Cooling a mechanical resonator mode to a sub-thermal state has been a long-standing challenge in physics. This pursuit has recently found traction in the field of optomechanics in which a mechanical ...mode is coupled to an optical cavity. An alternate method is to couple the resonator to a well-controlled two-level system. Here we propose a protocol to dissipatively cool a room temperature mechanical resonator using a nitrogen-vacancy centre ensemble. The spin ensemble is coupled to the resonator through its orbitally-averaged excited state, which has a spin-strain interaction that has not been previously studied. We experimentally demonstrate that the spin-strain coupling in the excited state is 13.5±0.5 times stronger than the ground state spin-strain coupling. We then theoretically show that this interaction, combined with a high-density spin ensemble, enables the cooling of a mechanical resonator from room temperature to a fraction of its thermal phonon occupancy.
This paper presents a merged-two-stage circuit topology suitable for either wide-range dc input voltage or ac line voltage at low-to-moderate power levels (e.g., up to 30 W). This two-stage topology ...is based on a soft-charged switched-capacitor preregulator/transformation stage and a high-frequency magnetic regulator stage. Soft charging of the switched capacitor circuit, zero voltage switching of the high-frequency regulator circuit, and time-based indirect current control are used to maintain high efficiency, high power density, and high power factor. The proposed architecture is applied to an LED driver circuit, and two implementations are demonstrated: a wide input voltage range dc-dc converter and a line interfaced ac-dc converter. The dc-dc converter shows 88%-96% efficiency at 30-W power across 25-200-V input voltage range, and the ac-dc converter achieves 88% efficiency with 0.93 power factor at 8.4-W average power. Contributions of this paper include: 1) demonstrating the value of a merged two-stage architecture to provide substantial design benefits in high-input voltage, low-power step down conversion applications, including both wide-range-input dc-dc and line-input ac-dc systems; 2) introduction of a multimode soft-charged SC stage for the merged architecture that enables compression of an 8:1 input voltage range into a 2:1 intermediate range, along with its implementation, loss considerations, and driving methods; and 3) merging of this topology with an resonant transition discontinuous-mode inverted buck stage and pseudocurrent control to enable step-down power conversion (e.g., for LED lighting) operating at greatly increased frequencies and reduced magnetics size than with more conventional approaches.
Spectrometry is widely used for the characterization of materials, tissues, and gases, and the need for size and cost scaling is driving the development of mini and microspectrometers. While ...nanophotonic devices provide narrowband filtering that can be used for spectrometry, their practical application has been hampered by the difficulty of integrating tuning and read-out structures. Here, a nano-opto-electro-mechanical system is presented where the three functionalities of transduction, actuation, and detection are integrated, resulting in a high-resolution spectrometer with a micrometer-scale footprint. The system consists of an electromechanically tunable double-membrane photonic crystal cavity with an integrated quantum dot photodiode. Using this structure, we demonstrate a resonance modulation spectroscopy technique that provides subpicometer wavelength resolution. We show its application in the measurement of narrow gas absorption lines and in the interrogation of fiber Bragg gratings. We also explore its operation as displacement-to-photocurrent transducer, demonstrating optomechanical displacement sensing with integrated photocurrent read-out.
Live interactive teledermatology compared to in‐person care – a systematic review Andrees, V.; Klein, T.M.; Augustin, M. ...
JEADV. Journal of the European Academy of Dermatology and Venereology/Journal of the European Academy of Dermatology and Venereology,
April 2020, 2020-Apr, 2020-04-00, 20200401, Letnik:
34, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Teledermatology is a rapidly developing field of dermatological care, giving the opportunity to deliver more efficient healthcare to patients in remote areas. Live interactive (LI) teledermatology ...uses videoconferencing and, hence, allows for direct communication. A current overview on effectiveness, costs, feasibility and accuracy of LI applications compared to standard care is missing. The present systematic review provides this overview on LI teledermatology. Two databases were searched until April 2019, followed by title, and full‐text screening. Additionally, reference lists of the detected eligible articles were screened for further eligible studies. Studies comparing LI applications with standard care were included. Data on study design, sample size, country, objectives, main findings and characteristics of LI applications were extracted. Results on time effectiveness, costs, accuracy and feasibility of LI applications were synthesized. Additionally, the quality of included studies was assessed. Twenty‐three publications were included in the final analysis: seventeen case–control studies and six randomized controlled trials. Included studies were published between 1997 and 2017. Study quality differed across studies. The studies were carried out in eight different countries. Eleven studies focused on patient consultation, three on patient organization and nine on combined applications of the aforementioned. Nine studies investigated applications facilitating patient–provider interaction. Fourteen studies evaluated applications combining patient–provider and provider–provider interaction, meaning the patient sits next to one provider while using LI applications to interact with another provider. This review reveals that LI applications can be a time effective substitute of or supplement to standard dermatological care. Results demonstrated that LI and standard care are comparable with regard to feasibility and accuracy. No clear tendencies can be reported with regard to costs. However, there is a lack of current comparative studies.
Linked Commentary: G. Burg. J Eur Acad Dermatol Venereol 2020; 34: 670–671. https://doi.org/10.1111/jdv.16318.
Automated diffraction tomography (ADT) allows the collection of three-dimensional (3d) diffraction data sets from crystals down to a size of only few nanometres. Imaging is done in STEM mode, and ...diffraction data are collected with quasi-parallel beam nanoelectron diffraction (NED). Here, we present a set of developed processing steps necessary for automatic unit-cell parameter determination from the collected 3d diffraction data. Cell parameter determination is done via extraction of peak positions from a recorded data set (called the data reduction path) followed by subsequent cluster analysis of difference vectors. The procedure of lattice parameter determination is presented in detail for a beam-sensitive organic material. Independently, we demonstrate a potential (called the full integration path) based on 3d reconstruction of the reciprocal space visualising special structural features of materials such as partial disorder. Furthermore, we describe new features implemented into the acquisition part.
Essentials
The value of compression therapy in acute phase of deep vein thrombosis is still unclear.
Patients with deep vein thrombosis received acute compression hosiery, bandaging, or none.
Acute ...compression reduces irreversible skin signs related to post thrombotic syndrome.
Compression hosiery may be the preferred choice for the acute phase
Summary
Background
The effectiveness of compression therapy in the acute phase of deep vein thrombosis (DVT) is not yet determined.
Objectives
To investigate the impact of compression therapy in the acute phase of DVT on determinants of the Villalta score, health‐related quality of life (HRQOL), and costs.
Patients/Methods
Eight hundred and sixty‐five patients with proximal DVT (substudy of the IDEAL DVT study) received, immediately after DVT diagnosis, either no compression, multilayer bandaging, or hosiery. In the acute phase and 3 months after diagnosis, HRQOL was determined by use of the EQ‐5D, SF6D, and VEINES‐QoL intrinsic method (VEINES‐QoLint). At 3 months, signs and symptoms were assessed for the total and separate items of the Villalta score, and healthcare costs were calculated.
Results
The compression groups had lower overall objective Villalta scores than the no‐compression group (1.47 standard deviation (SD) 1.570 and 1.59 SD 1.64 versus 2.21 SD 2.15). The differences were mainly attributable to irreversible skin signs (induration, hyperpigmentation, and venectasia) and pain on calf compression. Subjective and total Villalta scores were similar across groups. Differences in HRQOL were only observed at 1 month; HRQOL was better for hosiery (EQ‐5D 0.86 SD 0.18; VEINES‐QoLint 0.66 SD 0.18) than for multilayer compression bandaging (EQ‐5D 0.81 SD 0.23; VEINES‐QoLint 0.62 SD 0.19). Mean healthcare costs per patient were €417.08 (€354.10 to €489.30) for bandaging, €114.25 (€92.50 to €198.43) for hosiery, and €105.86 (€34.63 to €199.30) for no compression.
Conclusions
Initial compression reduces irreversible skin signs, edema, and pain on calf compression. Multilayer bandaging is slightly more effective than hosiery, but has substantially higher costs, without a gain in HRQOL. From a patient and economic perspective, compression hosiery would be preferred when initial compression is applied. Trial registration: IDEAL DVT study ClinicalTrials.gov number, NCT01429714.
The ultimate aim of electron diffraction data collection for structure analysis is to sample the reciprocal space as accurately as possible to obtain a high-quality data set for crystal structure ...determination. Besides a more precise lattice parameter determination, fine sampling is expected to deliver superior data on reflection intensities, which is crucial for subsequent structure analysis. Traditionally, three-dimensional (3D) diffraction data are collected by manually tilting a crystal around a selected crystallographic axis and recording a set of diffraction patterns (a tilt series) at various crystallographic zones. In a second step, diffraction data from these zones are combined into a 3D data set and analyzed to yield the desired structure information. Data collection can also be performed automatically, with the recent advances in tomography acquisition providing a suitable basis. An experimental software module has been developed for the Tecnai microscope for such an automated diffraction pattern collection while tilting around the goniometer axis. The module combines STEM imaging with diffraction pattern acquisition in nanodiffraction mode. It allows automated recording of diffraction tilt series from nanoparticles with a size down to 5
nm.
Lasing in metallic-coated nanocavities Hill, Martin T; Oei, Yok-Siang; Smalbrugge, Barry ...
Nature photonics,
10/2007, Letnik:
1, Številka:
10
Journal Article
Recenzirano
Metallic cavities can confine light to volumes with dimensions considerably smaller than the wavelength of light. It is commonly believed, however, that the high losses in metals are prohibitive for ...laser operation in small metallic cavities. Here we report for the first time laser operation in an electrically pumped metallic-coated nanocavity formed by a semiconductor heterostructure encapsulated in a thin gold film. The demonstrated lasers show a low threshold current and their dimensions are smaller than the smallest electrically pumped lasers reported so far. With dimensions comparable to state-of-the-art electronic transistors and operating at low power and high speed, they are a strong contender as basic elements in digital photonic very large-scale integration. Furthermore we demonstrate that metallic-coated nanocavities with modal volumes smaller than dielectric cavities can have moderate quality factors.
Random dielectrics defines a class of non‐absorbing materials where the index of refraction is randomly arranged in space. Whenever the transport mean free path is sufficiently small, light can be ...confined in modes with very small volume. Random photonic modes have been investigated for their basic physical insights, such as Anderson localization, and recently several applications have been envisioned in the field of renewable energies, telecommunications, and quantum electrodynamics. An advantage for optoelectronics and quantum source integration offered by random systems is their high density of photonic modes, which span a large range of spectral resonances and spatial distributions, thus increasing the probability to match randomly distributed emitters. Conversely, the main disadvantage is the lack of deterministic engineering of one or more of the many random photonic modes achieved. This issue is solved by demonstrating the capability to electrically and mechanically control the random modes at telecom wavelengths in a 2D double membrane system. Very large and reversible mode tuning (up to 50 nm), both toward shorter or longer wavelength, is obtained for random modes with modal volumes of the order of few tens of (λ/n)3.
A disordered dielectric device with embedded quantum dots, which allows a fine, reversible, and large tuning of small‐volume localized random modes with mechanical and electric techniques, is presented. Mode control is illustrated with numerical simulations and experimentally observed with near‐field and standard microscopy methods. The large spectral tuning with mode steadiness makes such devices suitable for optoelectronics and quantum cavity electrodynamics applications.
Favourable outcomes of breast cancer screening trials in the 1970s and 1980s resulted in the launch of population-based service screening programmes in many Western countries. We investigated whether ...improvements in mammography and treatment modalities have had an influence on the effectiveness of breast cancer screening from 1975 to 2008.
In Nijmegen, the Netherlands, 55,529 women received an invitation for screening between 1975 and 2008. We designed a case-referent study to evaluate the impact of mammographic screening on breast cancer mortality over time from 1975 to 2008. A total number of 282 breast cancer deaths were identified, and 1410 referents aged 50-69 were sampled from the population invited for screening. We estimated the effectiveness by calculating the odds ratio (OR) indicating the breast cancer death rate for screened vs unscreened women.
The breast cancer death rate in the screened group over the complete period was 35% lower than in the unscreened group (OR=0.65; 95% CI=0.49-0.87). Analysis by calendar year showed an increasing effectiveness from a 28% reduction in breast cancer mortality in the period 1975-1991 (OR=0.72; 95% CI=0.47-1.09) to 65% in the period 1992-2008 (OR=0.35; 95% CI=0.19-0.64).
Our results show an increasingly strong reduction in breast cancer mortality over time because of mammographic screening.
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