindrical containers which led to uniformly repeating sound pressure patterns throughout the containers in the standing wave mode, concentrated suspended eukaryotic cells or latex beads in clumps on the axis of wide containers, and provided uniform response of all particle clumps to acoustic harvesting regimes. Theory for the behaviour (e.g. movement to different preferred sites) of particles as a function of specific gravity and compressibility in containers of different lateral dimensions was extended and was confirmed experimentally. Convective streaming in the container was identified as a variable requiring control in the manipulation of particles of 1 micron or smaller size. (2) Consideration of scale-up from the model 10 ml volume led to the conclusion that flow systems in intermediate volume containers have more promise than scaled up batch systems. (3) The maximum acoustic pressures applicable to a suspension without inducing order-disrupting cavitation or excessive conductive streaming at 1 MHz and 3 MHz induce a force equivalent to a centrifugal field of about 10(3) g. (4) The most efficient technique for harvesting concentrated particles was the introduction of a frequency increment between two transducers to form a slowly sweeping pseudo-standing wave. The attractive inter-droplet ultrasonic standing wave force was employed to enhance the rate of aqueous biphasic cell separation and harvesting. The results help clarify the particle size, concentration, density and compressibility for which standing wave separation techniques can contribute either on a process engineering scale or on the scale of the manipulation of small particles for industrial and medical diagnostic procedures.

Transport and harvesting of suspended particles using modulated ultrasound.

Polystyrene particles of 9 microns diameter were acoustically concentrated along the axis of a water-filled cylindrical waveguide containing a 3 MHz standing wave field. Modulation of the acoustic field enabled transport of the concentrated particles in the axial direction. Four modulations were investigated: 1, a fixed frequency difference introduced between two transducers; 2, ramping the transducer frequency; 3, tone burst, i.e. sound that is pulsed on and off, allowing intermittent sedimentation under gravity; and 4, switching the sound off to allow continuous sedimentation. The most efficient transport (leaving the fewest particles in suspension) of clumps to one end of the container was achieved with method 1 above. In this system the maximum speed of transport of the axial clumps was 24 mm s-1. A theory developed here for the transport of particles in a pseudo (i.e. slowly moving) standing wave field predicts an upper limit, which increases with particle size, for the speed of an entrained body. For a single 9 microns diameter particle in a field with a spatial peak pressure amplitude of 0.4 MPa this speed would be 0.5 mm s-1. The higher experimental speeds observed here emphasize the value of acoustically concentrating particles into relatively large clumps prior to initiating transport.

A rotating ultrasonic waveguide for studying acoustic radiation forces on particles.

An apparatus was designed to allow a suspension of biological cells to be subjected to a well-defined, 160-kHz standing ultrasonic field while being viewed through a stereo microscope. Cell positions were recorded either photographically or by means of a video camera. The chamber cavity, which has a square cross section and pressure-release walls, acts as a single-mode acoustic waveguide. The well-defined single-mode field is achieved through use of a special design involving air-filled chamber windows. Aqueous metrizamide solution is used to fill the ultrasonic chamber because it has a unique combination of properties, including low viscosity, low osmolarity, and high density. The chamber rotates about its axis (whose inclination can be varied) producing the centripetal force necessary to contain the buoyant cells in the axial region. Observations were made on stroboscopically illuminated suspensions both of latex microspheres and of red blood cells. The particles formed groups at half-wavelength intervals along the rotation axis near positions of acoustic pressure-amplitude minima. The position and shape of these groupings are explained by a scalar-potential theory for noninteracting particles that considers gravitational, rotational, and acoustic radiation forces on the particles.

Acoustic streaming in a rotating fluid.

Acoustic streaming theory is derived that is applicable to a fluid that is slow moving in a reference frame that rotates with a constant angular velocity omega. A simplified streaming equation is obtained for the special case in which the acoustic angular frequency omega is large relative to omega, and the change in fluid density due to rotation alone is negligible. For this special case it is shown that the "driving force" for the acoustic streaming is independent of omega. Thus, if no acoustic streaming is present in a fluid system that is stationary, then no steady-state acoustic streaming is predicted for a similar system that rotates with constant angular velocity. For a system in which acoustic streaming is present, the flow behavior depends on the relative magnitudes of the Coriolis forces and the viscous forces. If the Ekman number is large (that is, the viscous force dominates) then the predicted flow is identical to that which would exist in a stationary system. If, on the other hand, the Ekman number is small then the Coriolis force dominates and the component of flow in the direction of the axis of rotation can be much smaller in the rotating system than in a similar system at rest.