chemotaxis of rhizobium phaseoli towards flavones and other related compounds

The formation of nitrogen-fixing nodules on leguminous plants is the result of a highly specific interaction between the host plant and the soil bacterium Rhizobium. Two observations suggest that chemotaxis may play a role in the establishment of the legume-Rhizobium symbiosis: 1) The widespread occurence of Rhizobium species with flagella (Gotz, 1982; Carlile. 1980)2) The copious exudation into the soil surrounding legume roots of a wide variety of potentially chemotactic compounds which include amino acids, sugars and sugar-acids. (Beringer et.al.,1979). Recently the plant flavones luteolin (3,44,7 - Tetra - hydroxyflavone) and apigenin (4,5,7 - Trihydroxy-flavone) have been reported as inducers of Rhizobium nodulation genes (Peters, 1986, Rolfe 1986). We report here that R. phaseoli (RP8002) exhibits positive chemotaxis toward both flavones. Other diverse compounds tested elicited different responses. An understanding of the influence of flavones in two events such as chemotaxis and nodulation efficiency can be valuable to clarify their action in the intricate legume-rhizobia interaction

Exits from unemployment: recall or new job

This paper studies transitions out of unemployment in Spain distinguishing between recall to the same employer and reemployment in a new job. We use a large sample of newly unemployed workers obtained from Social Security records for Spain. These data contain information about each individual's employer identy before and after the unemployment spell. A discrete-time duration model with competing risks of exits serves us to investigate the factors that influence the probabilities of leaving unemployment to return to the same employer or to find a new job with a different employer. We find that the route to exit unemployment is determinant to understand the influence of individual an job characteristics on the hazard rate, as well as the latter dependence on unemployment duration. The recall hazard rate exhibits positive duration dependence during the first months and negative duration dependence thereafter (it is larger for females), while the new-job hazard presents positive duration dependence (it is larger for males).

Does downsizing improve organizational performance? An analysis of Spanish manufacturing firms

The objective of this study is to examine the effect of downsizing on corporate performance, considering a sample of manufacturing firms drawn from the Spanish Survey of Business Strategies during the 1993- 2005 period. No significant differences in post-downsizing performance arise between companies which downsize and those that do not. Likewise, we find that substantial workforce reductions through collective dismissals do not either lead to improved performance levels. Downsizing, therefore, may not be a way for managers to increase performance, particularly in a context like the Spanish one, where the labour market is characterized by a high protection of employees’ rights and substantial contract termination costs.Downsizing, Corporate performance, Spanish labour market

Downsizing implementation and financial performance

In the present study we explore the relationship between downsizing decisions and corporate financial performance after top management has decided to downsize. Our focus is on the financial consequences arising from the amount of downsizing and the use of disengagement incentives. For this purpose, we use a sample of downsizing announcements in the Spanish press from 1995 up to 2001. Although the results show that the amount of downsizing is not significantly related to post-downsizing profitability, the evidence provided supports the finding that the use of disengagement incentives (which motivate workers to leave the organization) is negatively related to firm performance. Our analysis helps to understand the role that strategic downsizing decisions play in explaining observed variance in the performance of downsized firms. Thus, it advances scholarly organizational research by reinforcing the concept that corporate performance is not only contingent on strategies, but also influenced by the means through which these strategies are implemented.Downsizing, Disengagement incentives, Corporate performance, Spanish labour market

Tangential projections and secant defective varieties

Going one step further in Zak's classification of Scorza varieties with secant defect equal to one, we characterize the Veronese embedding of $\P^n$ given by the complete linear system of quadrics and its smooth projections from a point as the only smooth irreducible complex and non-degenerate projective subvarieties of $\P^N$ that can be projected isomorphically into $\P^{2n}$ when $N\geq\binom{n+2}{2}-2$.Comment: To appear in Bulletin of the London Mathematical Societ

Effects of Vibration Training on Reducing Risk of Falls among Young Adults with Obesity

Obesity is a major concern around the world. One of the major concerns associated with obesity is that it leads to increased risk of falls. High risk of falls among obese individuals has been related to several factors such as abnormal body mass distribution, muscle weakness, and postural instability. A significant portion of obese individuals are unable or unwilling to comply or manage conventional training regimens requiring high intensity and long duration. Therefore, alternative training methods are in high demand. Controlled whole-body vibration (CWBV) training has been proven to reduce the risk of falls among older adults. No study has yet investigated the potential effect of CWBV training on reducing falls among obese populations. The purpose of this study was to systematically examine the overall effectiveness and feasibility of CWBV training in reducing the risk of falls among individuals with obesity. Particular interest was placed in studying the impact of 6-week CWBV training on reducing body fat percentage, improving muscular strength, and enhancing dynamic gait stability. The institutional Review Board approved all procedures and subjects provided written consent. Five young healthy adults (age: 26.2 ± 9.04 years; height: 172.16 ± 4.43 cm; mass: 100.18 ± 6.28 kg; 2 females) with obesity participated in the experiment. Obesity was determined based on the body mass index (BMI ≥ 30 kg/m2) and body fat percentage ≥30%. All subjects received CWBV training 3 days a week for 6 weeks. A vibration platform was used to administer the training in an intermittent way: each 1-minute vibration was followed by a 1-minute rest for 10 minutes when subjects stood on the platform. The vibration frequency was 25 Hz and the amplitude 7.8 mm. Prior to and following the 6-week training, subjects were evaluated for their risk of falls quantified in terms of body fat percentage, muscle strength, and dynamic gait stability. The body fat percentage was measured by a bioelectrical impedance analysis machine. Maximum knee extensor strength under isometric condition was assessed via an isokinetic dynamometer at right side. The dynamic gait stability was computed, at both touchdown (TD) and liftoff (LO) within a gait cycle, from the full body kinematics gathered by a motion capture system. Paired t-test results indicated that the body fat percentage did not vary between the two evaluations (37.45% ± 7.40% vs 37.45% ± 7.65%, p \u3e 0.05). However, the knee extensor strength increased from 1.66 ± 0.28 Nm/kg in pre-training evaluation to 1.83 ± 0.23 Nm/kg in the post-training evaluation (p \u3c 0.05). Subjects were more stable during the post-training test than in the pre-training one. At TD (LO), the dynamic stability increased to 0.70 ± 0.05 (0.40 ± 0.03) post training from 0.61 ± 0.02 (0.32 ± 0.06) prior to the training (p \u3c 0.01 for TD and p \u3c 0.05 for LO)