Micro-fabricated components for cold atom sensors.

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.

Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides.

The waveguide losses from a range of surface plasmon and double metal waveguides for Ge/Si1-xGex THz quantum cascade laser gain media are investigated at 4.79 THz (62.6 µm wavelength). Double metal waveguides demonstrate lower losses than surface plasmonic guiding with minimum losses for a 10 µm thick active gain region with silver metal of 21 cm-1 at 300 K reducing to 14.5 cm-1 at 10 K. Losses for silicon foundry compatible metals including Al and Cu are also provided for comparison and to provide a guide for gain requirements to enable lasers to be fabricated in commercial silicon foundries. To allow these losses to be calculated for a range of designs, the complex refractive index of a range of nominally undoped Si1-xGex with x = 0.7, 0.8 and 0.9 and doped Ge heterolayers were extracted from Fourier transform infrared spectroscopy measurements between 0.1 and 10 THz and from 300 K down to 10 K. The results demonstrate losses comparable to similar designs of GaAs/AlGaAs quantum cascade laser plasmon waveguides indicating that a gain threshold of 15.1 cm-1 and 23.8 cm-1 are required to produce a 4.79 THz Ge/SiGe THz laser at 10 K and 300 K, respectively, for 2 mm long double metal waveguide quantum cascade lasers with facet coatings.

Low loss Ge-on-Si waveguides operating in the 8-14 µm atmospheric transmission window.

Germanium-on-silicon waveguides were modeled, fabricated and characterized at wavelengths ranging from 7.5 to 11 µm. Measured waveguide losses are below 5 dB/cm for both TE and TM polarization and reach values of ∼ 1 dB/cm for ≥ 10 µm wavelengths for the TE polarization. This work demonstrates experimentally for the first time that Ge-on-Si is a viable waveguide platform for sensing in the molecular fingerprint spectral region. Detailed modeling and analysis is presented to identify the various loss contributions, showing that with practical techniques losses below 1 dB/cm could be achieved across the full measurement range.

Mid-infrared light emission > 3 µm wavelength from tensile strained GeSn microdisks.

GeSn alloys with Sn contents of 8.4 % and 10.7 % are grown pseudomorphically on Ge buffers on Si (001) substrates. The alloys as-grown are compressively strained, and therefore indirect bandgap. Undercut GeSn on Ge microdisk structures are fabricated and strained by silicon nitride stressor layers, which leads to tensile strain in the alloys, and direct bandgap photoluminescence in the 3-5 µm gas sensing window of the electromagnetic spectrum. The use of pseudomorphic layers and external stress mitigates the need for plastic deformation to obtain direct bandgap alloys. It is demonstrated, that the optically pumped light emission overlaps with the methane absorption lines, suggesting that GeSn alloys are well suited for mid-infrared integrated gas sensors on Si chips.

Flow-directed PCA for monitoring networks.

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.

Development of a peripheral nerve stimulator-guided technique for equine pudendal nerve blockade.

The aim of this study was to develop and evaluate a procedure for equine pudendal nerve block using a peripheral nerve locator. In the first experiment, six ponies were used to determine the relationship between elicited muscle contractions (anal, perineal or both) and nerves serving the perineal region (pudendal, caudorectal and perineal nerves) when methylene blue dye was injected using the electrolocation technique. This experiment showed that the pudendal nerve was approached effectively when both anal and perineal twitch were elicited during electrolocation. In a second experiment, seven Thoroughbred horses were used to evaluate the appropriate volume of anaesthetic solution for the nerve block. Immediately after euthanasia, lidocaine/methylene blue solution was injected after positive electrolocation. A stained segment of 2 cm or more of the nerve was considered effective and this was evaluated after dissection. Both 10 and 20 mL per injection site resulted in effective nerve staining. Finally, pudendal nerve block was performed and evaluated in 27 horses admitted for selected reproductive surgical procedures including perineoplasty, urethroplasty, clitorectomy in mares and penile examination, phallectomy and urethrostomy in geldings. Surgical time varied from several minutes to 3 h. The choice between lidocaine, mepivacaine or bupivacaine was based on the duration of analgesia required. In mares and males, a volume of 20 mL and 10 mL, respectively, was injected per site. The use of a peripheral nerve stimulator-guided pudendal nerve block is a feasible, safe and reliable alternative for both epidural and general anaesthesia, to provide peri-operative analgesia in clinical equine patients undergoing specific reproductive surgeries.

Can (1)H MR Spectroscopy be Used to Assess the Success of Uterine Artery Embolisation?

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.

Analysis of Ge micro-cavities with in-plane tensile strains above 2.

Ge on Si micro-disk, ring and racetrack cavities are fabricated and strained using silicon nitride stressor layers. Photoluminescence measurements demonstrate emission at wavelengths ≥ 2.3 µm, and the highest strained samples demonstrate in-plane, tensile strains of > 2 %, as measured by Raman spectroscopy. Strain analysis of the micro-disk structures demonstrate that shear strains are present in circular cavities, which can detrimentally effect the carrier concentration for direct band transitions. The advantages and disadvantages of each type of proposed cavity structure are discussed.

Minimally disruptive medicine: the evidence and conceptual progress supporting a new era of healthcare.

Patients with chronic conditions or multimorbidity, and often their caregivers, have to adjust their lives and mobilise their capacity (ability) to respond to the workload (demands) imposed by treatments and the care of their conditions. There is a continuous and complex interaction between workload and capacity. When capacity proves insufficient to address the treatment workload, creating a burden, patients may place a lower priority on other aspects of their lives, or reduce engagement with healthcare. Guidelines usually focus on disease-centred outcomes without consideration of limited capacity or demanding workload (burden) from treatment regimens. It seems reasonable to consider that healthcare needs reshaping so that care that pursues goals important to patients as well as those suggested by evidence-based medicine. This can be achieved by using shared decision approaches guided by the expertise of clinicians to deliver optimal care while minimising the burden of treatment on patients, their caregivers, and the healthcare system. What we need is minimally disruptive medicine.

Extending the emission wavelength of Ge nanopillars to 2.25 µm using silicon nitride stressors.

The room temperature photoluminescence from Ge nanopillars has been extended from 1.6 µm to above 2.25 µm wavelength through the application of tensile stress from silicon nitride stressors deposited by inductively-coupled-plasma plasma-enhanced chemical-vapour-deposition. Photoluminescence measurements demonstrate biaxial equivalent tensile strains of up to ∼ 1.35% in square topped nanopillars with side lengths of 200 nm. Biaxial equivalent strains of 0.9% are observed in 300 nm square top pillars, confirmed by confocal Raman spectroscopy. Finite element modelling demonstrates that an all-around stressor layer is preferable to a top only stressor, as it increases the hydrostatic component of the strain, leading to an increased shift in the band-edge and improved uniformity over top-surface only stressors layers.

Ge/SiGe quantum confined Stark effect electro-absorption modulation with low voltage swing at λ = 1550 nm.

Low-voltage swing (≤1.0 V) high-contrast ratio (6 dB) electro-absorption modulation covering 1460 to 1560 nm wavelength has been demonstrated using Ge/SiGe quantum confined Stark effect (QCSE) diodes grown on a silicon substrate. The heterolayers for the devices were designed using an 8-band k.p Poisson-Schrödinger solver which demonstrated excellent agreement with the experimental results. Modelling and experimental results demonstrate that by changing the quantum well width of the device, low power Ge/SiGe QCSE modulators can be designed to cover the S- and C-telecommunications bands.

Fungal colonization of haematological patients receiving cytotoxic chemotherapy: emergence of azole-resistant Saccharomyces cerevisiae.

Fungal colonization during cytotoxic chemotherapy was studied in 42 patients with a recent diagnosis of a haematological malignancy. In total, 2759 surveillance cultures were taken from the nostrils, throat, urine, stool and perineal region. Seven hundred and ninety-six positive surveillance cultures (28.9%) yielded 968 fungal isolates. The rate of fungal colonization did not differ between patients with acute leukaemia, patients with other haematological malignancies and control patients in the same ward at admission (71% vs. 67% vs. 80%). Patients with acute leukaemia were colonized at a significantly lower rate in samples from the throat (32%), urine (10%), stool (45%) and perineum (29%) taken during hospitalization when compared with other haematological patients (respective values 58%, 21%, 67% and 45%; P-values 0.001). This could be attributed to differences in the use of antifungal drugs. Although 21/42 (50%) of our patients had multiple-site fungal colonization at the end of follow-up, only one systemic Candida infection was diagnosed. Extensive use of antifungal treatment may have influenced the low incidence of systemic fungal infections during the follow-up. In addition to Candida species, Malassezia furfur, Geotrichum candidum and Saccharomyces cerevisiae were frequently isolated. The rate of S. cerevisiae isolation increased significantly over time after admission (1%, vs. 18% of isolates, P<0.001), suggesting hospital-acquired transmission. These isolates were highly resistant to azole antifungals (MIC90 128 microg/mL for fluconazole and 16 microg/ml, for itraconazole), and caused persistent multiple site colonization in 12 patients. Extensive use of antifungal agents in a haematological ward may keep the incidence of invasive fungal infections low in spite of heavy fungal colonization. However, there may be a risk of emergence of resistant fungal strains.

An outbreak of echovirus type 4 infections and its implications for diagnosis and management in general practice.

Altogether, 133 patients with Echovirus type 4 infection were studied. Presenting illnesses and reasons for referral to hospital were analyzed. The reason for admission was commonly concern about meningitis, but also an unexplained rash or sore throat. More research is needed in general practice in order to clearly elucidate the spectrum of disease caused by Echoviruses.

Behavioral and postural changes observed with use of adaptive seating by clients with multiple handicaps.

Adaptive seating devices (ASDs) are used in the treatment of children with multiple handicaps. This longitudinal study evaluated, through direct observation and parent-guardian assessment, the behavioral changes seen with the use of ASDs and programming. Nineteen individuals with multiple handicaps and developmental disabilities, aged 1 to 6 years, participated as subjects. Data were collected by a trained observer from eight on-site evaluations and from parent-guardian responses to a preequipment and postequipment questionnaire. Evaluations were made every six weeks, starting about three months before and ending about six months after receiving the seating devices. The activities observed were head control, controlled sitting posture, visual tracking, reach, and grasp. Rating scale data were analyzed using an analysis of variance and a Friedman's test. Other data were analyzed descriptively for frequencies and central tendencies. Sitting posture, head control, and grasp improved significantly. Parent perceptions of the equipment indicated that the chairs freed parents from the need to provide support for their children's activities of daily living, which enabled them to participate in other activities with the children and around the home.