Surface-normal illuminated pseudo-planar Ge-on-Si avalanche photodiodes with high gain and low noise.

Germanium-on-Silicon (Ge-on-Si) avalanche photodiodes (APDs) are of considerable interest as low intensity light detectors for emerging applications. The Ge absorption layer detects light at wavelengths up to ≈ 1600 nm with the Si acting as an avalanche medium, providing high gain with low excess avalanche noise. Such APDs are typically used in waveguide configurations as growing a sufficiently thick Ge absorbing layer is challenging. Here, we report on a new vertically illuminated pseudo-planar Ge-on-Si APD design utilizing a 2 µm thick Ge absorber and a 1.4 µm thick Si multiplication region. At a wavelength of 1550 nm, 50 µm diameter devices show a responsivity of 0.41 A/W at unity gain, a maximum avalanche gain of 101 and an excess noise factor of 3.1 at a gain of 20. This excess noise factor represents a record low noise for all configurations of Ge-on-Si APDs. These APDs can be inexpensively manufactured and have potential integration in silicon photonic platforms allowing use in a variety of applications requiring high-sensitivity detectors at wavelengths around 1550 nm.

Tradeoffs in the sensory brain between diurnal and nocturnal rodents.

INTRODUCTION: Transitions in temporal niche have occurred many times over the course of mammalian evolution. These are associated with changes in sensory stimuli available to animals, particularly with visual cues, because levels of light are so much higher during the day than night. This relationship between temporal niche and available sensory stimuli elicits the expectation that evolutionary transitions between diurnal and nocturnal lifestyles will be accompanied by modifications of sensory systems that optimize the ability of animals to receive, process, and react to important stimuli in the environment. METHODS: This study examines the influence of temporal niche on investment in sensory brain tissue of 13 rodent species (five diurnal; eight nocturnal). Animals were euthanized and the brain immediately frozen on dry ice; olfactory bulbs were subsequently dissected and weighed, and the remaining brain was weighed, sectioned, and stained. Stereo Investigator was used to calculate volumes of four sensory regions that function in processing visual (lateral geniculate nucleus, superior colliculus) and auditory (medial geniculate nucleus, inferior colliculus) information. A phylogenetic framework was used to assess the influence of temporal niche on the relative sizes of these brain structures and of olfactory bulb weights. RESULTS: Compared to nocturnal species, diurnal species had larger visual regions, whereas nocturnal species had larger olfactory bulbs than their diurnal counterparts. Of the two auditory structures examined, one (medial geniculate nucleus) was larger in diurnal species, while the other (inferior colliculus) did not differ significantly with temporal niche. CONCLUSION: Our results indicate a possible indirect association between temporal niche and auditory investment and suggest probable tradeoffs of investment between olfactory and visual areas of the brain, with diurnal species investing more in processing visual information and nocturnal species investing more in processing olfactory information.

Protein-Engineered Fibers For Drug Encapsulation Traceable via 19F Magnetic Resonance.

Theranostic materials research is experiencing rapid growth driven by the interest in integrating both therapeutic and diagnostic modalities. These materials offer the unique capability to not only provide treatment but also track the progression of a disease. However, to create an ideal theranostic biomaterial without compromising drug encapsulation, diagnostic imaging must be optimized for improved sensitivity and spatial localization. Herein, we create a protein-engineered fluorinated coiled-coil fiber, Q2TFL, capable of improved sensitivity to 19F magnetic resonance spectroscopy (MRS) detection. Leveraging residue-specific noncanonical amino acid incorporation of trifluoroleucine (TFL) into the coiled-coil, Q2, which self-assembles into nanofibers, we generate Q2TFL. We demonstrate that fluorination results in a greater increase in thermostability and 19F magnetic resonance detection compared to the nonfluorinated parent, Q2. Q2TFL also exhibits linear ratiometric 19F MRS thermoresponsiveness, allowing it to act as a temperature probe. Furthermore, we explore the ability of Q2TFL to encapsulate the anti-inflammatory small molecule, curcumin (CCM), and its impact on the coiled-coil structure. Q2TFL also provides hyposignal contrast in 1H MRI, echogenic signal with high-frequency ultrasound and sensitive detection by 19F MRS in vivo illustrating fluorination of coiled-coils for supramolecular assembly and their use with 1H MRI, 19F MRS and high frequency ultrasound as multimodal theranostic agents.

Improved Process for the Preparation of Naloxegol Oxalate, an Opiod Receptor Antagonist.

The present article discloses an improved and robust commercial process of the modern medicine naloxegol oxalate, which is used to treat opioid-induced constipation. The synthesis originates from the easily available key starting material, viz., naloxone, and ends with the oxalate salt of naloxegol (a pharmaceutically acceptable salt). This novel route has a very high yield and purity greater than 99.5%, substantially free from impurities (less than 1%).

Investigation of temperature sensitivity of a MEMS gravimeter based on geometric anti-spring.

This paper describes a technique for temperature sensitivity or thermal sag measurements of a geometric anti-spring based microelectromechanical system (MEMS) gravimeter (Wee-g). The Wee-g MEMS gravimeter is currently fabricated on a (100) silicon wafer using standard micro-nano fabrication techniques. The thermal behavior of silicon indicates that the Young's modulus of silicon decreases with increase in temperature (∼64 ppm/K). This leads to a softening of the silicon material, resulting in the proof mass displacing (or sagging) under the influence of increasing temperature. It results in a change in the measured gravity, which is expressed as temperature sensitivity in terms of change in gravity per degree temperature. The temperature sensitivity for the silicon based MEMS gravimeter is found to be 60.14-64.87, 61.76, and 62.76 µGal/mK for experimental, finite element analysis (FEA) simulation, and analytical calculations, respectively. It suggests that the gravimeter's temperature sensitivity is dependent on the material properties used to fabricate the MEMS devices. In this paper, the experimental measurements of thermal sag are presented along with analytical calculations and simulations of the effect using FEA. The bespoke optical measurement system to quantify the thermal sag is also described. The results presented are an essential step toward the development of temperature insensitive MEMS gravimeters.

Occurrence of dental emergency events in Primary Health Care services.

The aim of this study was to describe the occurrence of dental emergency and its association with individual factors and primary health care services. A follow-up study was conducted with data extracted from an exploratory study about the classification of dental care needs over time according to a care framework. There were included 1831 patients of five services. The outcome was the occurrence of dental emergency analyzed according to sex, age, skin color, service and maximum waiting time for dental care. A multivariate analysis with Poisson regression was used to estimate weighted prevalence ratio (PR) with 95% Confidence Intervals (CI) and survival analysis was conducted. The prevalence of dental emergency was 12.6%, varying according to age (13-19: PRa =1.79 (95%CI: 1.0-3.21); 20-65:PRa = 2.71 (95%CI: 1.73-4.26); Over 65: PRa = 2.51 (95%CI: 1.41-4.46)) and Primary Health Care service (FHS 2: PRa = 2.20 (95%CI: 1.37-3.53),FHS 3: PRa = 1.43 (95%CI: 0.90-2.27); FHS 4: PRa = 3.25 (95%CI: 2.15-4.92),FHS 5: PRa = 2.49 (95%CI: 1.56-3.97)) For 231 cases classified as emergency, the failure rate was 7.4%. For 214 cases of emergency, the non-continuity after appointment rate was 53.7%. The incidence of dental emergency was 8.3% and recurrence was 7.2%. Considering all 262 emergency cases attended, the resolution rate was 93.5% and most cases (n = 252, 96.1%) received care within one day. The results point to high effectiveness in emergency dental care within Primary Health Care services. There are indications of the need for improvements in retention and continuity of care.

A 19 day earth tide measurement with a MEMS gravimeter.

The measurement of tiny variations in local gravity enables the observation of subterranean features. Gravimeters have historically been extremely expensive instruments, but usable gravity measurements have recently been conducted using MEMS (microelectromechanical systems) sensors. Such sensors are cheap to produce, since they rely on the same fabrication techniques used to produce mobile phone accelerometers. A significant challenge in the development of MEMS gravimeters is maintaining stability over long time periods, which is essential for long term monitoring applications. A standard way to demonstrate gravimeter stability and sensitivity is to measure the periodic elastic distortion of the Earth due to tidal forces-the Earth tides. Here, a 19 day measurement of the Earth tides, with a correlation coefficient to the theoretical signal of 0.975, has been presented. This result demonstrates that this MEMS gravimeter is capable of conducting long-term time-lapse gravimetry, a functionality essential for applications such as volcanology.

Organic carbon concentrations in 3.5-billion-year-old lacustrine mudstones of Mars.

The Sample Analysis at Mars instrument stepped combustion experiment on a Yellowknife Bay mudstone at Gale crater, Mars revealed the presence of organic carbon of Martian and meteoritic origins. The combustion experiment was designed to access refractory organic carbon in Mars surface sediments by heating samples in the presence of oxygen to combust carbon to CO2. Four steps were performed, two at low temperatures (less than ∼550 °C) and two at high temperatures (up to ∼870 °C). More than 950 µg C/g was released at low temperatures (with an isotopic composition of δ13C = +1.5 ± 3.8‰) representing a minimum of 431 µg C/g indigenous organic and inorganic Martian carbon components. Above 550 °C, 273 ± 30 µg C/g was evolved as CO2 and CO (with estimated δ13C = -32.9‰ to -10.1‰ for organic carbon). The source of high temperature organic carbon cannot be definitively confirmed by isotopic composition, which is consistent with macromolecular organic carbon of igneous origin, meteoritic infall, or diagenetically altered biomass, or a combination of these. If from allochthonous deposition, organic carbon could have supported both prebiotic organic chemistry and heterotrophic metabolism at Gale crater, Mars, at ∼3.5 Ga.

Culture and understanding the role of feedback for health professions students: realist synthesis protocol.

INTRODUCTION: Clinical education has moved to a 'competency-based' model with an emphasis on workplace-based learning and assessment which, in turn, depends on feedback to be effective. Further, the understanding of feedback has changed from information about a performance directed to the learner performing the task, to a dialogue, which enables the learner to act and develop.In health professional education, feedback is a complex interaction between trainee, supervisor and the healthcare system. Most published research on feedback in health professional education originates in Europe and North America. Our interest is on the impact of Culture on this process, particularly in the context of Asian cultures.The (scientific) realist approach of Pawson and Tilley provides a means to examine complex interventions in social situations, and thus is an appropriate lens to use for this study. This is a protocol for a realist synthesis which asks how, why and in what circumstances do Asian Cultures influence health professional trainees to seek, respond to and use feedback given in the clinical environment, if at all. METHODS AND ANALYSIS: An initial search was performed to help define the scope of the review question and develop our initial programme theory. The formal electronic search was carried out in February 2020 and included: CINAHL, ERIC, Medline and PsycInfo, and repeated in October 2020. Retrieved articles were imported into Covidence for screening and data extraction, after which components of the Context-Mechanisms-Outcomes configurations will be sought to refine the initial programme theory. ETHICS AND DISSEMINATION: As this study is a literature review, ethics approval is not required.The findings will be documented in line with the RAMESES (Realist And MEta-narrative Evidence Syntheses: Evolving Standards) publications standards for Realist syntheses, and we plan to disseminate the findings by means of a peer-reviewed journal article and conference presentation(s).

Occurrence of dental emergency events in Primary Health Care services

Abstract The aim of this study was to describe the occurrence of dental emergency and its association with individual factors and primary health care services. A follow-up study was conducted with data extracted from an exploratory study about the classification of dental care needs over time according to a care framework. There were included 1831 patients of five services. The outcome was the occurrence of dental emergency analyzed according to sex, age, skin color, service and maximum waiting time for dental care. A multivariate analysis with Poisson regression was used to estimate weighted prevalence ratio (PR) with 95% Confidence Intervals (CI) and survival analysis was conducted. The prevalence of dental emergency was 12.6%, varying according to age (13-19: PRa =1.79 (95%CI: 1.0-3.21); 20-65:PRa = 2.71 (95%CI: 1.73-4.26); Over 65: PRa = 2.51 (95%CI: 1.41-4.46)) and Primary Health Care service (FHS 2: PRa = 2.20 (95%CI: 1.37-3.53),FHS 3: PRa = 1.43 (95%CI: 0.90-2.27); FHS 4: PRa = 3.25 (95%CI: 2.15-4.92),FHS 5: PRa = 2.49 (95%CI: 1.56-3.97)) For 231 cases classified as emergency, the failure rate was 7.4%. For 214 cases of emergency, the non-continuity after appointment rate was 53.7%. The incidence of dental emergency was 8.3% and recurrence was 7.2%. Considering all 262 emergency cases attended, the resolution rate was 93.5% and most cases (n = 252, 96.1%) received care within one day. The results point to high effectiveness in emergency dental care within Primary Health Care services. There are indications of the need for improvements in retention and continuity of care.

Risk Factors of Forced Take-Off in Dairy Cows Milked Three Times per Day in A Rotary Milking Parlor: A Case Control Study.

The aims of the research were to: (1) describe a protocol for the identification of cows that are subjected repeatedly to a forced retraction event at the end of milking; (2) study risk factors of repeated forced take-off (RFTO); and (3) assess the average milk flow rate at which the forced retraction event occurred. In a retrospective study, we collected milk flow data over a 1-week period from a 4300-cow dairy with a rotary milking parlor and a thrice-daily milking schedule. We identified 109 cases of RFTO and 2467 controls. A multivariable logistic regression model revealed associations of parity, stage of lactation, average daily milk production, and milking speed with RFTO. Cows in parity 3 or greater, animals ≤100 days in milk, high-producing animals, and cows with low milking speed had higher odds of RFTO. The average (least squares means (95% CI)) milk flow rates at the time of removal of the milking unit were 2.1 (2.0-2.1) kg/min in milking observations that were terminated with the forced retract and 1.5 (1.4-1.5) kg/min when milking units were removed with the automatic cluster remover. Future research to better understand the effect of RFTO on milk production, udder health, and animal well-being is warranted.

Faceting of Si and Ge crystals grown on deeply patterned Si substrates in the kinetic regime: phase-field modelling and experiments.

The development of three-dimensional architectures in semiconductor technology is paving the way to new device concepts for various applications, from quantum computing to single photon avalanche detectors. In most cases, such structures are achievable only under far-from-equilibrium growth conditions. Controlling the shape and morphology of the growing structures, to meet the strict requirements for an application, is far more complex than in close-to-equilibrium cases. The development of predictive simulation tools can be essential to guide the experiments. A versatile phase-field model for kinetic crystal growth is presented and applied to the prototypical case of Ge/Si vertical microcrystals grown on deeply patterned Si substrates. These structures, under development for innovative optoelectronic applications, are characterized by a complex three-dimensional set of facets essentially driven by facet competition. First, the parameters describing the kinetics on the surface of Si and Ge are fitted on a small set of experimental results. To this goal, Si vertical microcrystals have been grown, while for Ge the fitting parameters have been obtained from data from the literature. Once calibrated, the predictive capabilities of the model are demonstrated and exploited for investigating new pattern geometries and crystal morphologies, offering a guideline for the design of new 3D heterostructures. The reported methodology is intended to be a general approach for investigating faceted growth under far-from-equilibrium conditions.

Feedback after OSCE: A comparison of face to face versus an enhanced written feedback.

BACKGROUND: The Objective Structured Clinical Exam (OSCE) is a useful means of generating meaningful feedback. OSCE feedback may be in various forms (written, face to face and audio or video recordings). Studies on OSCE feedback are uncommon, especially involving Asian medical students. METHODS: We compared two methods of OSCE feedback delivered to fourth year medical students in Malaysia: (i) Face to face (FTF) immediate feedback (semester one) (ii) Individualised enhanced written (EW) feedback containing detailed scores in each domain, examiners' free text comments and the marking rubric (semester two). Both methods were evaluated by students and staff examiners, and students' responses were compared against their OSCE performance. RESULTS: Of the 116 students who sat for both formative OSCEs, 82.8% (n=96) and 86.2% (n=100) responded to the first and second survey respectively. Most students were comfortable to receive feedback (91.3% in FTF, 96% in EW) with EW feedback associated with higher comfort levels (p=0.022). Distress affected a small number with no differences between either method (13.5% in FTF, 10% in EW, p=0.316). Most students perceived both types of feedback improved their performance (89.6% in FTF, 95% in EW); this perception was significantly stronger for EW feedback (p=0.008). Students who preferred EW feedback had lower OSCE scores compared to those preferring FTF feedback (mean scores ± SD: 43.8 ± 5.3 in EW, 47.2 ± 6.5 in FTF, p=0.049). Students ranked the "marking rubric" to be the most valuable aspect of the EW feedback. Tutors felt both methods of feedback were equally beneficial. Few examiners felt they needed training (21.4% in FTF, 15% in EW) but students perceived this need for tutors' training differently (53.1% in FTF, 46% in EW) CONCLUSION: Whilst both methods of OSCE feedback were highly valued, students preferred to receive EW feedback and felt it was more beneficial. Learning cultures of Malaysian students may have influenced this view. Information provided in EW feedback should be tailored accordingly to provide meaningful feedback in OSCE exams.

High sensitivity Ge-on-Si single-photon avalanche diode detectors.

The performance of planar geometry Ge-on-Si single-photon avalanche diode detectors of 26µm diameter is presented. Record low dark count rates are observed, remaining less than 100 K counts per second at 6.6% excess bias and 125 K. Single-photon detection efficiencies are found to be up to 29.4%, and are shown to be temperature insensitive. These performance characteristics lead to a significantly reduced noise equivalent power (NEP) of 7.7×10-17WHz-12 compared to prior planar devices, and represent a two orders of magnitude reduction in NEP compared to previous Ge-on-Si mesa devices of a comparable diameter. Low jitter values of 134±10ps are demonstrated.

A Framework for Equity Access to Primary Dental Care.

The objective of this study was to demonstrate face validity with a novel resource allocation framework designed to maximize equity into dental booking systems. The study was carried out in 2014. Eleven experts in primary dental care practice in Southern Brazil participated, using a three-round consensus group technique. First, the experts reached consensus on the items to be included in a 5-level diagnostic scale. They identified 21 clinical conditions and categorized them according to the oral health intervention required. Then, they described workload and activity standards for dental staff to carry out health promotion, oral disease prevention, dental treatment, dental rehabilitation, and urgent dental care. Finally, they agreed upon a set of wait times for primary dental care, establishing maximum waits from 2 to 365 days, according to the diagnostic classification. The framework demonstrated potential ability to promote more equitable access to primary dental services, since equal diagnostic classifications share the same waiting times for the dental care they require.

Characterization of integrated waveguides by atomic-force-microscopy-assisted mid-infrared imaging and spectroscopy.

A novel spectroscopy technique to enable the rapid characterization of discrete mid-infrared integrated photonic waveguides is demonstrated. The technique utilizes lithography patterned polymer blocks that absorb light strongly within the molecular fingerprint region. These act as integrated waveguide detectors when combined with an atomic force microscope that measures the photothermal expansion when infrared light is guided to the block. As a proof of concept, the technique is used to experimentally characterize propagation loss and grating coupler response of Ge-on-Si waveguides at wavelengths from 6 to 10 µm. In addition, when the microscope is operated in scanning mode at fixed wavelength, the guided mode exiting the output facet is imaged with a lateral resolution better than 500 nm i.e. below the diffraction limit. The characterization technique can be applied to any mid-infrared waveguide platform and can provide non-destructive in-situ testing of discrete waveguide components.

Terahertz absorption-saturation and emission from electron-doped germanium quantum wells.

We study radiative relaxation at terahertz frequencies in n-type Ge/SiGe quantum wells, optically pumped with a terahertz free electron laser. Two wells coupled through a tunneling barrier are designed to operate as a three-level laser system with non-equilibrium population generated by optical pumping around the 1→3 intersubband transition at 10 THz. The non-equilibrium subband population dynamics are studied by absorption-saturation measurements and compared to a numerical model. In the emission spectroscopy experiment, we observed a photoluminescence peak at 4 THz, which can be attributed to the 3→2 intersubband transition with possible contribution from the 2→1 intersubband transition. These results represent a step towards silicon-based integrated terahertz emitters.

Ge-on-Si waveguides for sensing in the molecular fingerprint regime.

Low loss, single mode, Ge-on-Si rib waveguides are used to demonstrated optical sensing in the molecular fingerprint region of the mid-infrared spectrum. Sensing is carried out using two spin-coated films, with strong absorption in the mid-infrared. These films are used to calibrate the modal overlap with an analyte, and therefore experimentally demonstrate the potential for Ge-on-Si waveguides for mid-infrared sensing applications. The results are compared to Fourier transform infrared spectroscopy measurements. The advantage of waveguide spectroscopy is demonstrated in terms of the increased optical interaction, and a new multi-path length approach is demonstrated to improve the dynamic range, which is not possible with conventional FTIR or attenuated total reflection (ATR) measurements. These results highlight the potential for Ge-on-Si as an integrated sensing platform for healthcare, pollution monitoring and defence applications.

3D LIDAR imaging using Ge-on-Si single-photon avalanche diode detectors.

We present a scanning light detection and ranging (LIDAR) system incorporating an individual Ge-on-Si single-photon avalanche diode (SPAD) detector for depth and intensity imaging in the short-wavelength infrared region. The time-correlated single-photon counting technique was used to determine the return photon time-of-flight for target depth information. In laboratory demonstrations, depth and intensity reconstructions were made of targets at short range, using advanced image processing algorithms tailored for the analysis of single-photon time-of-flight data. These laboratory measurements were used to predict the performance of the single-photon LIDAR system at longer ranges, providing estimations that sub-milliwatt average power levels would be required for kilometer range depth measurements.

1.4 million Q factor Si3N4 micro-ring resonator at 780 nm wavelength for chip-scale atomic systems.

A silicon nitride micro-ring resonator with a loaded Q factor of 1.4 × 106 at 780 nm wavelength is demonstrated on silicon substrates. This is due to the low propagation loss waveguides achieved by optimization of waveguide sidewall interactions and top cladding refractive index. Potential applications include laser frequency stabilization allowing for chip-scale atomic systems targeting the 87Rb atomic transition at 780.24 nm. The temperature dependent wavelength shift of the micro-ring was determined to be 13.1 pm/K indicating that a minimum temperature stability of less than ±15 mK is required for such devices for wavelength locking applications. If a polyurethane acrylate top cladding of an optimized thickness is used then the micro-ring could effectively be athermal, resulting in reduced footprint, power consumption, and cost of potential devices.