Search

A new epitaxial layer design with a double mode expander layer, high refractive index claddings, and an aluminum-free active area has been used to demonstrate distributed feedback lasers operating at 778.1 nm wavelength with reduced Lorentzian linewidth aimed at miniature atomic clock applications. The design also reduces the vertical beam divergence to improve the modal matching with optical fibers as well as maintain the high power output and reduce the emission linewidth. The lasers demonstrate single-mode operation with an over 35 dB side-mode suppression ratio, a power output ≤58 mW, a coupling efficiency to tapered fibers ≤40%, and a Lorentzian linewidth of 3.7 kHz. The performance allowed the free-running distributed feedback lasers to demonstrate spectroscopy of Rb vapor, which resolved the 85Rb and 87Rb two-photon transitions. [ABSTRACT FROM AUTHOR]

A Ge-SiGe multiple quantum well structure created by low energy plasma enhanced chemical vapour deposition, with nominal well thickness of 5.4 nm separated by 3.6 nm SiGe spacers, is analysed quantitatively using scanning transmission electron microscopy. Both high angle annular dark field imaging and electron energy loss spectroscopy show that the interfaces are not completely sharp, suggesting that there is some intermixing of Si and Ge at each interface. Two methods are compared for the quantification of the spectroscopy datasets: a self-consistent approach that calculates binary substitutional trends without requiring experimental or computational κ-factors from elsewhere and a standards-based cross sectional calculation. Whilst the cross section approach is shown to be ultimately more reliable, the self-consistent approach provides surprisingly good results. It is found that the Ge quantum wells are actually about 95% Ge and that the spacers, whilst apparently peaking at about 35% Si, contain significant interdiffused Ge at each side. This result is shown to be not just an artefact of electron beam spreading in the sample, but mostly arising from a real chemical interdiffusion resulting from the growth. Similar results are found by use of X-ray diffraction from a similar area of the sample. Putting the results together suggests a real interdiffusion with a standard deviation of about 0.87nm, or put another way—a true width defined from 10%–90% of the compositional gradient of about 2.9 nm. This suggests an intrinsic limit on how sharp such interfaces can be grown by this method and, whilst 95% Ge quantum wells (QWs) still behave well enough to have good properties, any attempt to grow thinner QWs would require modifications to the growth procedure to reduce this interdiffusion, in order to maintain a composition of ≥95% Ge. [ABSTRACT FROM AUTHOR]

Laser cooled atoms have proven transformative for precision metrology, playing a pivotal role in state-of-the-art clocks and interferometers and having the potential to provide a step-change in our modern technological capabilities. To successfully explore their full potential, laser cooling platforms must be translated from the laboratory environment and into portable, compact quantum sensors for deployment in practical applications. This transition requires the amalgamation of a wide range of components and expertise if an unambiguously chip-scale cold atom sensor is to be realized. We present recent developments in cold-atom sensor miniaturization, focusing on key components that enable laser cooling on the chip-scale. The design, fabrication, and impact of the components on sensor scalability and performance will be discussed with an outlook to the next generation of chip-scale cold atom devices. [ABSTRACT FROM AUTHOR]

Purpose: Absence of contrast on contrast enhanced MRI (CEMRI) and reduction in uterine volume at 6 months post-uterine artery embolisation (UAE) currently indicate the successful disruption of the fibroid blood supply by UAE. This study assesses whether (1)H MR spectroscopy ((1)H MRS) can also indicate the success of UAE. Method: 20 patients with symptomatic fibroids were randomised 1:1 to undergo UAE with either Gelfoam or Embospheres. CEMRI and spectra (1.5 T) were acquired pre-, 24-h and 6 months post-UAE. LCModel was used to detect significant levels of choline, creatine and lactate in fibroid spectra. Uterine volumes were measured and paired t tests (p < 0.05) assessed volume reduction over time. Qualitative assessments of CEMRI were performed. Results: Choline was detected in 17/18 spectra pre-UAE, 12/14 at 24-h and 6/16 at 6 months post-UAE. Choline was not detected in the 7/7 spectra available for the Embospheres group at 6 months. These fibroids were non-enhancing on CEMRI and associated with a significant reduction in mean uterine volume at 6 months (mean/min/max 396.5/84.1/997.5 cm(3), p = 0.003). Choline was detected in 6/9 fibroid spectra available for the Gelfoam group at 6 months. Of these fibroids, four demonstrated persistent enhancement on CEMRI and two were non-enhancing. This group did not demonstrate significant uterine volume reduction (mean/min/max 117.2/-230.6/382.6 cm(3), p = 0.15). The negative minimum value indicates fibroid growth. Conclusions: This study has demonstrated the potential of (1)H MRS to provide an additional marker of the success of UAE. [ABSTRACT FROM AUTHOR]

Mid-infrared intersubband absorption from p-Ge quantum wells with Si0.5Ge0.5 barriers grown on a Si substrate is demonstrated from 6 to 9 µm wavelength at room temperature and can be tuned by adjusting the quantum well thickness. Fourier transform infra-red transmission and photoluminescence measurements demonstrate clear absorption peaks corresponding to intersubband transitions among confined hole states. The work indicates an approach that will allow quantum well intersubband photodetectors to be realized on Si substrates in the important atmospheric transmission window of 8-13 µm. [ABSTRACT FROM AUTHOR]

A self doping contact consisting of a silver/antimony alloy that produces an Ohmic contact to moderately doped n-type germanium (doped to a factor of four above the metal-insulator transition) has been investigated. An evaporation of a mixed alloy of Ag/Sb (99%/1%) onto n-Ge (ND = 1 × 1018 cm-3) annealed at 400°C produces an Ohmic contact with a measured specific contact resistivity of (1:1±0.2) × 10-5 Ω-cm². It is proposed that the Ohmic behaviour arises from an increased doping concentration at the Ge surface due to the preferential evaporation of Sb confirmed by transmission electron microscope analysis. It is suggested that the doping concentration has increased to a level where field emission will be the dominate conduction mechanism. This was deduced from the low temperature electrical characterisation of the contact, which exhibits Ohmic behaviour down to a temperature of 6.5 K. [ABSTRACT FROM AUTHOR]

Aims To develop, describe and evaluate clinical applicability of pudendal nerve block using a peripheral nerve locator. Methods In a pilot study, 6 ponies were used to determine the correlation between nerves serving the perineal region (namely pudendal, caudorectal and perineal nerves) and the muscle contractions observed when an electrolocation technique was used. After appropriate electrolocation a small volume of lidocaine/methylene blue solution was injected under general anaesthesia. The dye location relative to the specified nerves was examined after humane euthanasia followed by dissection of the relevant region. In a second experiment, 7 Thoroughbred horses were used to evaluate the appropriate volume of lidocaine solution for the nerve block. Lidocaine/methylene blue solution was injected after positive electrolocation immediately (5-40 min) after euthanasia. A stained segment of 2 cm or more of the nerve was deemed to be sufficient and was evaluated after dissection. Finally, evaluation of a bilateral pudendal nerve block was used to provide anaesthesia and analgesia in 10 clinical cases involving both mares and geldings. Results Anal twitch alone was associated with injection of the caudal rectal nerve, whereas combined twitch of the anus and perineum was required for reliable location and injection of the pudendal nerve. Injection was more accurate in standing rather than laterally recumbent horses. A volume of 10-20 ml bilaterally, reliably provided at least 60 min of clinical analgesia for perineal surgery. Procedures satisfactorily completed included; urethral extension and perineal body repair in mares and penile examination, removal of penile tumours and penile amputation in male patients. Conclusions and practical significance Pudendal nerve block is a practical and effective alternative to epidural analgesia for selected standing surgical procedures of the reproductive tract in male and female horses. Ethical animal research The Cornell University Institutional Animal Care and Use Committee approved the project and informed client consent was obtained. Sources of funding: None. Competing interests: None. [ABSTRACT FROM AUTHOR]

Kathleen Gallacher describes how decisions made over the care of one patient have informed practice. [ABSTRACT FROM AUTHOR]

A low temperature nickel process has been developed that produces Ohmic contacts to n-type germanium with specific contact resistivities down to (2.3 ± 1.8) × 10-7 Ω-cm2 for anneal temperatures of 340 °C. The low contact resistivity is attributed to the low resistivity NiGe phase which was identified using electron diffraction in a transmission electron microscope. Electrical results indicate that the linear Ohmic behaviour of the contact is attributed to quantum mechanical tunnelling through the Schottky barrier formed between the NiGe alloy and the heavily doped n-Ge. [ABSTRACT FROM AUTHOR]

Measurements recorded over monitoring networks often possess spatial and temporal correlation inducing redundancies in the information provided. For river water quality monitoring in particular, flow-connected sites may likely provide similar information. This paper proposes a novel approach to principal components analysis to investigate reducing dimensionality for spatiotemporal flow-connected network data in order to identify common spatiotemporal patterns. The method is illustrated using monthly observations of total oxidized nitrogen for the Trent catchment area in England. Common patterns are revealed that are hidden when the river network structure and temporal correlation are not accounted for. Such patterns provide valuable information for the design of future sampling strategies. [ABSTRACT FROM AUTHOR]

Electroluminescence from strained n-Ge quantum well light emitting diodes grown on a silicon substrate are demonstrated at room temperature. Electroluminescence characterisation demonstrates two peaks around 1.55 μm and 1.8 μm, which correspond to recombination between the direct and indirect transitions, respectively. The emission wavelength can be tuned by around 4% through changing the current density through the device. The devices have potential applications in the fields of optical interconnects, gas sensing, and healthcare. [ABSTRACT FROM AUTHOR]

Abstract Introduction and aims Heart failure (HF) is as ‘malignant’ as many common cancers. It is known that end stage heart failure (ESHF) symptoms have a negative impact on the daily lives of patients who also feel unsupported. The aim of this study is to examine patient experiences of managing their condition, with a particular focus on their ‘treatment burden’, defined as the ‘work’ they do to manage their condition, including reference to the services they use and how they negotiate and mobilize these. It is essential to understand these issues if we are to be able to design more patient centred services. Methods This study involves semi-structured interviews with ESHF patients focusing on the work they do to manage and ‘live’ with their condition. Qualitative data analysed using framework methods informed by Normalization Process Theory. Inclusion criteria: at least Grade 3 or 4 NYHA classification HF; who have ongoing symptoms despite optimal therapy; and have a history of admissions for this condition. Results 33 patients identified, 21 consenting to participation. 16 male; 5 female. Patients described a vast range of treatment burdens many which were secondary to the health care systems and the lack of a patient centred approach. Issues raised included: the work imposed by disorganised systems of care necessitating multiple attendances for check-ups and investigations; lack of continuity; inadequate communication between health professionals; polypharmacy; and difficulties accessing services. Conclusions This study has highlighted a range of challenges for patients posed by current health care systems, highlighting clear points for intervention. [ABSTRACT FROM PUBLISHER]