鲨鱼软骨血管形成抑制因子的分离纯化及其活性的初步研究

以广东阳江鲨鱼软骨为原料,研究了鲨鱼软骨新生血管形成抑制因子的分离纯化方法,并对其生物学活性进行了初步研究.采用盐酸胍抽提、膜超滤、丙酮分级沉淀、SephadexG-75柱层析和C₄反相高效液相色谱等步骤,分离纯化出一种新的鲨鱼软骨血管生成抑制因子-a(SharkCartilageAngiogenesisInhibitor-a,SCAI-a),分子量为12600,能显著抑制鸡胚绒毛尿囊膜血管的形成.     

Magnetic nanotips: the realisation of an atomic-scale beam-splitter

We present the first realisation of ferromagnetic Fe nanotips. Studies of the field emitted beams of electrons and metallic ions above and under the Curie temperature T_c were made. We have observed a reversible splitting of the electron beams when the temperature crossed through T_c and multiple spot patterns for the emitted metallic ion beams. These phenomena were not observed with Fe microtips or non-magnetic nanotips and thus were correlated to a strong magnetic interaction at the atomic scale apex of the nanotips. The Fe nanotips constitute an atomic scale beam-splitter.     

Temperature-calibrated fiber-optic refractometer based on acompact FBG-SMS structure

A novel all-fiber temperature-calibrated refractometer based on a compact fiber Bragg grating(FBG) single-multi-single(SMS)structure is proposed and experimentally demonstrated.The sensor head is composed of a FBG combined with a SMS structure,in which the middle multimode fiber(MMF)section is etched by a time-controlled hydrofluoric.The transmission dip of SMS is extremely sensitive to ambient refractive index(RI)variation,whereas the upstream FBG provides the necessary temperature information for RI calibration.All aforementioned functions are performed via a compact FBG-SMS structure not longer than 25 mm.The proposed sensing device provides a linear RI sensitivity over water or waterbased solutions(RI values near 1.33 at optical wavelengths for most biological and many environmental applications),and has temperature-calibration capability.Hence,the said refractometer is a good candidate for sensing in chemical and biological applications.     

On Roussel–Rubio-type lemmas and their consequences

Roussel and Rubio proved a lemma which is essential in the proof of the Strong Perfect Graph Theorem. We give a new short proof of the main case of this lemma. In this note, we also give a short proof of Hayward’s decomposition theorem for weakly chordal graphs, relying on a Roussel–Rubio-type lemma. We recall how Roussel–Rubio-type lemmas yield very short proofs of the existence of even pairs in weakly chordal graphs and Meyniel graphs.     

Lattice dynamics of Eu<Subscript>1-x</Subscript>Y<Subscript>x</Subscript>MnO<Subscript>3</Subscript> (0 ≤ x ≤ 0.5)

A systematic and detailed study of Raman and infrared active lattice excitations in the orthorhombic multiferroic manganite Eu_1−xY_xMnO₃ (0 ≤ x ≤ 0.5) was carried out at room temperature. For the infrared active phonon modes the eigenfrequencies, damping constants and oscillator strengths were analyzed by Fourier-Transform Infrared Spectroscopy in the far infrared frequency range. For the Raman active phonons the same analysis for eigenfrequencies and damping constants was carried out using Raman spectroscopy in the range from 200 cm⁻¹ to 700 cm⁻¹. Y doping leads to mode-dependent phonon frequency shifts up to 8%. These are interpreted in terms of the interplay between the decrease of the reduced ion masses and the axis-dependent change of bond lengths. The latter leads to a bond softening along the a-axis and a strengthening along the c-axis, for which the highest phonon frequency increase is observed. The application of both Raman and Infrared Spectroscopy gives us sensitivity not only to symmetry properties via the selection rules but also to the involvement of different ion types within the unit cell. It is clearly shown that the disorder induced effects are of minor impact on the lattice properties and solely detected on the rare earth sites. The MnO₆ octahedra remain unaffected and show the same behavior as in the stochiometric RMnO₃ making Eu_1−xY_xMnO₃ an excellent model system for a quasi-continuous fine-tuning of the lattice parameters relevant for the appearance of multiferroicity.     

Tuning of nanotube mechanical resonances by electric field pulling

We show here that field emission (FE) can be used to directly observe the vibration resonances nu(R) of carbon nanotubes (CNTs) and that the tension created by the applied field allows the tuning of these resonances by up to a factor of 10. The resonances are observable by the changes they create in the FE pattern or the emitted FE current. The tuning is shown to be linear in voltage and to follow from the basic physics of stretched strings. The method allows one to study the mechanical properties of individual multiwall carbon nanotubes within an ensemble and follow their evolution as the CNTs are modified. The tuning and detection should be useful for nanometric resonant devices.     

Analysis of short-pulse laser photon transport through tissues for optical tomography

We describe a method for analyzing short-pulse laser propagation through tissues for the detection of tumors and inhomogeneities in tissues with the goal of developing a time-resolved optical tomography system. Traditional methods for analyzing photon transport in tissues usually involve the parabolic or diffusion approximation, which implies infinite speed of propagation of the optical signal. To overcome such limitations we calculate the transmitted and reflected intensity distributions, using the damped-wave hyperbolic P(1) and the discrete-ordinates methods, for a wide range of laser, tissue, and tumor parameters. The results are compared with the parabolic diffusion P(1) approximation.     

Detection and study of Rb I Rydberg states

We describe the details of an experiment using an atomic beam of rubidium which allowed us to detect by field ionization techniques the np Rydberg states from n = 28 up to n = 78, to detect also ns and nd states using a Stark mixing, and for all of these detected states to check the classical law E_c = [16n^*4]^?1 concerning the critical ionizing electric field E_c. It turns out that for n as high as 65 this law is quite well verified.     

Measurement of the spectral distribution of a multi-mode dye laser light by using speckle patterns

A simple method of measuring the wavelength γ₁ and the spectral line spacing Δγ of a multi-mode dye laser light by using the correlated speckle patterns produced at the far-field of a diffuser is proposed. Examples of the obtained values of γ₁ and Δγ are 6.0 × 10³ Å and 3.0 × 10¹ Å, respectively.