Enhancement Of Peak Intensity Research Articles

A Millimetre-Wave Cuboid Solid Immersion Lens with Intensity-Enhanced Amplitude Mask Apodization

Photonic jet is a narrow, highly intensive, weak-diverging beam propagating into a background medium and can be produced by a cuboid solid immersion lens (SIL) in both transmission and reflection modes. Amplitude mask apodization is an optical method to further improve the spatial resolution of a SIL imaging system via reduction of waist size of photonic jet, but always leading to intensity loss due to central masking of the incoming plane wave. In this letter, we report a particularly sized millimetre-wave cuboid SIL with the intensity-enhanced amplitude mask apodization for the first time. It is able to simultaneously deliver extra intensity enhancement and waist narrowing to the produced photonic jet. Both numerical simulation and experimental verification of the intensity-enhanced apodization effect are demonstrated using a copper-masked Teflon cuboid SIL with 22-mm side length under radiation of a plane wave with 8-mm wavelength. Peak intensity enhancement and the lateral resolution of the optical system increase by about 36.0% and 36.4% in this approach, respectively.

Enhanced second harmonic generation from a plasmonic Fano structure subjected to an azimuthally polarized light beam

We show that an azimuthally polarized beam (APB) excitation of a plasmonic Fano structure made by coupling a split-ring resonator (SRR) to a nanoarc can enhance second harmonic generation (SHG). Strikingly, an almost 30 times enhancement in SHG peak intensity can be achieved when the excitation is switched from a linearly polarized beam (LPB) to an APB. We attribute this significant enhancement of SHG to the corresponding increase in the local field intensity at the fundamental frequency of SHG, resulting from the improved conversion efficiency between the APB excitation and the plasmonic modes of the Fano structure. We also show that unlike LPB, APB excitation creates a symmetric SHG radiation pattern. This effect can be understood by considering an interference model in which the APB can change the total SHG far-field radiation by modifying the amplitudes and phases of two waves originating from the individual SRR and nanoarc of the Fano structure.

Study on the diagnosis of metastatic hepatic neuroendocrine neoplasms by contrast-enhanced ultrasound

Objective To retrospectively analyze the contrast-enhanced ultrasound (CEUS) features of metastatic hepatic neuroendocrine neoplasm (MHNEN) and their diagnostic value. Methods Twenty-eight patients with 35 MHNEN lesions were enrolled in this retrospectively study and underwent CEUS examination. The dynamic enhancement features, including enhancement pattern, peak intensity, and washout pattern were analyzed. Results The arrival time of contrast agent, time to peak, time to iso-echogenity and time to hypo-echogenity was (15.96±4.14)s, (21.42±5.01)s, (29.41±4.83)s and (42.06±22.84)s, respectively. Compared with adjacent liver parenchyma, rapid enhancement, synchronous enhancement and slow enhancement were found in 42.9% (15/35), 48.6%(17/35), 8.5%(3/35) of MHNEN lesions, respectively. As for enhancement patterns, 82.9% (29/35) of MHNEN lesions showed global enhancement, while 17.1%(6/35) showed rim-like enhancement. In addition, 22.9%(8/35) of the selesions had a centripetal pattern during the arterial phase. Compared with liver parenchyma, all lesions demonstrated hyper-enhancement at peak enhancement. In portal venous phase, 68.6%(24/35) of MHNEN lesions presented marked hypo-enhancement and 31.4%(11/35) with slight hypo-enhancement. And in late phase, all the lesions showed marked hypo-enhancement.Moreover, the boundaries of the lesions became distinct after contrast injection and another 36 lesions were identified on CEUS compared with conventional ultrasound. Conclusions CEUS can afford more diagnostic information of MHNEN and may be a good technique for diagnosing MHNEN. Key words: Contrast enhanced ultrasound; Liver neoplasms; Neuroendocrine neoplasm; Neoplasms metastasis

Synthesis of CeOx/γ-Al2O3 catalyst for the NH3-SCR of NOx

Cerium oxide catalysts (CeOx) supported on γ-Al2O3 for high temperature (T >200°C) selective catalytic reduction (SCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O2 were prepared by a facile sol-gel method. Firstly, alumina was prepared by a precipitation technique. Field Emission Scanning Electron Microscope (FESEM) image of the support showed a spherical and uniform morphology with nano-metric particles. X-ray diffraction (XRD) pattern revealed that gamma alumina phase was formed. The effects of reaction temperature (T=200–400°C) and CeOx loading (4–19wt%) were investigated on NOx conversion and selectivity to N2 as a desired product. XRD and Brunauer, Emmett & Teller (BET) surface area analyzes showed that increasing the CeOx loading enhanced peak intensity and crystallite size of CeOx and declined the total surface area, respectively. H2-temperature programmed reduction (TPR) results showed the presence of cerium oxide in form of CeO2 with a maximum normalized H2 consumption of 4.18mmolg−1 catalyst for 14wt% CeOx. Under the reaction conditions of 300°C, 1bar, NONH3=900ppm, O2=5vol%, GHSV=30,000h−1 and 14wt% CeOx, NOx conversion and N2 selectivity were 97% and 99%, respectively. It can be concluded that proper crystallite size, surface area, number of active sites and good redox ability might be effective for the excellent performance of 14wt% CeOx.

Clinical value of combining transvaginal contrast-enhanced ultrasonography with serum human epididymisprotein-4 and the resistance index for early-stage epithelial ovarian cancer.

Objectives:To increase accuracy of the detection and differential diagnosis of the early epithelial ovarian cancer (EOC) with transvaginal contrast-enhanced ultrasonography (TVCEUS) combining serum human epididymisprotein 4 (HE4), and resistance index (RI).Methods:This retrospectively case-control study of 230 patients with ovarian tumors were reviewed at the Department of Gynecology and Obstetrics, Zhongnan Hospital, Wuhan University, Wuhan, China between June 2008 and September 2015. Before the operation of 110 cases with EOC (Group A) and 120 cases of patients with benign ovarian tumor (Group B), we observe and calculate both Groups’ tumor vascular contrast-enhanced ultrasonography morphology scores (U), time-intensity curve (TIC) of contrast-enhanced ultrasonography, HE4, and RI. Results were compared with the histopathological analysis results.Results:The ultrasonography morphology scores, peak intensity (PI) enhancement rate (ER) with the parameters of the TIC and HE4 are higher in Group A compared with patients in Group B and the RI was lower than Group B. The detection rates for all indexes in the benign and malignant groups and their comparisons to the histopathological results were determined. The detection rate differences for HE4 (p=0.001), RI (p=0.001), U (p=0.001), PI (p=0.001), and ER (p=0.001) were all statistically significant (p<0.05).Conclusion:The high clinical value through combined TVCEUS, HE4, and RI detection can increase the sensitivity of the diagnosis and differential diagnosis of the early EOC.

The correlation between HER-2 expression and the CEUS and ARFI characteristics of breast cancer.

ObjectiveThe purpose of the present study was to explore the correlation between the contrast-enhanced ultrasound (CEUS) and acoustic radiation force impulse (ARFI) characteristics of breast cancers and the expression of human epidermal growth factor receptor 2 (HER-2).MethodsHER-2 expression levels in the tumor masses of 167 clearly diagnosed cases of breast cancer were measured and analyzed. The enhancement features and time intensity curve (TIC) of CEUS and virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ) technology of ARFI were employed to analyze the relationship between HER-2 expression and the CEUS and ARFI characteristics of breast cancer.Results(1) Statistically significant differences in the distribution of the contrast agent, perforator blood flow, the overranging phenomenon and perfusion defects between the study groups with different HER-2 expression levels (P < 0.05) were observed on CEUS. In addition, statistically significant differences in the TIC peak time (PT), slope of the ascending branch (K) and area under the curve (AUC) were found in the groups expressing different levels of HER-2 (P < 0.05). In contrast, the degree of contrast agent enhancement and TIC peak intensity (PI) were found to be independent of the expression status of HER-2, as they were not statistically significant (P > 0.05). (2) Statistically significant differences in the VTQ results between the groups with different HER-2 expression levels were found (P < 0.05). However, no statistically significant differences in VTI image characteristics were detected between the groups expressing different levels of HER-2 (P > 0.05).ConclusionA correlation was found between the CEUS and ARFI characteristics of breast cancer and HER-2 expression levels. This correlation was principally reflected in perfusion defects, perforator blood flow, PI, PT, K and VTQ.

Capillary Ion Chromatography Using 18-Crown-6 Ether as Eluent Additive for the Separation of Anions

The retention behavior of inorganic anions was investigated on a hydrophobic stationary phase dynamically modified with 18-crown-6 ether (18C6) in capillary ion chromatography. Styrene–divinylbenzene copolymeric (polystyrene) packing material was used as the hydrophobic stationary phase to retain 18C6. The eluent contained 18C6, salt and acetonitrile; 18C6 was retained on the stationary phase and the analytes anions were separated by the cations, which were trapped on the 18C6 and worked as the anion-exchange sites. The effect of eluent conditions, such as eluent cation species, acetonitrile (ACN), 18C6, and salt concentrations (in this case, potassium chloride was used), was investigated. The retention times of inorganic anions decreased with increasing concentration of ACN. In case ACN concentration was less than 4%, the retention times decreased with the passage of time. The retention time of inorganic anions increased with increasing concentrations of 18C6 and potassium chloride concentrations. By contrast, high concentration of 18C6 and chloride in eluent promotes elution of inorganic anions, and the retention time decreased. Furthermore, a contactless conductivity detector was used to replace the conventional UV detector to obtain higher sensitivity detection. Separation of inorganic anions was achieved with the eluent containing potassium hydroxide and enhanced peak intensity was observed using a suppressed contactless conductivity detection.

Degree of functionalisation dependence of individual Raman intensities in covalent graphene derivatives

Covalent functionalisation of graphene is a continuously progressing field of research. The optical properties of such derivatives attract particular attention. In virtually all optical responses, however, an enhancement in peak intensity with increase of sp3 carbon content, and a vanishing of the peak position shift in monolayer compared to few-layer systems, is observed. The understanding of these seemingly connected phenomena is lacking. Here we demonstrate, using Raman spectroscopy and in situ electrostatic doping techniques, that the intensity is directly modulated by an additional contribution from photoluminescent π-conjugated domains surrounded by sp3 carbon regions in graphene monolayers. The findings are further underpinned by a model which correlates the individual Raman mode intensities to the degree of functionalisation. We also show that the position shift in the spectra of solvent-based and powdered functionalised graphene derivatives originates predominantly from the presence of edge-to-edge and edge-to-basal plane interactions and is by large functionalisation independent.

Cooperative enhancement of the nonlinear optical response in conjugated energetic materials: A TD-DFT study.

Conjugated energetic molecules (CEMs) are a class of explosives with high nitrogen content that posses both enhanced safety and energetic performance properties and are ideal for direct optical initiation. As isolated molecules, they absorb within the range of conventional lasers. Crystalline CEMs are used in practice, however, and their properties can differ due to intermolecular interaction. Herein, time-dependent density functional theory was used to investigate one-photon absorption (OPA) and two-photon absorption (TPA) of monomers and dimers obtained from experimentally determined crystal structures of CEMs. OPA scales linearly with the number of chromophore units, while TPA scales nonlinearly, where a more than 3-fold enhancement in peak intensity, per chromophore unit, is calculated. Cooperative enhancement depends on electronic delocalization spanning both chromophore units. An increase in sensitivity to nonlinear laser initiation makes these materials suitable for practical use. This is the first study predicting a cooperative enhancement of the nonlinear optical response in energetic materials composed of relatively small molecules. The proposed model quantum chemistry is validated by comparison to crystal structure geometries and the optical absorption of these materials dissolved in solution.

Au concentration‐dependent quenching of Raman 2D peak in graphene

We investigate the effect of sputtered gold nanoclusters (AuNCs) on the Raman spectra of graphene. The two prominent Raman peaks of graphene – 2D and G – show drastically different behaviour with AuNC introduction. The Raman 2D peak intensity decreases with gold coverage and finally is quenched for moderate gold nanoparticle coverage, while the G peak shows a AuNC size‐dependent enhancement in peak intensity. The quenching of the 2D peak is attributed to the hybridization of graphene's 2pz orbital with the 5d orbitals of Au. The G peak enhancement is due to the surface‐enhanced Raman scattering induced by the surface plasmons created in the AuNC by the incident laser beam (He–Ne laser, wavelength = 632.8 nm). The existence of surface plasmons is independently confirmed by UV‐visible spectrophotometry measurements. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Hybrid opto-chemical doping in Ag nanoparticle-decorated monolayer graphene grown by chemical vapor deposition probed by Raman spectroscopy

The novel opto-chemical doping effect in Ag nanoparticle-decorated monolayer graphene grown by chemical vapor deposition has been investigated using Raman spectroscopy for the first time. We used both noble metal nanoparticles and optical excitation, in a hybrid opto-chemical route, to tune the doping level in graphene. Metal nanoparticle-induced chemical effects and laser power-induced substrate effects alter the doping nature of graphene from p- to n-type. Compared with earlier studies, the proposed method significantly lowers the laser intensity required for optical power-dependent doping, resulting in prevention of damage to the sample due to local heating. Some other interesting observations are the enhanced peak intensity in the Raman spectrum of graphene, enhancement of the D-band intensity and the introduction of G-band splitting. This novel, cheap and easily implemented hybrid optical–chemical doping strategy could be very useful for tuning graphene plasmons on the widely used Si/SiO2 substrates for various photonic device applications.

Modifications of optical properties in doped germanene nanosheet

Optical properties, like complex dielectric constant, absorption coefficient, refractive index and reflectivity have been analysed via density functional theory (DFT) of As and Ga doped free standing (FS) germanium (Ge) nanosheet. Position dependent (same or different sub-lattice positions) doping mechanism of foreign elements along with concentration variation up to 6.25%, in pristine germanene layer has been adopted for the whole work. Interesting modifications in optical anisotropy than pristine layer have been observed as a consequence of doping. Such modifications, like enhancement or reduction of peak intensity or shifting of peak positions may be useful to design smart germanene based opto-electronics devices in upcoming future.

Modifications of optical properties in doped germanene nanosheet

Optical properties, like complex dielectric constant, absorption coefficient, refractive index and reflectivity have been analysed via density functional theory (DFT) of As and Ga doped free standing (FS) germanium (Ge) nanosheet. Position dependent (same or different sub-lattice positions) doping mechanism of foreign elements along with concentration variation up to 6.25%, in pristine germanene layer has been adopted for the whole work. Interesting modifications in optical anisotropy than pristine layer have been observed as a consequence of doping. Such modifications, like enhancement or reduction of peak intensity or shifting of peak positions may be useful to design smart germanene based opto-electronics devices in upcoming future.

Enhanced Performance of Electrochemical Sensors Based on Nanosized NiO Particles

A novel NiO nanoparticles modified screen printed electrode (SPE) was developed that couples the easy-to-use advantages of this technology to the pseudocapacitance properties of NiO. In order to find the conditions for achieving the best performing modified SPEs, NiO nanoparticles were purposely synthesized via a microwave assisted procedure followed by calcination at 400°C or 600°C. The two sets of NiO nanoparticles were dispersed in various solvents and at different loads. The structural and electrochemical characterization was carried on by X-ray Diffraction, Scanning Electron Microscopy and Cyclic Voltammetry using ferricyanide as electroactive probe. It was found that, in general, all modified electrodes show better performances compared to the bare electrodes. It must also be noted that the nanoparticles undergo a partial re-aggregation on the electrode surface. The best performing electrode is the one modified with NiO calcined at 400°C (the NiO400/H2O), which is also the one most homogenously dispersed on the electrode surface. Probed against several compounds, the NiO400/H2O modified electrode demonstrates superior electrochemical performances, with respect to literature data in terms of peak intensity enhancement relative to the bare electrodes and resolution of the reduction peaks.

Emission efficiency enhanced by reducing the concentration of residual carbon impurities in InGaN/GaN multiple quantum well light emitting diodes.

A series of samples with varying growth pressure are grown and their optical and structural properties are investigated. It is found that the residual carbon concentration decreases when the reactor pressure increases from 80 to 450 Torr during the InGaN/GaN multiple quantum well growth. It results in an enhanced peak intensity of electroluminescence because carbon impurities can induce deep energy levels and act as non-radiative recombination centers in InGaN layers.

ZnO thin films prepared by atomic layer deposition at various temperatures from 100 to 180 °C with three-pulsed precursors in every growth cycle

Zinc oxide (ZnO) thin films are grown at various temperatures from 100 to 180 °C by atomic layer deposition (ALD) with three-pulsed precursors per ALD cycle on sapphire (0001) substrates. In the texture analyses of x-ray diffraction (XRD), hexagonal (002) and (101) crystalline orientations are shown. The dominant diffraction is (002) above 140 °C and (101) at and below 140 °C. Hall effect measurements demonstrate remarkable decrease of free electron concentration below 140 °C and the lowest value is 2.4 × 1016 cm−3 at 100 °C. Photoluminescence (PL) spectra of samples display no defect-related luminescence band. The emission peak energy of PL spectra show blueshift with the increase of temperature from 100 to 140 °C, which is originated from band-filling (Burstein–Moss) effect. However, redshift occurred at temperature above 140 °C owing to bandgap renormalization (shrinkage) with the increase of free electron concentration. Enhancement of PL peak intensity and reduction of free electron concentration below 140 °C result from the large decline of intrinsic donor-like defects. 140 °C is a critical temperature for thermal activation of donors-like defects and alteration of dominant crystalline orientation as well as the electrical and optical behaviors in ZnO. The growth method also constitutes smooth surface of ZnO when it comes to the analysis of surface roughness of samples from topographic image forming by atomic force microscope (AFM).

Ellipsoidal plasma mirror focusing of high power laser pulses to ultra-high intensities

The design and development of an ellipsoidal F/1 focusing plasma mirror capable of increasing the peak intensity achievable on petawatt level laser systems to &amp;gt;1022 W cm−2 is presented. A factor of 2.5 reduction in the focal spot size is achieved when compared to F/3 focusing with a conventional (solid state) optic. We find a factor of 3.6 enhancement in peak intensity, taking into account changes in plasma mirror reflectivity and focal spot quality. The sensitivity of the focusing plasma optic to misalignment is also investigated. It is demonstrated that an increase in the peak laser intensity from 3×1020 W cm−2 to 1021 W cm−2 results in a factor of 2 increase in the maximum energy of sheath-accelerated protons from a thin foil positioned at the focus of the intense laser light.

Effects of ultraviolet-assisted electrochemical etching current densities on structural and optical characteristics of porous quaternary AlInGaN alloys

Effects of ultraviolet-assisted photo-electrochemical (PEC) etching current densities (J=20, 40, 80, and 160mA/cm2) towards structural, physical, and optical properties of aluminium indium gallium nitride (AlInGaN) semiconductors as well as corresponding schematized mechanism were studied and discussed. Formation of porous AlInGaN semiconductors at J lower than 80mA/cm2 has led to the acquisition of larger lattice parameters c and a, out-of-plane strain, in-plane strain, and hydrostatic strain as compared to the non-porous semiconductor, owing to the generation of more vacancy-type defects in the porous AlInGaN semiconductors. For the porous semiconductor formed at J greater than 80mA/cm2, the etching was affected by a limited mass transport of electrons and holes for anodic oxidation and cathodic reduction. According to the band gap (Eg) and Urbach energy (UE) determined from photoluminescence (PL) shift and UV–Vis absorption measurement, the vacancy-type defects were revealed as the radiative localized states that led to the enhancement in PL peak intensity. The acquisition of a lower density of dislocation-type defects in the porous semiconductors in contrast to the non-porous one on the other hand indicated that the dislocations were the non-radiative recombination centres, in which much of the density has been eliminated after PEC etching in the 1% potassium hydroxide electrolyte.

Electrically Driven Random Laser Memory

The first electrically driven random laser diode with nonvolatile resistive random access memory functionality is designed and demonstrated. To illustrate the working principle, a metal–insulator–semiconductor structure based on Pt/MgO/ZnO thin‐film layers is fabricated on indium tin oxide glass. The current–voltage curve of the dual‐function random laser memory (RLM) device exhibits an excellent electrical bistability with a high ON/OFF current ratio (≈107). The random lasing behavior is simultaneously demonstrated by using electrical pumping with the appearance of sharp‐peak emissions and a drastic enhancement of peak intensity. A wide angle‐dependent electroluminescence not only reveals its emitting advantage but also further supports the origin of random lasers. The first proof‐of‐concept presentation of RLM possesses several advantages of dual memory and lasing functions, which enables to open up new avenues to practical applications, such as light emitting memories for electrical and optical communication. This new horizon for the realization of all optical memories should therefore be able to attract academic as well as industrial interests. It is stressed here that the electrical reading of conventional memory array is usually in serial sequence, which limits the maximum data throughput. This hurdle can be overcome by optically readable memory devices.

Diagnostic value of contrast-enhanced ultrasound of thyroid nodules coexisting with Hashimoto's thyroiditis.

To evaluate the value of contrast-enhanced ultrasound (CEUS) in diagnosing thyroid nodules coexisting with Hashimoto's thyroiditis (HT). Totally 62 thyroid nodules in 48 HT patients were retrospectively analyzed. The CEUS characteristics were reviewed, and diagnostic value of enhancement pattern and peak intensity were calculated. Peak intensity (P=0.002) and enhancement pattern (P<0.001) differed significantly between malignant and benign thyroid nodules. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of heterogeneous enhancement were 97.6%, 85.7%, 93.0%, 94.7%, and 93.5%, respectively. Sensitivity, specificity, PPV, NPV and accuracy of low intensity at peak time were 85.4%, 52.4%, 77.8%, 64.7%, and 74.2%, respectively. Heterogeneous enhancement is effective in the diagnosis of malignant thyroid nodules coexisting with HT. CEUS can improve the diagnostic accuracy in distinguishing thyroid nodules with unknown malignancy under the conventional ultrasound.