Coherent Dynamics in Quantum Emitters under Dichromatic Excitation.

We characterize the coherent dynamics of a two-level quantum emitter driven by a pair of symmetrically detuned phase-locked pulses. The promise of dichromatic excitation is to spectrally isolate the excitation laser from the quantum emission, enabling background-free photon extraction from the emitter. While excitation is not possible without spectral overlap between the exciting pulse and the quantum emitter transition for ideal two-level systems due to cancellation of the accumulated pulse area, we find that any additional interactions that interfere with cancellation of the accumulated pulse area may lead to a finite stationary population inversion. Our spectroscopic results of a solid-state two-level system show that, while coupling to lattice vibrations helps to improve the inversion efficiency up to 50% under symmetric driving, coherent population control and a larger amount of inversion are possible using asymmetric dichromatic excitation, which we achieve by adjusting the ratio of the intensities between the red- and blue-detuned pulses. Our measured results, supported by simulations using a real-time path-integral method, offer a new perspective toward realizing efficient, background-free photon generation and extraction.

[Incidence of unintended pregnancy within 2 years after delivery and its influencing factors in China].

Objective: To investigate the present situation of unintended pregnancy within two years postpartum and its influencing factors in China. Methods: Participants who delivered a live birth at 60 hospitals in 15 provinces in the eastern, central and western regions of China during July 2015 to June 2016 were interviewed by using structured questionnaire. Information on occurrence of unintended pregnancy within 2 years after delivery, postpartum contraceptive use, sexual resumption, breastfeeding, and women's socio-demographic characteristics, and so on, were collected. Life-table analysis, cluster log-rank tests and a 2-level Cox regression model were used for data analysis. Results: A total of 18 045 postpartum women were investigated. The cumulative 1- and 2-year unintended pregnancy rates after delivery were 5.3% (95%CI: 4.5%－6.1%) and 13.1% (95%CI: 11.3%－14.8%), respectively. Cox regression model analysis showed that the risk of unintended pregnancy within 2 years postpartum were increased in younger women, ethnic minorities, women with abortion history, and those who had a vaginal delivery with short lactation time and late postpartum contraceptive initiation (all P<0.01). The risk of postpartum unintended pregnancy was not associated with geographic regions and hospitals where women gave a birth (all P>0.05). Conclusions: In China, the risk of unintended pregnancy within 2 years after delivery is relatively high. Service institutions and service providers should improve the quality of postpartum family planning services, promote the use of high effect contraceptive methods, and educate women to use a method at the time of their sexual resumption or even before.

Fundamental Limits to Coherent Photon Generation with Solid-State Atomlike Transitions.

Coherent generation of indistinguishable single photons is crucial for many quantum communication and processing protocols. Solid-state realizations of two-level atomic transitions or three-level spin-Λ systems offer significant advantages over their atomic counterparts for this purpose, albeit decoherence can arise due to environmental couplings. One popular approach to mitigate dephasing is to operate in the weak-excitation limit, where the excited-state population is minimal and coherently scattered photons dominate over incoherent emission. Here we probe the coherence of photons produced using two-level and spin-Λ solid-state systems. We observe that the coupling of the atomiclike transitions to the vibronic transitions of the crystal lattice is independent of the driving strength, even for detuned excitation using the spin-Λ configuration. We apply a polaron master equation to capture the non-Markovian dynamics of the vibrational manifolds. These results provide insight into the fundamental limitations to photon coherence from solid-state quantum emitters.

Screening Nuclear Field Fluctuations in Quantum Dots for Indistinguishable Photon Generation.

A semiconductor quantum dot can generate highly coherent and indistinguishable single photons. However, intrinsic semiconductor dephasing mechanisms can reduce the visibility of two-photon interference. For an electron in a quantum dot, a fundamental dephasing process is the hyperfine interaction with the nuclear spin bath. Here, we directly probe the consequence of the fluctuating nuclear spins on the elastic and inelastic scattered photon spectra from a resident electron in a single dot. We find the in-plane component of the nuclear Overhauser field leads to detuned Raman scattered photons, broadened over experimental time scales by field fluctuations, which are distinguishable from both the elastic and incoherent components of the resonance fluorescence. This significantly reduces two-photon interference visibility. However, we demonstrate successful screening of the nuclear spin noise, which enables the generation of coherent single photons that exhibit high visibility two-photon interference.

Anomalous diamagnetic shifts in InP-GaP lateral quantum-wires.

Linearly polarized photoluminescence (PL) measurements were carried out on InP-GaP lateral nanowires grown using a lateral composition modulation method in pulsed magnetic fields up to ∼ 50 T. In these structures, the energy band alignment becomes type-I and type-II in In-rich wire and Ga-rich barrier regions, respectively. It is revealed that the polarization of the type-I PL is oriented along the [11̄0] crystal direction, whereas that of the type-II PL is along the [110] direction in the absence of magnetic field. These two different PL peaks exhibit anomalous energy shifts with respect to the direction of the magnetic field due to the variation of the confined energy in the exciton center of mass potential.

Near-unity coupling efficiency of a quantum emitter to a photonic crystal waveguide.

A quantum emitter efficiently coupled to a nanophotonic waveguide constitutes a promising system for the realization of single-photon transistors, quantum-logic gates based on giant single-photon nonlinearities, and high bit-rate deterministic single-photon sources. The key figure of merit for such devices is the ß factor, which is the probability for an emitted single photon to be channeled into a desired waveguide mode. We report on the experimental achievement of ß=98.43%±0.04% for a quantum dot coupled to a photonic crystal waveguide, corresponding to a single-emitter cooperativity of η=62.7±1.5. This constitutes a nearly ideal photon-matter interface where the quantum dot acts effectively as a 1D "artificial" atom, since it interacts almost exclusively with just a single propagating optical mode. The ß factor is found to be remarkably robust to variations in position and emission wavelength of the quantum dots. Our work demonstrates the extraordinary potential of photonic crystal waveguides for highly efficient single-photon generation and on-chip photon-photon interaction.

Effect of growth temperature and quantum structure on InAs/GaAs quantum dot solar cell.

InGaAs-capped InAs quantum dots (QDs) and InAs QDs were adopted for the study of the effects through growth temperature and the band structure of InAs QDs on the performance of GaAs-based QD solar cell. It has been shown that the defects due to low temperature growth resulted in the decrease of Voc, Jsc and external quantum efficiency for GaAs bulk solar cell and QD embedded solar cells. It has been also found that InAs QDs act as defects by trapping photo-generated carries which affect the carrier transport in QD solar cell. The QD solar cell with InGaAs-capped InAs QDs showed higher performance than the QD solar cell with only InAs QDs. Such result has been explained by photo-generated carrier trapping and tunneling through InGaAs QW state in InGaAs-capped InAs QDs.

Fabrication of GaAs/Al0.3Ga0.7As multiple quantum well nanostructures on (100) si substrate using a 1-nm InAs relief layer.

Nanometer scale thin InAs layer has been incorporated between Si (100) substrate and GaAs/Al0.3Ga0.7As multiple quantum well (MQW) nanostructure in order to reduce the defects generation during the growth of GaAs buffer layer on Si substrate. Observations based on atomic force microscopy (AFM) and transmission electron microscopy (TEM) suggest that initiation and propagation of defect at the Si/GaAs interface could be suppressed by incorporating thin (1 nm in thickness) InAs layer. Consequently, the microstructure and resulting optical properties improved as compared to the MQW structure formed directly on Si substrate without the InAs layer. It was also observed that there exists some limit to the desirable thickness of the InAs layer since the MQW structure having thicker InAs layer (4 nm-thick) showed deteriorated properties.

Effects of growth parameters on the structural and optical properties of InP/InGaP quantum structures for 808-nm-wavelength emissions.

InP/InGaP quantum structures with 808-nm-wavelength emissions were grown on semi-insulating GaAs (100) substrates via migration-enhanced molecular beam epitaxy. The effects of the growth conditions on the structural and optical properties of the InP/InGaP quantum structures were investigated. The scanning electron microscopy and atomic force microscopy images showed that the two-dimensional InP/InGaP quantum structures were transited to one-dimensional structures with an increasing repetition cycle. The photoluminescence spectra showed that the optical properties of the InP/InGaP quantum structures were significantly affected by various migration-enhanced epitaxy repetition numbers and growth temperatures. These results can help improve understanding of the effects of growth parameters on the structural and optical properties of InP/InGaP quantum structures for 808-nm-wavelength emissions.

Self-assembled growth of GaAs anti quantum dots in InAs matrix by migration enhanced molecular beam epitaxy.

Self-assembled GaAs anti quantum dots (AQDs) were grown in an InAs matrix via migration enhanced molecular beam epitaxy. The transmission electron microscopy image showed that the 2D to 3D transition thickness is below 1.5 monolayers (MLs) of GaAs coverage. The average diameter and height of the GaAs AQDs for 1.5 ML GaAs coverage taken from the atomic force microscopy image were approximately 29.0 nm and 1.4 nm, respectively. The density was approximately 6.0 x 10(10) cm(-2). The size of the AQDs was enlarged in the InAs matrix compared with that on the surface. These results indicate that the GaAs AQDs in the InAs matrix under tensile strain can be effectively formed with the assistance of the migration enhanced epitaxy method.

Early outcomes with robot-assisted vs. minimally invasive esophagectomy for esophageal cancer: a systematic review and meta-analysis of matched studies.

OBJECTIVE: The current study aimed to compare intraoperative and early postoperative outcomes with robot-assisted esophagectomy (RAE) vs. minimally invasive esophagectomy (MIE) for esophageal cancer. MATERIALS AND METHODS: We searched PubMed, Embase, and Google Scholar for randomized controlled trials (RCTs) or propensity-matched cohort studies comparing RAE with MIE for patients with esophageal cancer. RESULTS: One RCT and 14 retrospective propensity-matched studies were included. Meta-analysis revealed significantly increased operative time (MD: 32.89 95% CI: 6.42, 59.35 I2=95% p=0.01) and reduced blood loss (MD: -35.15 95% CI: -61.30, -8.99 I2=82% p=0.008) with RAE. Both the results turned statistically non-significant on exclusion of one study. The was no difference between the two techniques for anastomotic leak (RR: 0.98 95% CI: 0.76, 1.24 I2=0% p=0.84), chyle leak (RR: 0.94 95% CI: 0.48, 1.83 I2=0% p=0.86), recurrent laryngeal nerve palsy (RR: 0.92 95% CI: 0.61, 1.39 I2=70% p=0.69), cardiac complication (RR: 1.06 95% CI: 0.64, 1.78 I2=0% p=0.82), infectious complications (RR: 1.06 95% CI: 0.47, 2.42 I2=0% p=0.88), conversion to open surgery (RR: 0.60 95% CI: 0.25, 1.43 I2=56% p=0.25) or early mortality (RR: 1.04 95% CI: 0.74, 1.47 I2=0% p=0.82). However, pulmonary complications were significantly reduced with RAE as compared to MIE (RR: 0.72 95% CI: 0.60, 0.86 I2=0% p=0.003). CONCLUSIONS: RAE is associated with a tendency of longer operating time and reduced blood loss as compared to MIE. RAE significantly reduces pulmonary complications as compared to MIE but has no impact on the incidence of anastomotic leak, chyle leak, RLN palsy, cardiac complication, infectious complications, conversion to open surgery, or early mortality.

Intrinsically p-type cuprous iodide semiconductor for hybrid light-emitting diodes.

Cuprous halides, characterized by a direct wide band-gap and a good lattice matching with Si, is an intrinsic p-type I-VII compound semiconductor. It shows remarkable optoelectronic properties, including a large exciton binding energy at room temperature and a very small piezoelectric coefficient. The major obstacle to its application is the difficulty in growing a single-crystal epitaxial film of cuprous halides. We first demonstrate the single crystal epitaxy of high quality cuprous iodide (CuI) film grown on Si and sapphire substrates by molecular beam epitaxy. Enhanced photoluminescence on the order of magnitude larger than that of GaN and continuous-wave optically pumped lasing were found in MBE grown CuI film. The intrinsic p-type characteristics of CuI were confirmed using an n-AlGaN/p-CuI junction that emits blue light. The discovery will provide an alternative way towards highly efficient optoelectronic devices compatible with both Si and III-nitride technologies.

Insights Into the Evolution of Chemoreceptor Genes Superfamily in Tyrophagus putrescentiae (Acari: Acaridae).

All living organisms, including animals, plants, fungi, and bacteria, use the olfactory system to recognize chemicals or pheromone from their environment. Insects detect a volatile substance using odorant receptors (ORs) or gustatory receptors (GRs) and ionotropic receptors (IRs). The gene families of the olfactory system in Acari are still not clear. In this study, we identified seven ORs, one GR, and five IRs from the transcriptome of the storage mite, Tyrophagus putrescentiae Schrank. No olfactory coreceptor was found in this transcriptome. Phylogenetic analysis of these gene families with other Arthropoda species revealed the conservation of carbon dioxide receptors in all tested flying insects and T. putrescentiae Most of these ORs and GRs were unique to three mosquitoes (Anopheles gambiae Giles, Culex quinquefasciatus Say, and Aedes aegypti L.), Ixodes scapularis Say and Pediculus humanus L., indicating their involvement in specific aspects of both gustatory and olfactory perception. Some clades contained receptors obtained from all tested insect vector species, indicating a degree of conservation among some vector-dependent OR lineages. IRs family was a highly dynamic and independent original of the chemoreceptor genes subfamily. Our findings would make it possible for future research on the chemosensory recognition mechanism in Acari.

Thermal conductivity of the diamond-chain compound Cu3(CO3)2(OH)2.

Thermal conductivity (κ) of a distorted spin diamond-chain system, Cu3(CO3)2(OH)2, is studied at low temperatures down to 0.3 K and in magnetic fields up to 14 T. In zero field, the κ(T) curve with heat current along the chain direction has very small magnitudes and shows a pronounced three-peak structure. The magnetic fields along and perpendicular to the chains change the κ strongly in a way having good correspondence to the changes of magnetic specific heat in fields. The data analysis based on the Debye model for phononic thermal conductivity indicates that the heat transport is due to phonons and the three-peak structure is caused by two resonant scattering processes by the magnetic excitations. In particular, the spin excitations of the chain subsystem are strongly scattering phonons rather than transporting heat.

Temperature-Dependent Development and Reproductive Traits of Tyrophagus putrescentiae (Sarcoptiformes: Acaridae) Reared on Different Edible Mushrooms.

China is the largest producer, consumer, and exporter of mushrooms in the world. The storage mite, Tyrophagus putrescentiae Schrank, is one of the most important arthropod pests in mushroom cultivation. This study investigated the development and reproductive traits of this mite reared on four mushroom species: Agaricus bisporus Lange, Pleurotus ostreatus Kumm, Auricularia polytricha (Mont.) Sacc., and Flammulina velutipes (Fr.) Sing., at seven constant temperatures ranging from 16 to 34 °C at 80% relative humidity. Development time for the immature stages decreased with increasing temperature, and was also significantly affected by mushroom species. The shortest immature developmental period (7.0 ± 0.2 d) was observed at 31 °C when reared on F. velutipes, while the longest development was at 16 °C (36.0 ± 0.3 d) reared on P. ostreatus. The effects of temperature and mushroom hosts on the development, female longevity, and reproduction were also significant. The lower threshold temperatures from egg-to-adult for the four mushroom species were 11.97, 12.02, 10.80, and 11.57 °C, for A. bisporus, P. ostreatus, Au. polytricha, and F. velutipes, and the thermal constants were 133.3, 136.8, 165.2, and 135.9 degree days (°C d), for the same mushroom species, respectively. Life table parameters at 25 °C were estimated as follows: net reproductive rates (R0), 59.16, 28.94, 42.62, and 62.93, and intrinsic rate of natural increase (rm), 0.24, 0.13, 0.17, and 0.24, respectively. These results suggest that these mushrooms are suitable hosts for T. putrescentiae, and the storage mite may be able to adapt to higher temperatures.

Single-photon non-linear optics with a quantum dot in a waveguide.

Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.

The expression of glucose regulated protein-94 in colorectal carcinoma cells treated by sodium butyrate.

The expression of glucose regulated protein 94 (GRP94) during the treatment of human colorectal carcinoma cell line-Clone A cells with sodium butyrate was studied. Sodium butyrate (SB) can cause functional and morphological effects on Clone A cells including growth arrest at G0/G1 stage and cell differentiation as observed by morphological changes, MTT and flow cytometry assays, as well as reduced Grp94 gene expression as shown by Northern blot and Western blot assays. The possible mechanism of the correlation between Grp94 gene expression and tumor growth inhibition and cell differentiation is briefly discussed.

Determination of ß-glucuronidase in human colorectal carcinoma cell lines.

AIM: To study the relationship between ß-glucuronidase and the invasiveness of human colorectal carcinoma cell lines. METHODS: Six colorectal carcinoma cell lines, including three well-differentiated (CX1, CCL187, and CCL229) and three poorly differentiated ones (CCL227, CCL228, and Clone A), were analyzed by Fischman's method to determine the concentration of ß-glucuronidase in the medium. RESULTS: Low levels of ß-glucuronidase (activity range: 1.29 to 1.96 µg/106 cells·h) were associated with poor invasiveness. This finding was in contrast to the elevated levels of the enzyme (2.46-3.37 µg/106·h) detected in the medium derived from the more aggressively invasive cells (CCL 227, CCL 228, Clone A, and CCL 229). CONCLUSION: Highly invasive colorectal carcinoma cells secreted higher levels of ß-glucuronidase than the poorly invasive cells. Determination of secreted ß-glucuronidase might represent a useful in vitro measurement tool to assess the invasiveness of colorectal carcinoma.

Differential expression of a novel colorectal cancer differentiation-related gene in colorectal cancer.

AIM: To investigate SBA2 expression in CRC cell lines and surgical specimens of CRC and autologous healthy mucosa. METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) was used for relative quantification of SBA2 mRNA levels in 4 human CRC cell lines with different grades of differentiation and 30 clinical samples. Normalization of the results was achieved by simultaneous amplification of beta-actin as an internal control. RESULTS: In the exponential range of amplification, fairly good linearity demonstrated identical amplification efficiency for SBA2 and beta-actin (82%). Markedly lower levels of SBA2 mRNA were detectable in tumors, as compared with the coupled normal counterparts P<0.01). SBA2 expression was significantly (0.01>P < 0.05) correlated with the grade of differentiation in CRC, with relatively higher levels in well-differentiated samples and lower in poorly-differentiated cases. Of the 9 cases with lymph nodes affected, 78% (7/9) had reduced SBA2 mRNA expression in contrast to 24% (5/21) in non-metastasis samples 0.01>P<0.05). CONCLUSION: SBA2 gene might be a promising novel biomarker of cell differentiation in colorectal cancer and its biological features need further studies.