The use of ultrasound-stimulated acoustic emission in the monitoring of modulus changes with temperature

It has been previously shown that the amplitude of the ultrasound-stimulated acoustic emission (USAE) signal is sensitive to tissue temperature and, therefore, can help detect it. Its amplitude, however, is sensitive to both acoustical and mechanical parameters, that at most frequencies have opposite effects due to temperature. In this paper, we explore the feasibility of using a frequency shift of the resonant peaks of the USAE signal for monitoring the tissue stiffness variation with temperature. In a numerical simulation, the variation of the frequency shift at different temperatures is shown. Then, in a series of experiments involving a gel phantom and porcine muscle tissue, the frequency shift variation is shown to follow the known stiffness changes due to temperature. It is also shown that this shift indicates reversible changes as well as the onset of thermal coagulative necrosis. The necrosis is marked by a monotonically increasing positive frequency shift. It was thus shown that the USAE spectrum peaks undergo a negative shift (or, downshift) when the stiffness decreases and a positive shift (or, upshift) when the stiffness increases. The experimental frequency shifted around a peak at 22.1-22.5 kHz within a range of -250 to 80 Hz and -200 to 250 Hz for the gel and muscle tissue for the temperatures of 25-70 and 30-70 degrees C, respectively. Simulation and ex vivo experimental results indicate that the USAE frequency shift method can help decouple the mechanical from the acoustical parameter dependence as well as detect the onset of thermal coagulative necrosis.     

采用一锅法制备量子点/琼脂纳米复合凝胶

以天然高分子琼脂为稳定剂,采用简单便捷的一锅法制备Mn掺杂ZnS量子点/琼脂纳米复合凝胶,琼脂不仅作为制备量子点的稳定剂,同时也是纳米复合凝胶的主要成分。对该纳米复合凝胶中量子点的化学结构和尺寸大小进行了表征,并对纳米复合凝胶的荧光性能和凝胶性能进行了研究。实验结果表明,制备得到的纳米复合凝胶均一稳定,在302 nm紫外光下呈现十分明显的橙红色荧光。在该纳米复合凝胶的透射电子显微镜（TEM）表征中可以观察到大小比较均一、粒径为3 nm左右的纳米粒子,光谱分析结果进一步证实纳米复合凝胶中存在Mn掺杂ZnS量子点。该纳米复合凝胶不仅具有良好的荧光性能,还具有温度刺激响应性可逆溶胶-凝胶转变性能,同时具有较高的溶胶转变温度和较好的温度稳定性。利用这些性能特点,可以方便地制备纳米复合凝胶小球。此外,该纳米复合凝胶还可以被潜在应用于金属离子的荧光检测分析领域。     

Immobilization of Urease from Pigeonpea (<Emphasis Type="Italic">Cajanus cajan</Emphasis>) on Agar Tablets and Its Application in Urea Assay

The pigeonpea urease was immobilized on agar, a common gelling substance. The tablet strips were used as moulds to cast agar tablets of uniform shape and size. The time and temperature of solidification of agar was 6 min and 44 degrees C, respectively. The 5 % agar (w/v) and 0.019 mg protein/agar tablet yielded an optimum immobilization of 51.7%. The optimum pH was shifted through 0.2 U (from 7.3 to 7.5) towards basic side upon immobilization. The optimum temperature of soluble and immobilized urease was 30 degrees C and 60 degrees C, respectively, showing the improvement in thermal stability of urease. There was an increase in K m from 3.23 to 5.07 mM after immobilization. The half-lives of soluble and immobilized urease were 21 and 53 days, respectively, at pH 7.3 and 4 degrees C. The urea was estimated in different blood samples with the help of immobilized urease and the results were consistent with those from clinical pathology laboratory through an autoanalyzer (Zydus Co., Rome, Italy).     

琼脂微载体的制备及肝细胞附着生长情况的研究

以琼脂为原料,通过悬浮方法成球制备琼脂微载体,直径100～800μm.利用氨基化修饰琼脂微载体,比较大鼠肝细胞在其上的生长情况,并对培养的肝细胞的形态及葡萄糖、白蛋白的代谢情况进行了测定.     

Synthesis,characterization and anti-microbial activity of poly(ethylene oxamide- N,N ′-disuccinate) and its polymer metal complexes

Poly(ethylene oxamide-N,N′-disuccinate), abbreviated as (PEODS), has been synthesized by condensation of oxamide-N,N′-disuccinic acid and 1,2-ethylene glycol. Coordination polymers were synthesized by the reaction of (PEODS) with hydrated acetates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). The resulting polyester-metal complexes were characterized by elemental analysis, UV-Visible, FT-IR, ¹H-NMR, ESR spectroscopy and magnetic susceptibilities. Thermal behavior of all the synthesized compounds revealed that polymer metal complexes are more stable than the polymeric ligand. In addition all the synthesized polymers were screened for anti-bacterial activity against B. subtelillisr, B. megaterium, S. aureus, E. coli, S. typhi, P.?aeruginosa, S. boydii and for antifungal activity against C. albicans, T. species, A. flavus, A. niger, F. species, M. species, and P. species by agar well diffusion methods. All the polymers showed good anti-bacterial and anti-fungal activity, which increased on coordination with the metal ions.     

Synthesis and Study of Tercopolymers

Tercopolymers have been prepared by condensing a mixture of salicylic acid, thiourea, and any one of such comonomers as o-cresol, p-cresol, o-chlorophenol, and p-chlorophenol with trioxane in the presence of 2 M HCl as catalyst. The tercopolymers were characterized by elemental analyses. Their M[Mbar]_n was determined by nonaqueous conductometric titration both against standard sodium methoxide and tetra-n-butyl ammonium hydroxide and also by the VPO method. Also made were an IR spectral study, a viscometric study in dimethylformamide (DMF), and a thermal study based on TGA. Chelation ion-exchanging properties of selected tercopolymer samples were also studied by employing the batch equilibration method.     

Antimicrobial and Antimalarial Activity of Novel Synthetic Mononuclear Ruthenium(II) Compounds

The present work was aimed that the two Ruthenium compounds namely, [Ru(A)₂(B)]Cl₂, where A = 1,10‐phenanthroline; B = 2‐NO₂‐phenyl thiosemicarbazone (Compound R₁)/2‐OH‐phenyl thiosemicarbazone (Compound R₂) have been tested for antibacterial activity at the concentrations of 1 mg/mL against various Gram‐Positive organisms (Lactobacillus, Staphylococcus pyrogenes, Bacillus subtilis, Staphylococcus aureus & Bacillus megatarium) and Gram‐Negative organisms (Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris, Enterobacter aerogenes, Salmonella paratyphi, Klebsiella pneumonia & Proteus mirabilis). The compounds were also tested for antifungal activity against Aspergillus clavatus, Aspergillus niger, Colletotrichum & Penicillium notatum by using agar diffusion assay and antimalarial activity against Plasmodium falciparum (Strain 3D7) using MTT assay. The results concluded that the compound R₁ exhibited significant antibacterial activity than R₂ against Gram‐Negative bacteria with zones of inhibition ranging from 15‐20 mm. and mild antibacterial activity against Gram‐Positive bacteria in comparison to tetracycline, streptomycin and rifampicin. These complexes were found to have moderate antifungal activity with no activity was however observed against Aspergillus niger. The compound, R₁ exhibited antimalarial activity at 10 μg/mL, whereas R₂ did not show antimalarial activity upto 50 μg/mL. Sensitivity to the compounds was greatest in the gram‐negative bacteria, followed by the gram‐positive bacteria and fungi.     

New agar microspheres for the separation and purification of natural products

A new type of agar chromatography media has been prepared with a yield over 80% using a water‐in‐oil emulsion technique. These microspheres have regular spherical shapes and particle diameters in the range 40–165 μm (average ～90 μm). Cross‐linking of the resulting agar microspheres with epichlorohydrin and 1,4‐butanediol diglycidyl ether enhanced their mechanical and thermal stability. The alkaline conditions used during the cross‐linking reaction also decreased the content of ionized sulfate groups of the polysaccharide, thus reducing the nonspecific adsorption of positively charged molecules. The cross‐linked agar microspheres were functionalized with (i) branched poly(ethyleneimine) to obtain a stationary phase useful for the separation of proteins in an anion‐exchange mode and (ii) with poly‐β‐cyclodextrin enabling direct isolation and purification of puerarin from a crude extract of Radix puerariae. Using a 23.5 mL column loaded with 20 mg extract (0.85 mg/mL gel), puerarin with a purity of 96% was recovered with a yield of 86%.     

Characterization of Polyene Sequences in Poly(vinyl Chloride)

Some aspects of the formation and propagation of polyene sequences during the thermal degradation of PVC have been discussed. The average polyene sequence length occurring in a suspension polymerized PVC, degraded in nitrogen at 190°C, was determined to ca. 10 units. The results were somewhat dependent on the type of analysis employed. The formation of internal polyene sequences was characterized by three stages. After an initial period, where the number of internal sites remained constant, new sites were rapidly formed. The high rate of formation then gradually decreased with increasing conversion. Degradation mechanisms explaining this behavior were suggested.     

琼脂固溶胶中的抗坏血酸在玻碳电极上的电化学行为

在玻碳电极上研究了 0.05 mol·L-1 Na2HPO4 0.05 mol·L-1 NaH2PO4 20.0 g·L-1琼脂固溶胶中抗坏血酸的电化学行为,并与 0. 05 mol·L-1 Na2HPO4 0. 05 mol·L-1NaH2PO4 溶液中的抗坏血酸在玻碳电极上的电化学行为进行了比较,对抗坏血酸的氧化产物用紫外光谱进行了鉴定。提出了一种用于研究电极反应机理及电化学合成有机化合物的新方法。