Chi recombination activity in phage lambda decays as a function of genetic distance

In Escherichia coli, chi is a recombination hotspot that stimulates RecBCD-dependent exchange at and to one side of itself. chi activity is highest at chi and decreases with distance from chi. The decrease in chi activity may be a simple property of the physical distance over which chi can stimulate recombination. Alternatively, the decay in chi activity with distance may reflect the high likelihood that chi-stimulated recombination occurs in a single chi-proximal act, to the exclusion of additional chi-stimulated exchanges more distal to chi. To test the models, we determined if chi activity decreases as a function of physical distance (i.e., DNA base pairs) or genetic distance (homologous DNA base pairs). Our results indicate that chi activity decays as a function of genetic distance. In addition, we found that the sbcB gene product (exonuclease I, a 3'-->5' ssDNA exonuclease) modulates the distance over which chi can act. In contrast, the recJ gene product (a 5'-->3' ssDNA exonuclease) does not alter the decay of chi activity.     

Comparison of the resistance of C57BL/6 and C3H/He mice to infection with Mycobacterium paratuberculosis

Susceptibility of C57BL/6 (Bcgs) and C3H/HeN (Bcgr) mice to an intraperitoneal infection with Mycobacterium paratuberculosis strain 19698 was compared (by histopathology and the number of mycobacteria isolated from the spleen). Mycobacterial counts from the spleen of Bcgr mice progressively decreased over the course of infection but remained unchanged in Bcgs mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcgs mice, whereas lesions were transient or absent in Bcgr mice. These results indicate that Bcgr mice are inherently resistant to M. paratuberculosis, whereas Bcgs mice are inherently susceptible. These differences may prove useful in elucidating the mechanisms of resistance and susceptibility to paratuberculosis and other mycobacterial infections.     

Intrathecal opioids provide satisfactory conditions in labor analgesia and spinal anesthesia for cesarean section

Metastases is an uncommon cause of tumors in the sinonasal region. We report a patient with hepatocellular carcinoma which metastasized to the nasal cavity.     

Effect of nutrient seed coating on the emergence of wheat and oats

A series of experiments was conducted under controlled soil moisture and temperature conditions in a growth chamber to examine the effect of a range of nutrient seed coatings on the emergence to wheat (Triticum aestivum L. cv. Kite) and oats (Avena sativa L. cv. Blackbutt) sown in a coarse sandy loam soil. Final emergence of oats was not reduced by a coating containing 10 kg P ha^–1 (as monocalcium phosphate [MCP]) whereas the same coating reduced wheat emergence by 15%. The emergence of both wheat and oats was severely reduced by urea coatings (supplying 10 kg N ha^–1) to 33 and 13% respectively; this injury was lessened markedly by the inclusion of phenyl phosphorodiamidate (PPD) in the urea coatings at 1% (w/w) (emergence increased to 66 and 56% respectively).Low soil moisture (67% of field capacity [FC]) resulted in almost no emergence of wheat coated with urea (± bentonites of different pH). In soil at FC, the addition of bentonite of pH 5 (B5) to urea coatings permitted greater emergence (54%) than when bentonite of pH 9 (B9) was added (32%) which, in turn, permitted greater emergence than urea coating alone (10%). When PPD and bentonite (B5 or B9) were combined either singly or together with urea in seed coatings, PPD was more effective than either of the bentonites in reducing injury and masked the slight positive effect of B5.Coatings containing various combinations of N and P sources (at 3.6 and at 8 kg ha^–1 respectively) all reduced the emergence of wheat compared to raw seed (91% emergence). When applied alone, MCP was least damaging (74%); the combination of MCP with ammonium sulfate (AS) caused somewhat more injury (68%) whilst combination with calcium nitrate (CN) caused most injury (29%). In contrast, CN alone caused relatively little damage (73%) whilst AS alone was more damaging (50%). There was no significant regression found between percentage emergence and either the calculated partial salt index or the pH of the nutrient coatings. Further work is needed to examine the mechanisms of injury due to nutrient seed coatings so that safe but effective formulations can be developed.     

Measurement of O2-N2 binary sorption on 5A zeolite by isotope tracer and perturbation chromatography

Isotope tracer chromatography allows to extract simply and quickly multi component adsorption data and is demonstrated for single component and binary adsorption equilibria for O₂ and N₂ on 5A zeolite as an example. In this modification of conventional tracer chromatography, a small pulse of an isotope tracer is injected in an adsorbable carrier gas (pure or multicomponent mixture) flowing through a column filled with adsorbent and is designed to operate at almost uniform pressure. Isotherm parameters are readily extracted by fitting measurements of residence times at various pressures and carrier composition. The isotherms were in excellent agreement with volumetric measurements. Isotope tracer chromatography is shown to be superior to perturbation chromatography since the influence of the injection volume on the carrier gas composition is substantially smaller for tracer experiments. Unfortunately, this new improved gas chromatographic technique requires rather expensive isotopes. The strength of this new approach lies in the advantage of working with small adsorbent samples (1 g) making a rapid screening of newly developed materials possible.Nomenclature K _exp,tr,i experimental tracer adsorption constant (mol/kg pure adsorbent/Pa) - K _i Henry adsorption equilibrium constant (mol/kg pure adsorbent/Pa) - K _i,part partition coefficient - K _pert composite Henry constant (mol/kg pure adsorbent/Pa) - L column length (m) - L _i Langmuir adsorption constant (1/Pa) - n _i amount adsorbed on the solid (mol/kg adsorbent) - N _i adsorbent loading (Pa) - p total pressure (Pa) - p _i partial pressure of component i (Pa) - p _in column inlet pressure (Pa) - p _out column outlet pressure (Pa) - q _i amount of component i in the micropores (Pa) - R gas constant (J/mol/K) - t time (s) - T temperature (K) - v _f superficial velocity in adsorbent column (m/s) - v _out velocity at the outlet of the column (m/s) - V _inlet volumetric flow rate at inlet conditions (ml/s) - x molar fraction of tracer - y molar fraction of component i in the carrier gas - z axial coordinate (m) Greek letters _ext bed voidage, external porosity - _macr macropore porosity [_macr= _p (1–_ext)] - _micr micropore porosity - _tot total porosity - _p pellet porosity - volume fraction of binder material - _d dead time (s) - _tracer tracer residence time (s) - _pert perturbation residence time (s) - _crys crystal density (kg/m³)     

Examination of the relationship between cracking resistance,hardness, and strength of steels at different temperatures and strain rates

The results are presented of measurements of Brinell hardness HB of 15Kh2NMFA and 10G2FB steels in the temperature range 77 T 373K. The resultant HB values are compared with strength, impact toughness, and cracking resistance in the entire temperature range examined. The relationship between cold brittleness of the steels and the form of the HB-T curves is analyzed on the basis of the concept of the characteristic temperature of contact deformation. The results show that the relationship between hardness and yield limit depends in a complicated manner on the test temperature and is determined by the plastic deformation mechanisms operating in each individual case. Correlation dependences are presented for determining the height of the stretching zone and stress intensity factor on the basis of HB values at different temperatures and strain rates. A criterion K_Ic/HB is introduced to predict the cracking resistance inside the examined temperature range on the basis of the values of K_Ic and HB at the boundaries of this range.Translated from Problemy Prochnosti, No. 2, pp. 14–17, February, 1991.     

Investigations of development process of high hollow beveled microneedles using a combination of ICP RIE and dicing saw

Micromachined needles provide a promising technology for painless delivery of molecules or foreign substance into a living cell. Over the recent years, a variety of different microneedle shapes and materials have been studied and have shown their facility to disrupt stratum corneum layer to increase the skin permeability. In this paper, we described an alternative process to fabricate high and beveled hollow out-of-plane microneedles. Silicon microneedles dimensions are 40–60 μm in inner diameter, 150–200 μm in outer diameter and over 700 μm in height. Tip angles reached are from 30° to 45°.