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The first highly enantioselective asymmetric decarboxylative addition of β-keto acids with 3-alkenyl-oxindoles bearing an all-carbon quaternary stereocenter have been developed. The relevant products were acquired in 49-98% yields with 88-98% enantioselectivities in the presence of 0.04-1.0 mol % of chiral rhodium catalyst. The comprehensive practicability of this method was proven in the preparation of the key intermediate, which can be easily transformed into analogues of physovenine and physostigmine.

A highly enantioselective conjugate addition of indolizine and its analogues with α,β-unsaturated 2-acyl imidazoles has been developed.

Direct catalytic asymmetric vinylogous Michael addition to construct an acyclic all-carbon quaternary center with novel 3-alkenyl-oxindoles.

Developing innovative dynamic kinetic resolution (DKR) modes and achieving the highly regio- and enantioselective semihydrogenation of unsymmetrical α-diketones are two formidable challenges in the field of contemporary asymmetric (transfer) hydrogenation. In this work, we report the highly regio- and stereoselective asymmetric semi-transfer hydrogenation of unsymmetrical α-diketones through a unique DKR mode, which features the reduction of the carbonyl group distal from the labile stereocenter, while the proximal carbonyl remains untouched. Moreover, the protocol affords a variety of enantioenriched acyclic ketones with α-hydroxy-α′-C(sp2)-functional groups, which represent a new product class that has not been furnished in known arts. The utilities of the products have been demonstrated in a series of further transformations including the rapid synthesis of drug molecules. Density functional theory calculations and plenty of control experiments have also been conducted to gain more mechanistic insights into the highly selective semihydrogenation. Nasl. z nasl. zaslona. Opis vira z dne 4. 1. 2023. Bibliografija: str. 596-598. Abstract. National Natural Science Foundation of China National Natural Science Foundation of China National Natural Science Foundation of China Research Program of the Chinese Academy of Sciences Fujian Natural Science Foundation ARRS ARRS

An enantioselective cyclopropanation reaction of sulfoxonium ylides with β,γ-unsaturated ketoesters catalyzed by a chiral rhodium catalyst has been realized. A variety of optically pure 1,2,3-trisubstituted cyclopropanes was synthesized in 48-89% yields, with up to 99% ee, and with dr20:1. Furthermore, research shows that a weak coordination between the chiral rhodium catalyst and β,γ-unsaturated ketoesters was responsible for the high diastereoselectivity and enantioselectivity of the corresponding products.

Background Tea plants originated in southwestern China. Guizhou Plateau is an original center of tea plants, and is rich in germplasm resources. However, the genetic diversity, population structure and distribution characteristics of cultivated-type tea plants in the region are unknown. In this study, we explored the genetic diversity and geographical distribution of cultivated-type tea accessions in Guizhou Plateau. Results We used 112,072 high-quality genotyping-by-sequencing to analyze the genetic diversity, principal components, phylogeny, population structure, and linkage disequilibrium, and develop a core collection of 253 cultivated-type tea plant accessions from Guizhou Plateau. The results showed Genetic diversity of the cultivated-type tea accessions of the Pearl River Basin was significantly higher than that of the cultivated-type tea accessions of the Yangtze River Basin. Three inferred pure groups (CG-1, CG-2 and CG-3) and one inferred admixture group (CG-4), were identified by a population structure analysis, and verified by principal component and phylogenetic analyses. The highest genetic distance and differentiation coefficients were determined for CG-2 vs CG-3. The lower genetic distance and differentiation coefficients were determined for CG-4 vs CG-2 and CG-4 vs CG-3, respectively. We developed a core set and a primary set. The primary and core sets contained 77.0 and 33.6% of all individuals in the initial set, respectively. The primary set may serve as the primary population in genome-wide association studies, while the core collection may serve as the core population in multiple treatment setting studies. Conclusions The present study demonstrated the genetic diversity and geographical distribution characteristics of cultivated-type tea plants in Guizhou Plateau. Significant differences in genetic diversity and evolutionary direction were detected between the ancient landraces of the Pearl River Basin and the those of the Yangtze River Basin. Major rivers and ancient hubs were largely responsible for the genetic exchange between the Pearl River Basin and the Yangtze River Basin ancient landraces as well as the formation of the ancient hubs evolutionary group. Genetic diversity, population structure and core collection elucidated by this study will facilitate further genetic studies, germplasm protection, and breeding of tea plants.

Background Tea plants originated from the southwest of China. Guizhou is one of the origin center of tea plants, which is rich in tea plant germplasm resources. However, the distribution characteristics and transmission model of tea plant were still unclear. Results We collected 253 cultivated-type tea plant accessions from Guizhou plateau and analyzed the genetic diversity, PCA, phylogenetic, population structure, LD, and development of core collection using the genotyping-by-sequencing (GBS) approach. A total of 112,072 high-quality SNPs were identified, which was further used to analyze the genetic diversity and population structure. In this study, we found that the genetic diversity in cultivated-type tea accessions of PR Basin were significantly higher than that in cultivated-type tea accessions of YR Basin. Moreover, four groups, including three pure groups (CG-1, CG-2 and CG-3) and one admixture group (CG-4), were identified based on population structure analysis, which was verified by PAC and phylogenetic analysis. Our results showed that the highest GD and Fst values were found in CG-2 vs CG-3, followed by CG-1 vs CG-2 and CG-1 vs CG-3. The lowest GD and Fst values were detected in CG-4 vs CG-1, CG-4 vs CG-2, and CG-4 vs CG-3. Conclusions This study provided the evidence to confirm the contribution of PR and YR Basins and ancient hub road section to the transmission of cultivated-type tea accessions in Guizhou plateau. The genetic diversity, population structure and core collection revealed by our study will benefit further genetic studies, germplasm protection, and breeding.

Background The aim of this study was to investigate the effects and underlying mechanism of long non-coding RNA-differentiation antagonizing non-protein coding RNA (lncRNA-DANCR) on colorectal cancer (CRC). Methods The expression of lncRNA-DANCR in CRC and pericarcinous tissues from 40 CRC patients, and the expression in HT-29 cells and FHC cells, were determined by qRT-PCR. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The migration and invasion of CRC cells were detected by wound healing assay and transwell assay, respectively. HT-29 cells were transfected and divided into three groups: BLANK group, si-NC group and si-DANCR group. After transfection, the expression of lncRNA-DANCR was detected by qRT-PCR. The expression of E-cadherin and vimentin was detected by western blot and immunofluorescence. The mice model of xenograft tumor was established and histological changes of lung lobes sections were measured by hematoxylin-eosin (HE) staining. Results The expression of lncRNA-DANCR in CRC tissues and HT-29 cells was significantly higher than that in non-CRC tissues and FHC cells. Silencing lncRNA-DANCR could significantly inhibit the proliferation, invasion and metastasis of HT-29 cells. Western blot showed that the expression of E-cadherin increased significantly and vimentin decreased significantly after silencing lncRNA-DANCR. The same results were observed in immunofluorescence experiment. Silence of lncRNA-DANCR markedly suppressed the growth and metastasis of CRC. Conclusions LncRNA-DANCR may facilitate the growth and metastasis of CRC by regulating the epithelial-mesenchymal transition (EMT) process.

Correlation between morphological defects and device yield in the 4H-SiC epitaxial layers were investigated with overlapped morphological defect mapping and device yield mapping figures. The results show the harmful level of various morphological defects for device yield should be triangular > downfall > carrot > particle. Origins of the triangular defects were traced by a multiple cycle of polishing and molten KOH etching process, revealing that the triangular defects are mainly formed at initially epitaxial stage and caused by threading screw dislocations (TSDs) in substrates or spontaneous nucleation. Etching temperature and time of the hydrogen surface etching process and C/Si ratio in buffer layer growth process were also systematically optimized. The density of triangular defects can be reduced to 0.1 cm−2. Meanwhile, an additional buffer layer with a step-bunching surface was applied and can effectively restrain the extending of triangular defect along 〈1 −1 0 0〉 direction.

Bicyclo[3.2.1]octanes and related structures are unique units that widely exist in natural products, but the rapid and stereoselective construction of this skeleton is a challenging issue. We report the stereodivergent synthesis of bicyclo[3.2.1]octenes using Nazarov reagents and alkenyl 1,2-diketones with Bronsted base catalysis under mild conditions. Both stereoisomers of the bridged products can be obtained by tuning the reaction conditions, and cyclohexene product can also be selectively formed.

Previous studies demonstrated that prophylactic cranial irradiation (PCI) significantly reduced the incidence of brain metastases in patients with extensive disease small cell lung cancer (ED-SCLC). However, the appropriate timing for PCI in treating ED-SCLC is still unclear. This study aimed to compare the effect and safety of early versus late PCI. Between November 2011 and July 2016, 103 patients with ED-SCLC were reviewed, receiving appropriate imaging tests to exclude brain metastases prior to cranial irradiation. Of these 103 patients, early PCI was performed in 47 patients and the other 56 patients received late PCI. The primary endpoint was the incidence of brain metastases. The progression-free survival (PFS), overall survival (OS), and adverse events (AEs) were also assessed. Early PCI significantly lowered the risk of brain metastases, as compared to late PCI (p = 0.024). Additionally, multivariate analyses demonstrated that early PCI was a favorable independent predictor of the incidence of brain metastases. The PFS and OS of patients in the early and late PCI groups were comparable (PFS: 8.4 months vs. 7.5 months, p = 0.234; OS: 16.1 months vs. 15.2 months, p = 0.753). The AEs were generally acceptable in both groups. To reduce the incidence of brain metastases, early PCI is more effective than late PCI for ED-SCLC patients.

Gastric cancer has higher morbidity and mortality than other cancers for the low diagnosis rate and few therapies. MiR-195 has been reported to be involved in the occurrence, development and prognosis of various cancers. However, the function of miR-195 in gastric cancer remains largely unknown. Herein, the aims of this study were to probe the functional mechanism of miR-195 and its chemotherapy sensitivity as well as clinical prognosis in gastric cancer. We screened out low-expressed miR-195 through microarray analysis and further confirmed miR-195 was widely down-regulated in gastric cancer cells. Subsequently, AKT3 was identified as the direct target gene of miR-195 by target gene prediction software, dual luciferase reporter assay and western blot. Functional assays indicated that miR-195 acted as a tumor suppressor through regulating the proliferative, migrated and invasive properties of gastric cancer cells in vitro, and intratumoral delivery of miR-195 significantly suppressed tumor growth in vivo. Additionally, we also found miR-195 overexpression could enhance the chemotherapy sensitivity of cisplatin in gastric cancer cells and prolong the overall survival and progression free survival of gastric cancer patients. Collectively, our findings demonstrate miR-195 may be of great significance on early diagnosis of gastric cancer, providing the theoretical basis for prognosis and recurrence risk.

The resolution technique of stereodivergent reaction on racemic mixtures (stereodivergent RRM) was employed for the first time in ruthenium complex catalyzed transfer hydrogenation of racemic epoxy ketones, providing a new and very simple method that allows access to enantioenriched epoxy alcohols with three stereogenic centers in a one-step fashion. The protocol features simple reaction conditions, practical operation, ability to scale up, and broad group tolerance.

Table S1. Methodological quality of randomized controlled trials assessed using the Cochrane risk-of-bias tool. (DOC 30 kb)

Table S2. Methodological quality of cohorts assessed using the Newcastleâ Ottawa scale. (DOCX 18 kb)

Data S1. Search strategy in PubMed. (DOCX 17 kb)

The growth of 3C-SiC films on Si(100) substrates by low pressure hot-wall chemical vapor deposition is described. The investigation reveals that the C/Si ratio plays an important role in crystalline quality and surface morphology of 3C-SiC films. Comparisons of crystalline quality of 3C-SiC films with different C/Si ratio, indicate that the optimum C/Si ratio for high crystalline quality is 4.5. Noticeably, the polycrystalline grains of 3C-SiC films exhibit epitaxial nature with irregular shape and randomly distribution or pyramid-like shape and regular distribution along the 〈110〉 directions, which are dependent on the C/Si ratio. The changes in crystalline quality with increasing C/Si ratio are attributed to the competition of the formation of defects by excess carbon species and the etching of the atomic hydrogen. Meanwhile, the changes of surface morphology are due to the changes of secondary nucleation rate.

BACKGROUND There is increasing evidence that adenosine triphosphate (ATP), a well-known neurotransmitter and neuromodulator in the central nervous system, plays an important role as an extracellular chemical messenger in the cochlea. MATERIAL AND METHODS Using a whole-cell recording technique, we studied the effects of ATP on isolated Hensen's cells, which are supporting cells in the cochlea, to determine if they are involved in the transduction of ions with hair cells. RESULTS ATP (0.1-10 µM) reduced the potassium current (IK+) in the majority of the recorded Hensen's cells (21 out of 25 cells). An inward current was also induced by high concentrations of ATP (100 µM to 10 mM), which was reversibly blocked by 100 µM suramin (a purinergic antagonist) and blocked by nifedipine (an L-type calcium channel blocker). After the cochleas were perfused with artificial perilymph solutions containing nifedipine and exposed to noise, the amplitude increase in the compound action potential (CAP) threshold and the reduction in cochlear microphonics was lower than when they were exposed to noise alone. CONCLUSIONS Our results suggest that ATP can block IK+ channels at a low concentration and induce an inward Ca2+ current at high concentrations, which is reversed by purinergic receptors. Nifedipine may have a partially protective effect on noise-induced hearing loss (NIHL).

A modified method is applied to grow a void-free 3C-SiC thin film of better crystal quality on the Si(100) substrate in a mixed gas of C3H8, SiH4 and H2 using low pressure chemical vapor deposition. The modified method adds a low temperature and low pressure heat treatment step after the clean step and subsequent a high flow carbon-based precursor gas-on step. The X-ray intensity of the 3C-SiC(200) peak is enhanced intensively using this modified method. The better crystal quality of 3C-SiC is confirmed by both X-ray diffraction and Raman spectra data. The modified method leads to a better crystal quality and surface morphology of the 3C-SiC film grown on Si(100) due to the better carbonized surface morphology. Moreover, the modified method can completely remove the void formation during the whole process. Morphological and structure analysis using scanning electron microscopy and transmission electron microscopy reveal no void defects at the 3C-SiC/Si(100) interface.

In this work a porous material, an MCM-49/MCM-41 composite molecular sieve, was synthesized via a microwave assisted hydrothermal process and characterized to observe its optimal properties for heavy metal chromate removal. The adsorption properties of chromate onto MCM-49/MCM-41 and the factors that influence its adsorption, such as chromate concentration and contact time, were investigated. It was found that MCM-49/MCM-41 is micro/mesoporous with a surface area of 372 m2 g−1 and average pore size of 2.9 nm. The adsorption capacity of MCM-49/MCM-41 was as high as 4.10 mg g−1 for chromate at a temperature of 298 K, when the initial concentration of chromate was 50 mg L−1. The adsorption isotherm data of chromate fit well with both Freundlich and Langmuir adsorption isotherm models and the adsorption kinetics was well fitted using a pseudo-second order kinetic model. Thermodynamic parameters such as the standard Gibbs free energy (ΔG), enthalpy change (ΔH) and standard entropy change (ΔS) were also evaluated. Thermodynamic analysis indicates that the adsorption of chromate onto MCM-49/MCM-41 is a spontaneous and exothermic process. These results suggest that MCM-49/MCM-41 could serve as a promising adsorbent for potential applications in the removal of chromate from wastewater.

Carbon film is widely used in many fields due to its excellent electronic, mechanical, and chemical properties. In this work, a free-standing graphene-like carbon film was synthesized on SiC substrate by a CVD process with ethylene as the major carbon source. The carbon film can be easily exfoliated from the substrate completely without any residuum. Intensity of the 2D peak of graphene is strong, while the feature peaks of SiC is not observed in the Raman spectra. Meanwhile, no shift of the feature peaks was found in the Raman spectra for the samples with different growth time. Results show that the carbon film is formed by the carbon atoms which come from the decomposition of ethylene rather than the thermal sublimation of SiC substrate. Intensity ratio of 2D to G peak increases with carbon film thickness reduces, which means that few layers of graphene can be synthesized by reducing the thickness of the carbon film. Besides, the sheet resistivity of the sample is as low as 40 Ω/sq. The excellent electrical conductivity of such carbon film can be useful in some special field in the future, such as electricity and energy.

4H-Silicon carbide (SiC) epitaxial layers on the C-face SiC substrates are potentially useful for fabricating high-performance power SiC MOSFET device applications. In this research, 4H-SiC epilayers are prepared on 4° off-angle C-face 4H-SiC substrates through a low pressure chemical vapor deposition (CVD). Surface morphologies of the epilayers show a strong dependence on C/Si ratio, growth temperature and etching time. A specular surface morphology was obtained at the temperature of about 1550 °C, with the etching time of 15 min and C/Si ratio of 1.2.

A 4H-SiC MOSFET with breakdown voltage higher than 1200V has been successfully designed and fabricated. Numerical simulations have been performed to optimize the parameters of DMOSFET. The n-type epilayer is $10 \mu \mathrm{m}$ thick with a doping of $1\times 10^{16}\text{cm}^{-3}$ . The devices were fabricated with a floating guard ring edge termination. The drain current I d = 20 A at Vg = 20 V, corresponding to $\mathrm{V}_{\mathrm{d}}\leqslant 1.6\mathrm{V}$

The systematic study of p-doping SiC epitaxy layer was performed on 4H-SiC (0001) 4° off-axis substrates using a high growth rate planetary hot-wall chloride-based CVD system. The influence of C/Si ratio, main hydrogen flow rate and Cl/Si ratio on aluminum (Al)-doping concentration and intra wafer uniformity has been investigated. The concentration increases with the C/Si ratio and main hydrogen flow rate while decreases with the Cl/Si ratio. The doping uniformity as the embodiment of the shape of aluminum depletion profile with substrate rotation averaging is mainly affected by main hydrogen flow, and more or less unaffected by C/Si ratio and Cl/Si ratio. The main hydrogen flow rate optimizes the Al- depletion curve within reactor, resulting in an improvement of intra wafer incorporation uniformity.

1,2-Dihydronaphthalenes are important molecules in both medicinal and synthetic chemistry, but methods for the catalytic asymmetric construction of this class of molecules are limited. The diastereo- and enantioselective N-heterocyclic carbene-catalyzed cascade annulation reactions using benzodiketones and enals under oxidative conditions, which afford a variety of 1,2-dihydronaphthalenes with two adjacent stereocenters in up to 99% yield, with >20:1 dr, and up to 99% ee, are reported. Furthermore, the product can be easily transformed to a series of useful compounds such as alcohol, amide, and epoxide.

Blue rubber bleb nevus syndrome (BRBNS) is a rare disorder characterized by multiple recurrent vascular malformations, including hemangioma, which primarily locate on the skin and gastrointestinal (GI) tract. The present study reports a 22-year-old female with iron-deficiency anemia and recurrent episodes of melena. The patient also exhibited characteristic venous malformations of the skin. Endoscopy revealed several hemangiomas in the GI tract. The hemangiomas were treated by ligation using a nylon cord, while small blue mucosal polypoid lesions were treated using a sclerosing agent during colonoscopy and double-balloon enteroscopy. The patient was reviewed regularly for three years following surgery and no further bleeding episodes were noted.

A 4H-SiC MOSFET with breakdown voltage higher than 1200V has been successfully designed and fabricated. Numerical simulations have been performed to optimize the parameters of DMOSFET. The n-type epilayer is 10 μm thick with a doping of 6×1015 cm−3. The devices were fabricated with a floating guard ring edge termination. The drain current Id = 10 A at Vg = 20 V, corresponding to Vd = 2.0 V.

The asymmetric desymmetrization of 1,4-dienes via chiral N-heterocyclic carbene catalyzed Stetter-type umpolung reaction was demonstrated. A variety of differently substituted dienes were tolerated very well, affording cyclic ketones with two consecutive stereogenic centers (including one quaternary carbon) in moderate to high yields and with high to excellent enantioselectivities. This work expanded both reaction types of catalytic diene desymmetrizations and substrate diversity in NHC catalyzed desymmetric transformations.

The asymmetric desymmetrization of 1,4-dienes via chiral N-heterocyclic carbene catalyzed Stetter-type umpolung reaction was demonstrated. A variety of differently substituted dienes were tolerated very well, affording cyclic ketones with two consecutive stereogenic centers (including one quaternary carbon) in moderate to high yields and with high to excellent enantioselectivities. This work expanded both reaction types of catalytic diene desymmetrizations and substrate diversity in NHC catalyzed desymmetric transformations.

To evaluate the effect of prophylactic cranial irradiation (PCI) on overall survival (OS) in patients with extensive small cell lung cancer (ESCLC). Between April 2005 and May 2014, 204 patients with ESCLC who had any response (according to RECIST 1.1) to initial chemotherapy were reviewed. All patients had undergone appropriate imaging tests to exclude brain metastases before initial chemotherapy. PCI was performed on 45 patients (22.1 %) and the remaining patients (77.9 %) received no such treatment (control group). Primary endpoint was OS. The incidence of brain metastases, brain metastases-free survival (BMFS), and adverse effects were also evaluated. Survival data of the 204 patients were analyzed statistically. PCI significantly prolonged median OS from 12.6 to 16.5 months as compared to the control group (hazard ratio, HR, 0.63; 95 % confidence interval, CI, 0.41 to 0.96; p = 0.033). PCI significantly lowered the risk of brain metastases (HR 0.48; 95 % CI 0.30 to 0.76; p = 0.001). The 1‑year incidence of brain metastases was 17.1 and 55.9 % in the PCI and control group, respectively. PCI significantly correlated with the increased median BMFS (p = 0.002). Additionally, multivariate analyses demonstrated that PCI was a favorable independent predictor of OS, BMFS, and the incidence of brain metastases. Acute and chronic adverse effects were generally low grade and well tolerated in patients receiving PCI. PCI after any response to initial chemotherapy significantly improved OS of ESCLC patients analyzed in this study.

A rapid and inexpensive method was developed for the determination of trace silver in geological samples by using sulfhydryl cotton coupled with ICP-MS. The interferences such as , and on silver were investigated in detail. Sulfhydryl cotton was found to be an effective adsorbent for separation of interferences for Ag in the solutions. Excellent agreements with the certified values were obtained for all the certified reference materials. The memory effects of Ag by ICP-MS were examined by using different agents, including water, nitric acid, and HCl-thiourea to all standards/samples. The agents also acted as cleansing solutions. A combination of HCl with thiourea gave the minimum memory effect. For comparison of results, a proposed Chinese Geology Survey procedure DC-ARC-AES and a direct determination pretreatment method of ICP-MS (water bath- auqa regia digestion) were studied. Under optimal conditions, the detection limits of our method for and were 1.2 ng/g and 1.3 ng/g, which offered much better accuracy for some difficult analysis geological samples such as GBW07604, GBW07605.

Results are presented for the silicon carbide (SiC) vertical channel junction field effect transistor (VJFET) fabricated based on in-house SiC epitaxial wafer suitable for power devices. The Normally-off 1300V SiC VJFET device's current density is 260 A/cm 2 and current is 8 A at VG= 7 V and VD = 2 V, with related specific on-resistance 7.56 mΩ·cm 2 . The device exceeds 1300 V at gate bias VG = 0 V.

We conducted an open-label single-arm phase II study by combining irinotecan (FOLFIRI) and bevacizumab (BV) plus erlotinib (ER) in 2nd-line chemotherapy for patients with metastatic colorectal cancer (mCRC). Eligible mCRC patients received 1st-line standard chemotherapy but still had progressive disease. They were given FOLFIRI plus BV at 2.5 mg/kg on day 1 per 2-week cycle, and daily 150 mg ER. The primary endpoint is progression-free survival (PFS). A total of 122 patients enrolled in the study. Among them, 55.7% were male patients and median age was 58.4 years (29–72 years). Median PFS was 7.1 months (95% CI 4.3–10.2). Median overall survival (OS) was 13.5 months (95% CI 9.7–16.4). No patients had complete responses, 24 patients had partial response (19.6%) and 59 had stable disease (48.4%). The most frequent adverse event (AE) was rash, with 66 patients (54.1%) had grade 3/4 rash. Other frequent grade 3/4 AEs were fatigue (n = 36, 29.5%), bleeding (n = 31, 25.4%), neutropenia (n = 23, 18.9%), and platelets (n = 14, 11.5%). Combining FOLFIRI and BV plus ER in 2nd-line chemotherapy is efficient to treat mCRC patients with acceptable safety.

In this paper, we report theoretical consideration and simulation of a proposed III–V nanowire (NW)/Si triple-junction solar cell. The cell consists of two axially connected III–V NW subcells that are grown and electrically integrated on an active Si substrate. The optical properties of the cell are thoroughly analyzed by using the finite-difference time-domain method. It is found that NW subcells with optimized geometry have high absorption throughout their absorption region. Meanwhile, beyond the absorption edge of the top and middle NW subcells, the NWs act as an efficient antireflection coating for the bottom Si subcell due to the formation of an optical cavity within the NW layer. The physics responsible for the enhanced light harvesting process is qualitatively explained through modal analysis. In addition, we have shown that the condition of current matching in a III–V NW/Si multi-junction can be fulfilled by adjusting the diameter of the NWs. In order to study the current–voltage characteristics of the proposed cell, the optical generation profiles under AM1.5G illumination are incorporated into an electrical modeling. Our optoelectrical simulations indicate that, with an excellent current matching between subcells, the performance of the proposed structure is comparable with state-of-the-art multi-junction cells. The results presented here indicate that semiconductor NWs may provide a promising route toward high efficiency multi-junction solar cells.

We use moire fringes to experimentally characterize the transmission and filtering effect of surface plasmons (SPs) in the alternatively stacked metal-dielectric layers (ASMDLs). Two gratings with unequal periods are introduced at the two sides of films structure to excite SPs and generate moire fringes observable in the far-field. The observed moire fringes with specific period agree well with simulations and clearly demonstrate SP with corresponding wave vector transmission and filtering in ASMDLs. By applying variant incidence angle, the fringes contrast fluctuation further illustrate the transmission of SP in a specific wide wave vector band and with an uneven amplitude transmission profile.

GaAs nanowires (NWs) are grown on GaAs (311)B substrates by gold assisted molecular beam epitaxy technology. Combined scanning and transmission electron microscopy analyses, the crystallographic orientations of NWs are studied. It is found that crystallographic orientations of NWs are closely related to their crystal structures: NWs of zinc blende structure grow along 〈001〉 directions and NWs of wurtzite structure grow along 〈0001〉 directions. The influence of impinging Ga flux on morphology and crystal structure of the NWs is also discussed. It is observed that NWs prefer to grow along zinc blende 〈001〉 directions at lower Ga flux, while NWs tend to grow along the wurtzite 〈0001〉 directions with only a small portion along the zinc blende 〈001〉 direction at a higher Ga flux. The control of crystal structure and orientation of NWs can be achieved effectively by changing the Ga flux.

We investigated the quantum dots-templated growth of a (0001) GaN film on a c-plane sapphire substrate. The growth was carried out in a radio-frequency molecular beam epitaxy system. The enlargement and coalescence of grains on the GaN quantum dots template was observed in the atom force microscopy images, as well as the more ideal surface morphology of the GaN epitaxial film on the quantum dots template compared with the one on the AlN buffer. The Ga polarity was confirmed by the reflected high energy electron diffraction patterns and the Raman spectra. The significant strain relaxation in the quantum dots-templated GaN film was calculated based on the Raman spectra and the X-ray rocking curves. Meanwhile, the threading dislocation density in the quantum dots-templated film was estimated to be 7:1 10 7 cm −2 , which was significantly suppressed compared with that of the AlN-buffered GaN film. The roomtemperature Hall measurement showed an electron mobility of up to 1860 cm 2 /V s in the two-dimensional electron gas at the interface of the Al0:25Ga0:75N/GaN heterojunction.

A rigorous analysis and design of efficient light trapping for Gallium arsenide nanowire array (NWA) solar cells is presented. The influence of the geometric parameters on the optical absorption of NWA has been thoroughly analyzed by using finite-difference time-domain simulations. It is found that the NWA have superior absorption characteristic over thin-film due to the combined effects of intrinsic anti-reflection and efficient excitation of resonant modes. Optimized optical designs are obtained by maximizing the ultimate photocurrent under AM1.5G illumination. The photogeneration profiles under optimized conditions are incorporated into electrical modeling, in which the core-shell NWA solar cells exhibit 22.3% efficiency.