Search

The vacancy production behavior for a broad range of incident ion-target combinations were examined by using both the full cascade (F-C) and quick calculation of damage (Q-C) options of Stopping and Range of Ions in Matter (SRIM-2013) code. Vacancy production for each option was evaluated using both the convenient vacancy text file in SRIM, and by manual manipulation of the energy transfer, ionization, and phonon text file data to calculate the depth-dependent damage energy for the Norgett-Robinson-Torrens (NRT) defect production model. The F-C vacancy text file method was observed to overpredict vacancy production by a factor of ~1.1 to 4 times when compared to values calculated using the F-C damage energy method or either of the SRIM Q-C methods. Based on our extensive data set obtained for 142 unique bombarding ion-target combinations, we show that the SRIM F-C vacancy text file method should not be used for vacancy production calculations. This error appears to be due to mischaracterization within the SRIM F-C option of some near-threshold replacement events as vacancies instead of replacements. Use of the latest SRIM stopping powers in the SRIM F-C approach provides a better calculation of electronic and nuclear stopping compared to the Lindhard stopping power analytical approximation used to calculate the damage energy of recoil atoms in the SRIM Q-C option, and therefore SRIM F-C approach is deemed to provide the best accuracy for vacancy production (within the binary collision approximation) as long as the damage energy method is used. Alternately, the SRIM Q-C option using either the vacancy.txt or damage energy method provides relatively fast calculation speeds with moderate quantitative differences from the F-C damage energy results (~0 to ~ 30% for the investigated ion-target cases).

International audience; Herein, we demonstrate that tuning of structural parameters and material chemistry enables control of the permeability and selectivity of gases (CO2, He, and CH4) in membranes based on poly(butyl methacrylate)-grafted nanoparticles (PGNs). Our data show that the presence of nanoparticles and the overall dense packing of grafted chains noticeable in PGNs with low grafting density have an adverse effect on the diffusivity of gases. This effect is compensated by an improvement in the solubility of CO2 gas promoted by the silica nanoparticle surface, yielding a substantial improvement in the permeability of CO2 versus CH4. In membranes with high grafting density, changes in the structural arrangements and alterations in the membrane porosity, evident from small-angle X-ray scattering and positron annihilation lifetime spectroscopy, positively influence the permeability of He and CO2 gases. In contrast, CH4 permeability in the same membranes is significantly suppressed, suggesting the formation of a unique, highly selective environment for gas separation. As a result, an improvement of up to 50% in selectivity for gas pairs containing large CH4 molecules is observed. Our studies provide fundamental insights into the role that structural parameters play in gas transport through polymer membranes, laying a foundation for the rational design of membranes with improved permeability and selectivity.

Ketosis is a common metabolic disorder in high-producing dairy cows during the peripartal period. Negative energy balance leads to increased circulating levels of nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHB), consequently increasing the risk of ketosis. It is well-known that NEFA and BHB can induce lipotoxicity and oxidative stress in bovine tissues/organs including the liver and adipose tissue. Although the mammary gland is one important site for NEFA and BHB metabolism, whether an overload in their concentrations within mammary cells causes oxidative stress during ketosis remains unclear. Thus, the present study compared oxidative stress status and mitochondrial function in mammary tissues harvested by biopsy from healthy (n = 15) and clinically ketotic (n = 15) dairy cows within 2 to 3 wk postpartum. Compared with healthy cows, ketotic cows had depressed daily milk yield (median: 28.92 vs. 21.56 kg) and dry matter intake (median: 22.36 vs. 19.92 kg/d), accompanied by elevated plasma NEFA (median: 0.32 vs. 1.26 mM), BHB (median: 0.52 vs. 3.69 mM), and lower plasma glucose (median: 4.55 vs. 2.13 mM). As detected by a commercial kit, a greater level of reactive oxygen species in mammary epithelial cells of ketotic cows, and greater oxidant indices including hydrogen peroxide and malondialdehyde coupled with lower antioxidant indices including glutathione peroxidase, catalase, and superoxide dismutase activities as detected by the respective biochemical kits in the homogenate of mammary tissue of ketotic cows indicated increased oxidative stress status. Lower citrate synthase activity and ATP production as detected by the respective commercial kits coupled with lower mRNA and protein abundance of mitochondrial respiratory chain oxidative phosphorylation complexes I-V (CO I-V) in ketotic cows suggested an impairment of mitochondrial function. This was supported by lower mRNA and protein abundance of nucleus-derived mitochondrial function regulators including peroxisome proliferator activated receptor gamma coactivator 1 α, mitofusin 2, nuclear respiratory factor 1, and mitochondrial transcription factor A. Lower mitochondrial membrane potential evaluated via the tetraethylbenzimidazolylcarbocyanine iodide (JC-1) labeling method and swollen mitochondria in mammary epithelial cells of ketotic cows suggested the existence of mitochondrial damage. Overall, the present study revealed extensive mitochondrial dysfunction and oxidative stress in the mammary gland of clinically ketotic cows. As such, data suggest that reduced milk yield in cows with ketosis is partly due to enhanced oxidative stress along with mitochondrial dysregulation in the mammary gland.

Low temperature-sintered ceramics Nd2Zr3(MoO4)9 were successfully prepared via reaction-sintering method. The sintering behavior, microwave dielectric properties, crystal structure, and microstructure were analyzed systematically. XRD and Rietveld refinement results revealed that all samples formed a pure trigonal structure phase with the space group of R-3c. Density determination showed that ceramics possessed the highest relative density when sintered at 800 °C for 6 h. SEM image further confirmed that ceramics possessed dense and homogeneous microstructure at the optimum sintering temperature 800 °C. Far infrared spectra analysis showed the structural phonon oscillation at infrared region played an important role in polarization. Nd2Zr3(MoO4)9 ceramics obtained the optimum microwave dielectric properties of er= 10.01, Q × f = 55,923 GHz, τf= − 13.81 ppm/ °C when sintered at 800 °C for 6 h.

Subclinical ketosis (SCK) in dairy cows, a common metabolic disorder during the peripartal period, is accompanied by systemic inflammation. Excessive release of azurophil granule (AG) contents during degranulation of polymorphonuclear neutrophils (PMN) could contribute to systemic inflammation in SCK cows. Although the increase in blood free fatty acids (FFA) in SCK cows may promote AG degranulation from PMN, the underlying mechanisms are unclear. Thirty multiparous cows (within 3 wk postpartum) with similar lactation numbers (median = 3, range = 2-4) and days in milk (median = 6, range = 3-15) were classified based on serum β-hydroxybutyrate (BHB) level as control (n = 15, BHB0.6 mM) or SCK (n = 15, 1.2 mMBHB3.0 mM). Cows with SCK had greater levels of serum haptoglobin, serum amyloid A, IL-1β, IL-6, IL-8 and tumor necrosis factor-α. These proinflammatory factors had strong positive correlations with myeloperoxidase (MPO), a marker protein of PMN AG, whose content was greater in the serum of SCK cows. Both the number of AG and the protein abundance of MPO were lower in PMN isolated from SCK cows. Additionally, we found a greater ratio of blood CH138A

Single-phase concentrated solid solution alloys (SP-CSAs) are newly emerging advanced structural materials, which are defined as multiprincipal element solid solutions. SP-CSAs with more than four components in equimolar or near-equimolar ratios are also referred to as high-entropy alloys due to their high configurational entropy. SP-CSAs are potential structural materials in advanced nuclear energy systems due to their attractive mechanical properties. Therefore many investigations have been carried out to study the irradiation-induced structural damage and defect behavior in SP-CSAs. This paper reviews recent experimental results on the irradiation responses of various SP-CSAs, focusing on the accumulation of irradiation-induced structural damage, void swelling resistance, and solute segregation behavior. In addition, the characteristic defect behavior in SP-CSAs derived from ab initio and molecular dynamics simulations, as well as the challenges in the applications of SP-CSAs for the nuclear energy systems are briefly discussed.

Structural damage and chemical segregation in Al0.1CoCrFeNi high entropy alloy irradiated at elevated temperatures are studied using transmission electron microscopy (TEM) and atom probe tomography (APT). Irradiation-induced defects include dislocation loops, long dislocations and stacking-fault tetrahedra, but no voids can be observed. As irradiation temperature increases, defect density is decreased but defect size is increased, which is induced by increasing defect mobility. APT characterization reveals that ion irradiation at elevated temperatures can induce an enrichment of Ni and Co as well as a depletion of Fe and Cr at defect clusters, mainly including dislocation loops and long dislocations.

Sapphire should be highly transparent for photon energies less than the band gap, but residual, weak absorption and scattering losses in the near infrared occur as a result of extrinsic and intrinsic defects. Lattice disorder, impurities, and point defects have all been implicated as being the origin of loss phenomena but very little experimental evidence exists to quantitatively establish the relationships that might exist between these defects and optical loss. In this study, three synthetic, c-axis sapphire samples manufactured under similar conditions were characterized using UV-VIS spectroscopy, photothermal common-path interferometry, and positron annihilation lifetime spectroscopy. Model-based interpretation of optical measurements indicated that vacancy-type defects were partially responsible for absorption loss from the ultraviolet to the near-infrared and that the population densities differed among the samples. Positron annihilation lifetime spectroscopy measurements also indicated a higher concentration of cationic vacancy defects near the sample surface which correlates with a higher surface optical loss. This work establishes the use of positron annihilation techniques as a characterization tool for optical materials that could be useful for investigating the origin of weak surface absorption in the transparent region of sapphire.

We report on density functional theory calculations that have been performed to systematically investigate the hydrogen-surface interaction as a function of surface orientation. The interactions that were analyzed include stable atomic adsorption sites, molecular hydrogen dissociation and absorption energies, migration pathways and barriers on tungsten surfaces, and the saturation coverage limits on the (1 1 1) surface. Stable hydrogen adsorption sites were found for all surfaces. For the reconstructed W(1 0 0), there are two primary adsorption sites: namely, the long-bridge and short-bridge sites. The threefold hollow site (3F) was found to be the most stable for W(1 1 0), while the bond-centered site between the first and second layer was found to be most stable for the W(1 1 1) surface. No bound adsorption sites for H2 molecules were found for the W surfaces. Hydrogen (H) migration on both the (1 0 0) and (1 1 0) surfaces is found to have preferred pathways for 1D motion, whereas the smallest migration barrier for net migration of H on the W(1 1 1) surface leads to 2D migration. Although weaker H interactions are predicted for the W(1 1 1) surface compared to the (1 0 0) or (1 1 0) surfaces, we observe higher H surface concentrations of Θ = 4.0 at zero K, possibly due to the corrugated surface structure. These results provide insight into H adsorption, surface saturation coverage and migration mechanisms necessary to describe the evolution from the dilute limit to concentrated coverages of H.

The change detection of high-resolution remote sensing images has always been a research difficulty and hot spot, which has a great application demand in land use change and ecological environment monitoring. U-type neural network can train a better model with less samples, and has good experimental effect in medical image segmentation, but it is rarely used in remote sensing image change detection research. In this paper, the U-type neural network is used to detect the change spots in GF-1 image of Yuzhou City, Henan Province, and compared with FCN, SegNet and Siamese-CNN. Experimental results show that the F1 score of U-type neural network model are 0.699 and 0.66 respectively, which are better than the other three methods, and the omission is lower, which is closer to the label map. Therefore, it is feasible to use U-type neural network for change detection of high-resolution remote sensing images, and it can have high detection accuracy.

Tungsten (W) has been perceived as one of the most promising plasma facing materials (PFMs) for future fusion reactors. In the past decade, its behavior under irradiation and helium (He) plasma interaction has been extensively studied. However, some key knowledge gaps still exist, such as the influence of crystallographic orientation on the surface and subsurface evolutions. In this work, we focus on the He ion-beam irradiation damage effects in mirror-polished single-crystalline W samples with three different surface planes of {100}, {110} and {111}. Irradiation was performed at room temperature using 40 keV He+ to a fluence of 1 × 1016/cm2, followed by thermal desorption spectroscopy (TDS) up to ~1920 K. The microstructures of He-irradiated W before and after TDS heat treatment were characterized by scanning and transmission electron microscopy. Subsurface He bubbles were imaged in all irradiated samples, but newly formed -oriented surface grains and surface blisters were only observed in W {100} and {110} starting orientations. These results reveal that radiation damage, He thermal desorption, and surface/subsurface evolution are all strongly dependent on crystallographic orientation. Underlying physical mechanisms are discussed based on ion channeling effects, He-vacancy interactions, and surface diffusion. These findings provide new insights into He effects in W.

In recent years, high entropy alloys (HEAs) have attracted significant attention due to their excellent mechanical properties and good corrosion resistance, making them potential candidates for high temperature fission and fusion structural applications. However there is very little known about their radiation resistance, particularly at elevated temperatures relevant for energy applications. In the present study, a single phase (face centered cubic) concentrated solid solution alloy of composition 27%Fe-28%Ni-27%Mn-18%Cr was irradiated with 3 or 5.8 MeV Ni ions at temperatures ranging from room temperature to 700 °C and midrange doses from 0.03 to 10 displacements per atom (dpa). Transmission electron microscopy (TEM), scanning transmission electron microscopy with energy dispersive x-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterize the radiation defects and microstructural changes. Irradiation at higher temperatures showed evidence of relatively sluggish solute diffusion with limited solute depletion or enrichment at grain boundaries. The main microstructural feature at all temperatures was high-density small dislocation loops. Voids were not observed at any irradiation condition. Nano-indentation tests on specimens irradiated at room temperature showed a rapid increase in hardness ∼35% and ∼80% higher than the unirradiated value at 0.03 and 0.3 dpa midrange doses, respectively. The irradiation-induced hardening was less pronounced for 500 °C irradiations (

Low dose neutron irradiation has been conducted on a NiFeMnCr (Co-free) high entropy alloy (HEA) near room temperature. Post-irradiation examination (PIE) at room temperature revealed that this HEA exhibited qualitatively similar change in mechanical properties (hardness, strength and ductility) as conventional austenitic stainless steels. Isochronal annealing was performed to determine the hardness, electrical resistivity and defect property evolution with respect to annealing temperature. Different annealing behavior was observed. Irradiation hardening nearly completely anneals by 650 °C, although the annealing trend is different following exposure to 0.1 and 1 displacements per atom (dpa). Positron Annihilation Spectroscopy (PAS) measurements indicate that the temperature to initialize vacancy cluster (stage V) recovery is ∼400 °C, and that the density of vacancy-type defects is reduced to that of the unirradiated control specimen at 500 °C. No significant change in the chemical ordering near defects was measured by PAS after neutron irradiation or after isochronal annealing up to 700 °C. Electrical resistivity measurements revealed a large increase in resistivity following irradiation, and this resistivity increase does not significantly recover even after the 700 °C anneal. Overall, these annealing results indicate the HEA vacancy cluster annealing behavior is similar to conventional face centered cubic (FCC) alloys whereas solute diffusion is limited up to 700 °C (significantly more sluggish than conventional FCC alloys). X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that this HEA exhibit good phase stability upon neutron irradiation up to 1 dpa and post-irradiation annealing up to 700 °C.

We report the results of ab initio calculations of a novel NiFeMnCr high entropy alloy (HEA) with potential applications as a high performance structural material. The bulk and defect property variations due to chemical disordering and magnetic frustration have been studied using both supercell and coherent potential approximation-based techniques. While magnetic frustration due to the presence of multiple 3d transition metals can severely affect the accuracy of vacancy formation energy in first-principles calculations, this effect should be suppressed at intermediate and high temperatures. An efficient approach to evaluate the chemical potential in HEA is constructed and implemented. Vacancy formation energies are computed based on the chemical potential. The statistical distribution of formation energies is weakly dependent upon the chemical identity of the vacancy. On the other hand, the calculated vacancy migration energies show that Fe is more likely to have a large migration barrier than Cr, Mn, or Ni. Finally, atomic-level stresses are computed. A qualitative model to explain the elemental segregation trend in HEA is built upon the atomic-level stress calculation results and provides a reasonable qualitative agreement with ion irradiation experimental data of a NiFeMnCr HEA.

Pressure-induced structural modifications in high-entropy alloys with varying Al contents, AlxCoCrFeNi (x = 0, 0.1, 0.3, 0.75, 1.5), have been investigated at pressures up to ∼50 GPa by synchrotron X-ray diffraction and, following depressurization, by transmission electron microscopy (TEM). In AlxCoCrFeNi compounds with x ≤ 0.3, all of which exhibit an initial single-phase face-centered cubic (fcc) structure, proportionality between the Al content and the critical pressure for transformation to hexagonal close-packed (hcp) phases, distinguished by a distinct planar stacking sequence, is observed. This is attributed to the structural distortion arising from the large size of Al atoms relative to those of the other constituent elements, which results in an increase in the formation energy of stacking faults and a decrease in compressibility. High-resolution TEM results demonstrate variation of the stacking sequence from ABCABC, typical of fcc materials, to ABABAB, typical of hcp materials, in CoCrFeNi following high pressure. In Al0.75CoCrFeNi, which exhibits an initial dual-phase structure [fcc and body-centered cubic (bcc)], the result again shows the formation of a (hcp) phase despite its higher Al content, suggesting that the bcc phase may be more amenable to pressure-induced phase modification than is the fcc phase, which is absent for lower Al contents. However, the trend of transformation inhibition by increasing the Al content is again observed, with Al1.5CoCrFeNi retaining its initial structure up to the highest pressure achieved. Determination of these compositional trends in the high-pressure phase response of these materials may enable the production of new phase mixtures with precisely tuned phase proportions and potentially desirable properties.

The LAMB1 gene encodes the laminin beta1 subunit of laminin, an extracellular matrix protein. Using several transgenic mouse lines containing various lengths of the LAMB1 promoter driving lacZ reporter gene expression, regions of LAMB1 promoter that contain cis-acting DNA regulatory element(s) have been identified. The 3.9LAMB1betagal transgene is expressed in various tissues during development. LAMB1 transgene expression is observed in a selective set of nephrons of the neonatal and adult kidneys. The cis-acting DNA regulatory elements responsible for LAMB1 transgene expression in ovaries and in juvenile kidneys are present between -'1.4 and -0.7 kb relative to the transcription start site, while those of adult kidneys are located between -2.5 and -1.4 kb. The LAMB1 transgene is also expressed in the epididymis of 1 week old transgenic mice. Mutation of the retinoic acid response element (RARE) in the context of the 3.9LAMB1betagal transgene results in loss of LAMB1 transgene expression in all tissues. Thus, sequences between -2.5 and -0.7 kb plus the RARE are required for appropriate expression of the LAMB1 transgene in mice.

Kidney-specific cadherin (Ksp-cadherin, cadherin 16) is a novel, kidney-specific member of the cadherin superfamily that is expressed exclusively in the basolateral membrane of renal tubular epithelial cells. To characterize the Ksp-cadherin gene promoter, a λ bacteriophage clone containing 3.7 kb of the proximal 5′ flanking region of the mouse Ksp-cadherin gene was isolated. The transcription initiation site was mapped by RNase protection assays and 5′ rapid amplification of cDNA ends, and a 709-bp intron was identified within the 5′ untranslated region. The proximal 5′ flanking region was “TATA-less” but contained other consensus promoter elements including an initiator (Inr), GC boxes, and a CAAT box. Potential binding sites were identified for transcription factors that are involved in tissue-specific gene expression including activator protein-2 (AP-2), hepatocyte nuclear factor-3 (HNF-3), basic helix-loop-helix (bHLH) proteins, CCAAT/enhancer-binding protein (C/EBP), and GATA factors. Transfection of luciferase reporter plasmids containing 2.6 kb of the 5′ flanking region markedly increased luciferase activity in renal epithelial cells (MDCK and mIMCD-3) but not in mesenchymal cells (NIH 3T3 and MMR1). Deletion analysis identified an 82-bp region from −31 to −113 that was essential for promoter activity in transfected renal epithelial cells. Electrophoretic mobility-shift assays showed that mIMCD-3 cells contain nuclear proteins that bind to this region of the promoter. Mutational analysis showed that sequences within the HNF-3 consensus site and CAAT box were involved in protein binding and promoter activity. We conclude that the proximal 5′ flanking region of the mouse Ksp-cadherin gene contains an orientation-dependent promoter that is kidney epithelial cell specific. The region of the promoter from −113 to −31 is required for transcriptional activity and contains binding sites for nuclear proteins that are specifically expressed in renal epithelial cells.

PURPOSE: To evaluate the agreement between intraocular pressure (IOP) readings measured by the Ocular Response Analyzer (ORA) and corrected Goldmann applanation tonometry (cGAT), derived from the "gold standard" for the clinical measurement of IOP, in eyes of subjects who have undergone laser in situ keratomileusis (LASIK). The effects of corneal biomechanical properties on IOP were also evaluated. METHODS: This was a retrospective cross-sectional study. The IOP of 148 eyes of 148 patients who have undergone LASIK was measured by the ORA and GAT one after another. cGAT was calculated according to a correction formula for IOP after LASIK. Central corneal thicknesses and corneal curvature (K value) were also measured. Corneal hysteresis and corneal resistance factor (CRF) were measured by the ORA. RESULTS: For the postoperative subjects, whose ages ranged from 18 to 37 years, the average IOP readings for GAT, cGAT, IOPg, IOPcc were 10.09 ± 2.43, 13.34 ± 2.52, 9.79 ± 2.52, 13.91 ± 2.26 mm Hg, respectively. The mean difference between IOPcc and cGAT was 0.63 ± 1.31 mm Hg (p

Escherichia coli lacks flagella when grown in tryptone broth in the presence of various adverse conditions (C. Li, C. J. Louise, W. Shi, and J. Adler, J. Bacteriol. 175:2229-2235, 1993). Now, the synthesis, rather than the degradation, of flagellin was shown to be inhibited. Studies of transcriptional fusions of flagellar operons to the lacZ gene revealed that transcription of the flagellar genes was reduced in cells grown under these adverse conditions. Increasing gene dosage of the flhD operon by a plasmid partially suppressed the nonflagellation caused by some adverse conditions. The signal which shuts off the synthesis of flagella under adverse conditions remains to be discovered. This shutting-off process does not result from catabolite repression or from signals from the chemotaxis system.

Wild-type Escherichia coli was not motile when grown in tryptone broth under the following adverse conditions: the presence of high temperature [J. Adler and B. Templeton, J. Gen. Microbiol. 46:175-184, 1967; R. B. Morrison and J. McCapra, Nature (London) 192:774-776, 1961; K. Ogiuti, Jpn. J. Exp. Med. 14:19-28, 1936], high concentrations of salts, high concentrations of carbohydrates, high concentrations of low-molecular-weight alcohols, or the pressure of gyrase inhibitors. Under all these conditions, growth was necessary for the loss of motility. This loss of motility was correlated with a reduction in the amount of cellular flagellin. We isolated and studied mutants that are resistant to suppression of motility by some of these conditions, because of the ability to synthesize flagella under these conditions. The mutations were mapped to 42 min, a region of the chromosome where many of the flagellar genes map. We also studied the effect of a preexisting gyrA mutation which allowed flagellar formation in the presence of nalidixate.

Retinoic acid (RA) and cyclic AMP analogs cause the differentiation of F9 embryonic teratocarcinoma stem cells into parietal endoderm, an epithelial cell of the early mouse embryo. Laminin B1 is induced in this differentiation process, but is not transcriptionally activated until 24-48 h after RA addition and is not maximally induced until approximately 72 h. Cyclic AMP analogs enhance this transcriptional activation. Although several DNase I hypersensitive sites (DHSS) were observed in the LAMB1 5 -flanking DNA, one of the sites, DHSS2, was detected only after 72 h of RA treatment. Transient transfections have demonstrated that the DHSS2 region functions as a "late-acting RA-inducible enhancer," and motifs in this enhancer contain the homeobox protein-binding site TTATTAACA. Greater binding is observed at these sites by electrophoretic mobility shift assay when cells are cultured with RA and cyclic AMP analogs versus RA alone, and no binding is seen in extracts from RA-treated F9 RAR gamma-/- cells which lack RAR gamma mRNA and protein. Laminin B1 mRNA is not induced by RA in the RAR gamma-/- cells (Boylan, J. F., Lohnes, D., Taneja, R., Chambon, P., and Gudas, L. J. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 9601-9605). Our data show that these DNA regulatory elements contribute to the transcriptional activation of the LAMB1 gene during the later stages of the differentiation process.

Behavioral responses to osmotic upshift were characterized by temporal assays of free-swimming cells of Escherichia coli. Small osmotic upshifts (200 to 300 mosM) elicited tumble responses which were chemotaxis dependent, while large osmotic upshifts (400 to 500 mosM) elicited stopping followed by pseudotumbling which was chemotaxis independent.

The escape of motile organisms from high concentrations of chemicals was studied in Escherichia coli. We have found all chemicals tested to be osmorepellents. It was shown in both a spatial assay and a temporal assay that the known sensory receptors for chemotaxis are not used for osmotaxis, so a different sensory mechanism appears to be employed. According to the temporal assay, the mechanism between sensory receptors and flagella is also not used for tumbling response (at least in solutions above 0.4 osmolar).