Visualizing the effect of gold nanocages on absorption, imaging, and lower critical solution temperature phase transition of individual poly(NiPAM)-based hydrogel particles by near infrared multispectral imaging microscopy

We have successfully utilized the near-infrared multispectral imaging (NIR-MSI) microscope to observe and measure directly images and spectra of individual hydrogel particles alone or with added gold nanocages (GNs). The NIR-MSI is suited for this task because it can simultaneously record spectral and spatial information of a sample with high sensitivity (single pixel resolution) and high spatial resolution (～0.9 μm/pixel). Because both images and spectra of the individual particles can be directly and simultaneously measured by the microscope, it is possible to detect any changes in the spectroscopic properties and/or nature (size, volume) of individual hydrogel particles induced by external factors (e.g., temperature and/or pH). These features make it possible to determine lower critical solution temperature (LCST) values based on monitoring either changes in the NIR spectra or the volume of the hydrogel particle in response to variations in temperature. More importantly, the measured volume transition temperature or LCST value is not of a collection of many hydrogel particles, but rather of individual hydrogel particles. GNs were found to significantly affect not only absorption but also images and properties of individual hydrogel particles. Specifically, GNs were found to enhance absorption of individual hydrogel particles, particularly the C-H band at 1716 nm, by about 25%. Of particular interest is the fact that not all individual hydrogel particles were enhanced by GNs; only about 50% of total number of particles were enhanced by GNs. GNs were also found to make it difficult to observe individual hydrogel particles, i.e., it seems that GNs defocused images of hydrogel particles. The defocusing effect by GNs might be due to photothermal generation of heat and vapor bubbles by the GNs. Of particular interest is the effect of GNs on the volume transition temperature of individual hydrogel particles. It seems that individual hydrogel particles lose their LCST in the presence of GNs, i.e., when heated, they undergo a gradual decrease in the volume but do not exhibit any clear and observable discontinued phase transition temperature.     

Mid-infrared luminescence properties of Dy-doped silver halide crystals

The absorption and the kinetics of the emission in the mid-infrared (mid-IR) were investigated in AgCl(x)Br(1-x) crystals doped with Dy(3+) ions. Strong emission bands were detected at 3, 4.4, and 5.5 μm and attributed to the (6)H(13/2)→(6)H(15/2), (6)H(11/2)→(6)H(13/2), and (6)F(11/2)+(6)H(9/2)→(6)H(11/2) transitions. Various optical parameters were calculated for the Dy(3+) doped crystals, using the Judd-Ofelt approximation and the rate equations. The measured results and the calculated parameters indicate that these doped crystals could be used for the development of mid-IR solid-state lasers or mid-IR fiber lasers.     

Dynamic contact problem for an absolutely rigid plate joined to a rigid slab on an elastic half space

The dynamic contact problem is solved by a method based on use of static determination of the stresses beneath a plate and additional slab. The static mixed edge problem is reduced to the solution of integral equations, and then to determination of the normal stresses on the contact boundary. A sample calculation confirms the effectiveness of reducting vibration by joining slabs to the basic foundation. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 2–6, September–October, 1995.     

Is it Possible to Analyze DNA and Protein Sequences by the Methods of Digital Signal Processing?

Informational content of linear macromolecules (DNA, RNA, and proteins) is analyzed by the method of digital signal processing. Each element (amino acid or nucleotide) of macromolecules is represented by the corresponding value of electron-ion interaction potential. This numerical representation of the primary structure of macromolecules is subjected to digital signal processing in order to extract the information corresponding to biological function. It is shown that the multiple cross spectrum of functionally related sequences exhibits significant peak frequencies. In the case of functionally unrelated sequences such peaks were not found. Peak frequencies are different for different biological functions. Based on this, we conjecture that the peak frequencies in the multiple cross spectrum of sequences with the same boilogical function are related to this biological function.     

Structure of cokes from coking coal vitrites

The coking process of vitrites and thermobitumens separated from vitrites was examined; structural X-ray and microscopic examinations of the cokes obtained were carried out. A correlation between reflectance distribution of vitrites and microscopic structure of their cokes was found.An increase in the structural ordering of the cokes from vitrites, passing from cokes of gas coal to cokes of orthocoking coals, is observed. It is accompanied by an increase of the optical anisotropy of the resultant cokes; this anisotropy first appears in coke from gas-coaking coal.The cokes from the thermobitumens are lower ordered than the cokes from parent vitrites but all these cokes are partially or entirely optically anisotropic.Total removal of the thermobitumens from coals deprives the cokes from the residues after the extraction of any optical anisotropy.     

Fluorometric method for determination of vitamin B6 in soya bean

Summary The simple fluorometric method for determination of added pyridoxine-HCl in enriched food, based on oxidation of pyridoxine to 4-pyridoxic acid by means of KMnO₄, has been modified for determination of total B₆ in soya bean. In comparison to the other fluorometric procedures, the proposed method is the simplest one, rapid and easy to perform, demanding the least time for oxidation and not using hazardous chemicals (KMnO₄ instead of KCN). Good recovery, low relative standard deviation and low total error allow the proposed procedure to be included into the group of excellent methods.

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Die fluorometrische Methode zur Vitamin B₆-Bestimmung in Soja

Zusammenfassung Die einfache fluorometrische Methode zur Bestimmung von zugegebenem Pyridoxin in angereicherten Lebensmitteln basiert auf der Oxidation des Pyridoxins mit Kaliumpermanganat zur 4-Pyridoxinsäure und wurde für die Bestimmung des gesamten Vitamin B₆ in Soja modifiziert. Im Vergleich mit anderen fluorometrischen Methoden ist die vorgeschlagene, einfach, schnell und leicht durchzuführen. Diese Methode braucht nur wenig Zeit für die Oxidation und verwendet ungiftige Chemikalien (KMnO₄ statt KCN). Die gute Wiederfindung, die geringe relative Standardabweichung und der geringe Gesamtfehler reiht das vorgeschlagene Verfahren in die Gruppe der ausgezeichneten Methoden ein.

     

Utilization of organic phosphates by selected bacteria and algae

Studies showed that synthetic phosphates of a surface active nature may become a source of carbon and energy for the Bacillus licheniformis. Bacillus mycoides, Bacillus cougulans and Azotobacter agilis bacteria in spite of the fact they are hardly oxidizable. In addition, it was found that these compounds may also become a source of phosphorus for the Scenedesmus obliquus alga which proves that these algae contain suitable phosphatases permitting utilization of a specific organic compound.