Arsenic and heavy metal contamination of rice, pulses and vegetables grown in Samta village, Bangladesh

Arsenic contaminated water from tube wells has become the major health problem threatening millions of people in Bangladesh. However, the arsenic (As) contaminated water is not just used for drinking, it is used to irrigate crops, and to wash and prepare food. Contamination of agricultural soils by long-term irrigation with As contaminated water can lead to contamination and phyto-accumulation of the food crops with As and other toxic metals. As a consequence, dietary exposure to As and other toxic metals may contribute substantially to the adverse health effects caused by the contaminated tube wells in Bangladesh. Various vegetables, rice, pulses and the grass pea were sampled in Samta village in the Jessore district of Bangladesh and screened for As, Cd, Cu, Pb and Zn by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. These local food crops provide the majority of the nutritional intake of the people in this area and are of great importance to their overall health. In general, our data show the potential for some vegetables to accumulate heavy metals with concentrations of Pb greater than Cd. The concentrations of As and Cd were higher in vegetables than in rice and pulses. The concentration of Pb was generally higher in rice than in pulses and vegetables. However, some vegetables such as bottle ground leaf, ghotkol, taro, eddoe and elephant foot had much higher concentrations of Pb. Other leafy and root vegetables contained higher concentrations oJ2n and Cu. Rice grown at Samta had increased Pb and As, but, considering an average daily intake of only 260 g rice per person per day, only the Pb is at concentrations which would be a health hazard/or human consumption.

The relationship between phase and period responses to light pulses

Current theories of stable circadian entrainment postulate phase delays should be associated with period lengthening, while phase advances should be associated with period shortening. While characterising features of the rat PRC to light, we noted substantial numbers of responses that displayed the opposite pattern. Forty-eight rats provided data for 192 phase responses. Limiting our analysis to phase shifts greater than 1 hour, we found 44 displayed the expected predicted relationship, and 33 displayed the contrary paradoxical relationship. Paradoxical responders possessed significantly shorter initial activity periods, compared to predicted responders. Activity was significantly lengthened by paradoxical responders and shortened by predicted responders following light pulse exposure. These results suggest a second mode of stable entrainment. Additionally, these results indicate entrainment mode, predicted or paradoxical, is based upon activity period duration. Short activity period durations will be associated with paradoxical responses, long durations will be associated with predicted responses. We argue that, given the dynamic changes in photoperiod, both modes of entrainment are necessary to provide stable entrainment across the year.

The effect of repeated pulses of light at the same time on period responses of the rat circadian pacemaker.

A consequence of simple velocity-based models is that, in response to light pulses, the circadian period should adjust inversely to phase. In addition, because of the interaction of circadian period and phase response, earlier circadian period changes should modify later circadian period changes. The literature contains few mentions of response curves of circadian period responses following light pulses. Rats were exposed to four pulses of light (60 minutes, 1000 lux) at the same circadian time, a minimum of 26 days apart; we assessed period responses and possible bias in the period-response curve. Modulation of circadian period following light-induced phase responses was examined by assessing the period of running wheel activity onset. Phase and circadian period were not consistently found to share an inverse relationship. Moreover, biases in initial period tended to be increased by the experimental protocol regardless of circadian time of pulse. Rats with a short initial (highvelocity) period had a lengthened period, while rats with a long initial period (low velocity) tended to have a reduce period. However, rats with a long initial period were phase delay biased, not phase advance biased. These results do not support a simple velocity model of the pacemaker.

On the electrochemical response and interfacial properties of steel–Ca(OH)2 and the steel–concrete system measured using galvanostatic pulses

The interfacial properties of the steel–concrete system are examined via a new approach for evaluation of galvanostatic pulse data. This methodology allows for rapid determination of the corrosion activity of steel, and readily yields values for parameters related to corrosion such as the polarisation resistance and interfacial capacitance. The method of analysis is based on the iterative fitting of a non-exponential model based on a modified Kohlrausch–Williams–Watt (KWW) formalism. The transient behaviour of steel in concrete is non-exponential in its form and, when analysed this way, an exponent β can be determined characterising the exponential non-ideality of the transient. This non-ideality parameter is found to differ significantly for actively corroding and passive specimens, thereby serving as a useful index to the level of corrosion being experienced. Furthermore, the investigation of the interfacial characteristics of the system, previously unobtainable in a reproducible manner via other electrochemical methods, reveal information regarding the kinetic factors governing corrosion of steel in concrete.