Microscopical examinations, modified

Solid PDA have not had an extensive reaction chemistry largely due to their van der Watds tight-packed structures which effectively preclude diffusion of potentially reactive liquids and gases (. Recently (17), reactions of poly-DCH (2c) with electrophiles have led to modified materials which are homogeneous on microscopic examination. The reactions are anisotropic. Bromination resulted in a crystal-to-crystal transformation, while chlorination and nitration have led to amorphous solids to date. The scope of such reactivity is clearly of interest. 

Recently, we observed that the PDA from l,6-di-N-carbazolyl-2,4-hexadiyne (2a), i.e., poly-DCH (2), reacts with assorted gaseous and liquid species to give modified materials which appear homogeneous on microscopic examination (1). Our studies to date of the interaction of chlorine, bromine, and iodine with single crystals of poly-DCH are presented herein. 

To observe the movements of the biopolymers into and retention in the vegetable cells, the biopolymers were modified into colored compounds suitable for use as markers in microscopic examinations. The biopolymers were reacted with Remazol brilliant blue R salt according to Rinderknecht et al. (32) with modifications. The reaction created covalent bonds between the blue dye and hydroxyl groups of the biopolymers. The dye-biopolymyer complexes have the same physical properties as natural biopolymers. These types of dyes have been used for cellulose materials (33) and galacto-D-Mannan (34). 

Based on the encouraging results obtained in these simulated flow studies, knitted polyester patches were subjected to the same modification with rHir (42). Segments with covalently boimd rHir and control (BSA-treated) polyester patches were implanted in the thoracic aortas of canines and exposed to non-heparinized aortic blood flow for two hours. The materials were explanted and the loss of rHir was found to be 20%. The remaining antithrombin activity was assessed explanted patches were able to inhibit 7 NIHU of thrombin. Gross and microscopic examination of the explanted patches showed that the controls had a thick surface acellular layer (pseudointima) composed of fibrin rich thrombus, while the rHir modified patches had no gross thrombus, and a thin pseudointima of platelets and plasma proteins (Figure 4). 

We have recently initiated our investigation of blends by examining the compatibility between our modified polymer sample 4 and poly(methyl methacrylate). Mixtures with a composition of between 10% and 30% of sample 4 yield compatible blends which are transparent under a polarized light microscope, and are characterized by a single Tg. Mixtures richer than 60% of 4 undergo complete phase separation. 

Armed with this new tool, Schena et al. (1996) created a microarray of 1,046 human cDNAs of unknown sequence. They were derived from human peripheral blood lymphocyfes fransformed wifh Epsfein-Barr virus. Suitably sized inserts [>600 base pairs (bp)] were cloned into a lambda vector, subsequently infected into an Escherichia coli strain, and finally amplified by polymerase chain reaction (PCR) using 5 -amino-modified primers. The resulting 5 -amino-modified cDNA amplicons were then arrayed onto sily-lated microscope slides. Next, the expression levels in human Jurkat cells undergoing heat shock or phorbol ester induction were examined. 

SEM) Microscopies. Methods to prepare specimens for microscopic studies developed by Mollenhauer and Totten (33) and modified by Cegla et al. (30) were followed. TLM examinations were conducted on a Zeiss Standard 19 Research microscope. TEM examinations were conducted on a Hitachi HS-8 at Kv on 600-800A sections prepared according to Galey and Nilsson (34). SEM examinations were conducted on JOEL JSM-35 at 25 kv. 

When examined with a scanning electron microscope, none of the exposed chemically modified celluloses exhibited any significant changes in morphology beyond the appearance of fractured fiber ends and fibrillar cracks. Such damage was also detected in the exposed nonoxidized control. 

Scanning electrochemical microscopy (SECM the same abbreviation is also used for the device, i.e., the microscope) is often compared (and sometimes confused) with scanning tunneling microscopy (STM), which was pioneered by Binning and Rohrer in the early 1980s [1]. While both techniques make use of a mobile conductive microprobe, their principles and capabilities are totally different. The most widely used SECM probes are micrometer-sized ampero-metric ultramicroelectrodes (UMEs), which were introduced by Wightman and co-workers 1980 [2]. They are suitable for quantitative electrochemical experiments, and the well-developed theory is available for data analysis. Several groups employed small and mobile electrochemical probes to make measurements within the diffusion layer [3], to examine and modify electrode surfaces [4, 5], However, the SECM technique, as we know it, only became possible after the introduction of the feedback concept [6, 7],... 

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