Reconstruction of Bandlimited Functions from?Unsigned Samples

We consider the recovery of real-valued bandlimited functions from the absolute values of their samples, possibly spaced nonuniformly. We show that such a reconstruction is always possible if the function is sampled at more than twice its Nyquist rate, and may not necessarily be possible if the samples are taken at less than twice the Nyquist rate. In the case of uniform samples, we also describe an FFT-based algorithm to perform the reconstruction. We prove that it converges exponentially rapidly in the number of samples used and examine its numerical behavior on some test cases.     

Single-shot multiple-delay crossed-beam spectral interferometry for measuring extremely complex pulses

We demonstrate a single-shot measurement technique based on spectral interferometry (SI) for measuring the complete intensity and phase vs. time of extremely complex ultrashort laser pulses. Ordinarily, such a method would require an extremely-high-resolution spectrometer, but, by temporally interleaving many SI measurements, each using a different reference-pulse delay, our method overcomes this need. It involves introducing a transverse time delay into the reference pulse by tilting its pulse front transversely to the spectrometer dispersion plane. The tilted reference pulse then gates the unknown pulse by interfering with it at the image plane of a low-resolution imaging spectrometer, yielding an effective increase in the delay range and spectral resolution—by a factor of 30 in our proof-of-principle implementation. Our device achieved a temporal resolution of ~ 130 fs and a temporal range of 120 ps. This simple device has the potential to measure even longer and more complex pulses.     

Probing the Reactivity and Radical Nature of Oxidized Transition Metal-Thiolate Complexes by Mass Spectrometry

Transition metal thiolate complexes such as [PPN]⁺[RuL₃]^- (PPN?=?bis(triphenylphosphoranylidene) ammonium and L?=?diphenylphosphinobenzenethiolate) are known to undergo addition reactions with unsaturated hydrocarbons via the formation of new C-S bonds in solution upon oxidation. The reaction mechanism is proposed to involve metal-stabilized thiyl radical intermediates, a new type of distonic ions such as [RuL₃]⁺ ion in the case of [PPN]⁺[RuL₃]^-. This study presents the reactivity and structure investigation of [RuL₃]⁺ by mass spectrometry (MS) in conjunction with ion/molecule reactions. The addition reactions of [RuL₃]⁺ with alkenes or methyl ketones in the gas phase are indeed observed, in agreement with the proposed mechanism. Such reactivity is also maintained by several fragment ions of [RuL₃]⁺, indicating the preserved thiyl diradical core structure is responsible for the addition reaction. The thiyl radical nature of [RuL₃]⁺ was further verified by the ion/molecule reaction of [RuL₃]⁺ with dimethyl disulfide, in which the characteristic CH₃S? transfer occurs, both at atmospheric pressure and also at low pressure (~mTorr). These results provide, for the first time, clear mass spectrometric evidence of the radical nature of [RuL₃]⁺ (i.e., the distonic ion structure of [RuL₃]⁺), arising from the oxidation of non-innocent thiolate ligands of the complex [PPN]⁺[RuL₃]^-. Similar thiolate complexes, including ReL₃ and NiL₂, were also examined. Although reactions of oxidized ReL₃ or NiL₂ with CH₃SSCH₃ take place at atmospheric pressure, the corresponding reaction did not occur in vacuum. Consistent with these data, the addition of ethylene was not observed either, indicating lower reactivities of [ReL₃]⁺ and [NiL₂]⁺ in comparison to [RuL₃]⁺.      

Effect of plasma on modal dispersion characteristics of elliptical Bragg waveguide

In this paper, the dispersion characteristics of a plasma filled elliptical Bragg waveguide is investigated. The modal characteristic equations of the proposed Bragg waveguide for both ω > ω_p and ω < ω_p are derived. The effects of plasma frequency, numbers of cladding layers and the eccentricity of elliptical Bragg waveguide on the dispersion characteristics are studied. The analysis shows that the introduction of plasma in the proposed waveguide allows to control the propagation of modes.     

Synthesis of Pyrazole Derivatives Possessing Anticancer Activity: Current Status

Pyrazole is a versatile lead compound to design potent bioactive molecules for drug discovery and development, particularly in cancer therapy. The aim of this review is to present the most recent deeds in the field of synthetic route made for functionalized pyrazole derivatives active against cell proliferation disease. The review article covers the synthesis of 1H-pyrazole, synthesis of N-substituted pyrazoles, synthesis of pyrazolopyrazoles, and synthesis of pyrazoles fused with a naturally occurring moiety. Some of these reported compounds have passed the preclinical or initial-phase clinical trials for their anticancer activity.     

In(OTf)3-mediated dehydrative annulation of β-ketothioamides with phenylglyoxal: one-pot access to diversely functionalized pyrrol-2-thiones

Indium triflate mediated first synthesis of diversely functionalized pyrrol-2-thiones has been developed by dehydrative annulation of β-ketothioamides with phenylglyoxal through the domino Knoevenagel condensation/cyclization cascade in one-pot. This new simple strategy not only utilizes readily accessible starting material, but also allows the construction of 5-membered azaheterocycle with one quaternary carbon center as a result of the formation of two new (C–C and C–N) bonds in a single operation.     

Rhodium‐Catalyzed Intramolecular [3+2+2] Cycloadditions between Alkylidenecyclopropanes,Alkynes, and Alkenes

A Rh‐catalyzed intramolecular [3+2+2] cycloaddition is reported. The cycloaddition affords synthetically relevant 5,7,5‐fused tricyclic systems of type 2 from readily available dienyne precursors. The transformation takes place with moderate or good yields, high diastereoselectivity, and total chemoselectivity.     

Use of radiofrequency power to enable glow discharge optical emission spectroscopy ultrafast elemental mapping of combinatorial libraries with nonconductive components: nitrogen-based materials

Combinatorial chemistry and high-throughput techniques are an efficient way of exploring optimal values of elemental composition. Optimal composition can result in high performance in a sequence of material synthesis and characterization. Materials combinatorial libraries are typically encountered in the form of a thin film composition gradient which is produced by simultaneous material deposition on a substrate from two or more sources that are spatially separated and chemically different. Fast spatially resolved techniques are needed to characterize structure, composition, and relevant properties of these combinatorial screening samples. In this work, the capability of a glow discharge optical emission spectroscopy (GD-OES) elemental mapping system is extended to nitrogen-based combinatorial libraries with nonconductive components through the use of pulsed radiofrequency power. The effects of operating parameters of the glow discharge and detection system on the achievable spatial resolution were investigated as it is the first time that an rf source is coupled to a setup featuring a push-broom hyperspectral imaging system and a restrictive anode tube GD source. Spatial-resolution optimized conditions were then used to characterize an aluminum nitride/chromium nitride thin-film composition spread. Qualitative elemental maps could be obtained within 16.8 s, orders of magnitude faster than typical techniques. The use of certified reference materials allowed quantitative elemental analysis maps to be extracted from the emission intensity images. Moreover, the quantitative procedure allowed correcting for the inherent emission intensity inhomogeneity in GD-OES. The results are compared to quantitative depth profiles obtained with a commercial GD-OES instrument.     

14.31 % Power Conversion Efficiency of Sn-Based Perovskite Solar Cells via Efficient Reduction of Sn4+

The photoelectric properties of nontoxic Sn-based perovskite make it a promising alternative to toxic Pb-based perovskite. It has superior photovoltaic performance in comparison to other Pb-free counterparts. The facile oxidation of Sn²⁺ to Sn⁴⁺ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn⁴⁺ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi-interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn⁴⁺ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long-term stability.