Synthesis, characterization, and thermal stability of poly(N-maleyl glycine-co-N-vinylpyrrolidone)

The free radical copolymerization of N-maleyl glycine (MG) with vinylpyrrolidone (NVP) was studied in the range from 10 to 90 mol% in the feed. Copolymer compositions obtained by elemental analysis reflect the monomer feed concentrations. The r₁ and r₂ were determined by the Fineman-Ross and Kelen-Tüdos method. The experimental data indicate random comonomer incorporation with slightly alternating tendency. The thermogravimetric analysis of the copolymers showed high thermal stability in N₂. Received: 24 March 1997/Revised: 10 June 1997/Accepted: 18 June 1997     

Intraparenchymatous vascular tumors of the testicle: report of a new case of cavernous hemangioma

The occurrence of a vascular tumour at the intraparenchymatous testicular level is a fact little reported in the literature. Searching for such events, 19 cases were found all of which showed benign clinical behaviour. The most commonly seen histological pattern is cavernous haemangioma (11 patients). Mean age at presentation is 19 years old and the most usual pre-operative diagnosis, germinal cell neoplasia. Since there are no specific ultrasound patterns that may allow to differentiate benign from malignant masses, inguinal orchiectomy is the choice treatment in this type of lesions. Furthermore, the case of a 44-year old patient with hypoechogenic solid mass in left testis who consulted for sporadic episodes of long-standing scrotal pain is presented. After radical exeresis of the gonad, the histological analysis showed existence of testicular cavernous haemangioma.     

Inactivity changed fiber type proportion and capillary supply in cat muscle

The proliferative activity of the rat corpus luteum was studied on days 2, 3, 6, 9, 12, 15, 17, 19 and 21 of pregnancy. Proliferating cells were detected by the immunohistochemical demonstration of DNA-incorporated 5-bromodeoxyuridine (BrdU) and by the presence of mitoses. Steroidogenic luteal cells showed two proliferative waves on days 12-15 and on day 21, when relatively abundant BrdU-labeled and mitotic cells were observed. These cells were clearly distinguishable from non-steroidogenic cells by their round nuclei and large polygonal cytoplasm. The proliferative activity on days 12-15 was coincident with an increase in the size of the cells and in progesterone concentrations. On the other hand, the proliferative activity of non-steroidogenic luteal cells (especially endothelial cells of the blood and lymphatic vessels) followed a different pattern. These cells intensely proliferated on days 2-3 of pregnancy and this proliferative activity was significantly higher than that observed in non-pregnant rats on metestrus and diestrus. A new proliferative wave was observed on days 12-15, in association with the increase in the proliferative activity of steroidogenic cells. The presence of both BrdU-labeled and mitotic steroidogenic luteal cells provides evidence that these cells do proliferate and that both hypertrophy and hyperplasia are involved in the increase in the parenchyma of the corpus luteum during pregnancy. Also, the results suggest that different mechanisms are involved in the regulation of the proliferative activity in the corpus luteum at different times during pregnancy.     

Weak and strong basic resins for uranium recovery

Summary Resins were synthesized by crosslinking of linear polyethyleneimine and subsequent N-methylation. The retention properties of these resins, for copper (pH=0 to 4); for uranium (pH=0 to 3) and for iron (pH=0 to 2) were studied. The maximum capacity of adsorption for uranium and the elution of uranium with sulphuric acid and sodium carbonate were determined. The resins, in general, do not retain iron. The thermal stability was also studied.     

A contribution to the measurement of permittivity with theshort-circuited line method

The elimination of the ambiguity in the short-circuited line method for determining the dielectric permittivity by measuring the change in the position of the minimum for two similar frequencies is studied. This quantity is used to uniquely determine the coefficients of an algebraic equation with a single physical solution. Ambiguity may or may not be removed depending on the dielectric characteristics of the sample and on the value of the ratio sample thickness/wavelength. The former are not known a priori and the latter is an experimental parameter, which can be varied. The influence of this parameter on the elimination of ambiguity is studied. Finally the analysis is compared to results of measurements on several organic liquids     

Polyethyleneimine supports for resins with retention properties for heavy metals part I

Summary Resins with retention properties for copper (II), and uranium (VI) have been synthesized by crosslinking of polyethyleneimine with 1,4-dibromo-2-butene and subsequent alkylation with dimethyl sulphate. The influence of pH on the retention, maximum capacity of load and elution assays were determined.     

Poly(acrylic acid‐co‐vinylsulfonic acid): Synthesis,characterization, and properties as polychelatogen

The synthesis of the water‐soluble poly(acrylic acid‐co‐vinylsulfonic acid) at different feed monomer ratios, while maintaining constant the total number of mol, was carried out by radical polymerization. The copolymers were characterized by FTIR and ¹H‐NMR spectroscopies. The copolymer composition was determined by its sulfur content and by potentiometric titration. The metal ion binding properties for Ni(II) and Cu(II) in the aqueous phase were studied using the liquid‐phase polymer‐based retention (LPR) technique for two values of ionic strength. For comparison, the retention properties of both homopolymers were included. The complexing ability of the polymer was determined by the relative amount of carboxylic acid groups. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1698–1704, 2003     

Method to interpolate induced current with low amount of sample points by means of Bezier surfaces

A new interpolation technique to represent the induced current with a very low amount of sample points and computational cost is presented. The amplitude and phase of the current are represented separately, each one being defined at any point of the scattering surface by an interpolating function, built using Bezier's surfaces.     

Diffusion barrier cladding in Si/SiGe resonant interband tunneling diodes and their patterned growth on PMOS source/drain regions

Si/SiGe resonant interband tunnel diodes (RITDs) employing /spl delta/-doping spikes that demonstrate negative differential resistance (NDR) at room temperature are presented. Efforts have focused on improving the tunnel diode peak-to-valley current ratio (PVCR) figure-of-merit, as well as addressing issues of manufacturability and CMOS integration. Thin SiGe layers sandwiching the B /spl delta/-doping spike used to suppress B out-diffusion are discussed. A room-temperature PVCR of 3.6 was measured with a peak current density of 0.3 kA/cm/sup 2/. Results clearly show that by introducing SiGe layers to clad the B /spl delta/-doping layer, B diffusion is suppressed during post-growth annealing, which raises the thermal budget. A higher RTA temperature appears to be more effective in reducing defects and results in a lower valley current and higher PVCR. RITDs grown by selective area molecular beam epitaxy (MBE) have been realized inside of low-temperature oxide openings, with performance comparable with RITDs grown on bulk substrates.     

Necrotizing enterocolitis in horses: a retrospective study

OBJECTIVE: To evaluate awareness and knowledge of cigarette filter ventilation in a national probability sample of smokers of Ultra-light, Light, and regular cigarettes. DESIGN: Random-digit-dialling and computer-assisted telephone interviewing was used on a probability sample of daily cigarette smokers (ages 18 and above). SUBJECTS AND SETTING: 218 Smokers of Ultra-light cigarettes, 360 smokers of Light cigarettes, and 210 smokers of Regular cigarettes living in the continental United States. MAIN OUTCOME MEASURES: Percentage of respondents indicating knowledge of the presence of filter vents and the consequences of behavioural blocking of vents. RESULTS: Many smokers had not heard about or seen the filter holes: 43% (95% CI = 36 to 50%) of smokers of Ultra-lights, 39% (95% CI = 34 to 44%) of smokers of Lights, and 47% (95% CI = 40 to 54%) of smokers of Regulars. About two in three smokers either did not know of the existence of rings of small holes on the filters of some cigarettes, or did not know that blocking increases tar yields: 69% (95% CI = 63 to 75%) of Ultra-lights, 66% (95% CI = 61 to 71%) of Lights, and 69% (95% CI = 63 to 75%) of Regulars. CONCLUSIONS: Smokers are generally unaware of the presence and function of filter vents-a major design feature subject to behavioural blocking by smokers and now present on most cigarettes in the United States. Smokers and policy-makers need to be informed about the presence of filter vents and how vent blocking increases tar and nicotine yields from ostensibly very low-yield cigarettes.