Existence of Optimal Controls for Semilinear Parabolic Equations without Cesari-Type Conditions

Abstract. Optimal control problems governed by semilinear parabolic partial differential equations are considered. No Cesari-type conditions are assumed. By proving the existence theorem and the Pontryagin maximum principle of optimal ``state-control" pairs for the corresponding relaxed problems, an existence theorem of optimal pairs for the original problem is established.     

新型(4-HBA)SbX5·H2O类钙钛矿单晶及其卤素结构对发光特性的调控(英文)

发光材料因其在照明、显示、成像等方面的广泛应用而备受关注。作为新兴发光材料之一,钙钛矿类材料的研究及报道较多。其中,铅基钙钛矿的研究取得了巨大进展,光致发光量子产率(PLQY)几乎达到了100%。然而,基于铅基钙钛矿化学毒性和低稳定性,在实际应用过程中需要特殊的封装,因而提高了生产成本并限制了其实际应用领域。被广泛关注的锡基钙钛矿的荧光量子产率几乎能达到90%,但Sn²⁺易氧化成Sn⁴⁺,在空气中极不稳定。相较于铅基钙钛矿和锡基钙钛矿,锑基钙钛矿的低化学毒性、高热稳定性等优点突出。此外,锑基钙钛矿的光学性能在过去几年中也取得了很大的进展,有望突破传统钙钛矿应用的局限。在此,我们报道了一系列新型单晶(4-HBA)SbX₅·H₂O (4-HBA为4-羟基苄胺缩写,X为Cl或Br)。利用溶剂热法可制备高质量的(4-HBA)SbBr₅·H₂O、(4-HBA)SbBr₃Cl₂·H₂O和(4-HBA)S...     

RNA-templated single-base mutation detection based on T4 DNA ligase and reverse molecular beacon

A novel RNA-templated single-base mutation detection method based on T4 DNA ligase and reverse molecular beacon (rMB) has been developed and successfully applied to identification of single-base mutation in codon 273 of the p53 gene. The discrimination was carried out using allele-specific primers, which flanked the variable position in the target RNA and was ligated using T4 DNA ligase only when the primers perfectly matched the RNA template. The allele-specific primers also carried complementary stem structures with end-labels (fluorophore TAMRA, quencher DABCYL), which formed a molecular beacon after RNase H digestion. One-base mismatch can be discriminated by analyzing the change of fluorescence intensity before and after RNase H digestion. This method has several advantages for practical applications, such as direct discrimination of single-base mismatch of the RNA extracted from cell; no requirement of PCR amplification; performance of homogeneous detection; and easily design of detection probes.     

Characterization of constituents in Stellera chamaejasme L. by rapid-resolution liquid chromatography-diode array detection and electrospray ionization time-of-flight mass spectrometry

A reliable and rapid method based on rapid-resolution liquid chromatography-diode array detection (RRLC-DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF/MS) has been developed for the isolation and characterization of multiple constituents in the root of Stellera chamaejasme L., which was extracted by sonication with methanol in an optimized procedure. Separation of the multiple constituents was achieved on an Agilent Zorbax XDB-C18 (50x3.0 mm i.d.; 1.8 microm) column using a gradient elution at a flow rate of 0.4 mL/min. The detection wavelength was 210 nm. Mass spectra were acquired in both positive and negative modes. A formula database of the known chemical constituents in the root of Stellera chamaejasme L. was established by an Agilent software. Twenty-two obvious peaks appeared in the total ion chromatogram and nine of them were characterized by TOF/MS. The RRLC-DAD and ESI-TOF/MS method with ultrasonic extraction would be useful for rapid and effective characterization of chemical constituents in the root of Stellera chamaejasme L.     

Highly Efficient Regioselective Synthesis of 5′-<Emphasis Type="Italic">O</Emphasis>-lauroyl-5-azacytidine Catalyzed by <Emphasis Type="Italic">Candida antarctica</Emphasis> Lipase B

Enzymatic regioselective acylation of 5-azacytidine with vinyl laurate was successfully conducted with an immobilized lipase from Candida antarctica type B (i.e., Novozym 435) for the first time. The acylation of 5-azacytidine took place at its primary hydroxyl group and the desired product 5′-O -lauroyl-5-azacytidine could be prepared with high reaction rate, high conversion, and excellent regioselectivity. The influences of several key variables on the enzymatic acylation were also systematically examined. Pyridine was found to be the best reaction medium. The optimum initial water activity, the molar ratio of vinyl laurate to 5-azacytidine and reaction temperature were 0.07, 30:1, and 50 °C, respectively. Under the optimized conditions described above, the initial reaction rate, the substrate conversion, and the regioselectivity were as high as 0.58 mM/min, 95.5%, and >99%, respectively, after a reaction time of around 5 h.     

Synthesis and characterization of 5-fluorocytosine intercalated Zn-Al layered double hydroxide

In this paper, the intercalation of 5-fluorocytosine (5-FC) into a layered inorganic host, Zn-Al layered double hydroxide (LDH), has been carried out using coprecipitation method to obtain 5-FC/LDH nanohybrids. The intercalated amount (A_In) of 5-FC into the LDH is remarkably dependent on the molar ratio (R_F/M) of 5-FC to metal ions and the pH of coprecipitation system. The morphology of 5-FC molecules in 5-FC/LDH nanohybrids is dependent on the A_In. It is interestingly found that the morphology of the nanohybrid particles may be changed with the increase of R_F/M from hexagonal plate particles to threadlike particles. The in vitro drug release from the nanohybrids is remarkably lower than that from the corresponding physical mixture and pristine 5-FC at either pH 4.8 or pH 7.5. In addition, the release rate of 5-FC from the nanohybrid at pH 7.5 is remarkably lower than that at pH 4.8, this is due to a possible difference in the release mechanism. The obtained results show these drug-inorganic nanohybrids can be used as a potential drug delivery system.     

LC Determination and Bioequivalence Study of Pantoprazole in Human Plasma

A selective and sensitive liquid chromatography (LC) method with rapid sample processing was developed for determination of pantoprazole in human plasma using omeprazole as internal standard (IS). The plasma sample (100 μL) was deproteined by precipitation with methanol. The supernatant was directly determined by LC using a Diamonsil C₁₈ ODS column and solution of 10 mM Na₂HPO₄ buffer (containing 0.01% H₃PO₄) and acetonitrile (68:32, v/v, pH = 6.8) as mobile phase with UV detector set at 288 nm. The retention time of IS and pantoprazole were 4.9 ± 0.2 and 5.6 ± 0.2 min, respectively. The method was validated with a linear range of 0.03–5.0 μg mL^?1 and the lowest limit of quantification was 0.03 μg mL^?1 for pantoprazole (r = 0.9999). The coefficient of variation for intra-day and inter-day accuracy and precision was less than 9.5%. The mean extraction recovery was 84.1%. Quality control samples were stable when kept at autosampler temperature for 24 h, at ?20 °C for 42 days and after three freeze-thaw cycles. The assay was successfully applied to a randomized, two-period cross-over bioequivalence study in 20 healthy Chinese volunteers following a single oral dose of 40 mg pantoprazole. Various pharmacokinetic parameters including AUC _0～t , AUC _0～∞, C _max, T _max and t _1/2 were determined from plasma concentration of both formulations. The results indicated that the analytical method was a specific, precise, sensitive and rapid procedure for determination of plasma pantoprazole concentration and therefore, a suitable and valuable tool in the investigation of the clinical pharmacokinetics and bioequivalence.     

Computer simulation of the collision frequency of two particles in optical tweezers

Optical tweezers have been successfully used in the study of colloid science. In most applications people are concerned with the behaviour of a single particle held in the optical tweezers. Recently, the ability of the optical tweezers to simultaneously hold two particles has been used to determine the stability ratio of colloidal dispersion. This new development stimulates the efforts to explore the characteristics of a two-particle system in the optical tweezers.An infinite spherical potential well has been used to estimate the collision frequency for two particles in the optical trap based on a Monte Carlo simulation. In this article, a more reasonable harmonic potential, commonly accepted for the optical tweezers, is adopted in a Monte Carlo simulation of the collision frequency. The effect of hydrodynamic interaction of particles in the trap is also considered. The simulation results based on this improved model show quantitatively that the collision frequency drops down sharply at first and then decreases slowly as the distance between the two particles increases. The simulation also shows how the collision frequency is related to the stiffness of the optical tweezers.     

Compact continuous-wave blue lasers by direct frequency doubling of laser diodes with periodically poled lithium niobate waveguide crystals

A compact continuous-wave blue laser has been demonstrated by direct frequency doubling of a laser diode with a periodically poled lithium niobate (PPLN) waveguide crystal. The optimum PPLN temperature is near 28 degrees C, and the dependence of waveguide crystals on crystal temperature is less sensitive than that of bulk crystals. A total of 14.8 mW of 488-nm laser power has been achieved.