Relighting behaviour among cigarette smokers seeking treatment: implications for tobacco treatment and policy.

AIMS: During the recent economic downturn, trends towards fewer cigarettes smoked per day have emerged along with the practice of extinguishing and relighting cigarettes. Few studies have characterised factors related to relighting cigarettes and none have explored this behaviour in those seeking tobacco treatment. This study describes treatment-seeking patients who relight cigarettes and examines implications on tobacco policy and treatment. METHODS: Data were collected from a cross-sectional sample of 496 patients at a specialty tobacco treatment programme in New Jersey from 2010 to 2012. RESULTS: Forty-six per cent of the sample reported relighting, and those subjects smoked significantly fewer cigarettes per day (CPD), despite similar levels of dependence and exhaled carbon monoxide (CO) values. In unadjusted analyses, significantly higher rates of relighting were found among females, African-Americans, smokers who had a high school diploma or less, and were unemployed, sick or disabled. Relighting was more prevalent among smokers with higher markers of dependence, menthol smoking and night smoking. In multivariate analyses, markers of dependence and economic factors (employment and education) remained significant. CONCLUSIONS: Characteristics linked to economic factors were related to increased relighting. Implications for tobacco treatment include the impact on pharmacotherapy dosing and counselling interventions. The tobacco control community needs to be aware of this phenomenon. Collecting data on 'smoking sessions per day' might be a more accurate depiction of smoking exposure than CPD.

Spring filling of xylem vessels in wild grapevine.

Xylem vessels in grapevines Vitis labrusca L. and Vitis riparia Michx. growing in New England contained air over winter and yet filled with xylem sap and recovered their maximum hydraulic conductance during the month before leaf expansion in late May. During this period root pressures between 10 and 100 kilopascals were measured. Although some air in vessels apparently dissolved in ascending xylem sap, results indicated that some is pushed out of vessels and then out of the vine. Air in the vessel network distal to advancing xylem sap was compressed at about 3 kilopascals; independent measurements indicated this was sufficient to push air across vessel ends, and from vessels to the exterior through dead vine tips, inflorescence scars, and points on the bark. Once wetted, vessel ends previously air-permeable at 3 kilopascals remained sealed against air at pressures up to 2 and 3 megapascals. Permeability at 3 kilopascals was restored by dehydrating vines below -2.4 megapascals. We suggest that the decrease in permeability with hydration is due to formation of water films across pores in intervascular pit membranes; this water seal can maintain a pressure difference of roughly 2 megapascals, and prevents cavitation by aspirated air at xylem pressures less negative than -2.4 megapascals.

Direct and indirect measurements of Phloem turgor pressure in white ash.

Direct determinations and indirect calculations of phloem turgor pressure were compared in white ash (Fraxinus americana L.). Direct measurements of trunk phloem turgor were made using a modified Hammel-type phloem needle connected to a pressure transducer. Turgor at the site of the direct measurements was calculated from the osmotic potential of the phloem sap and from the water potential of the xylem. It was assumed that the water potentials of the phloem and xylem were close to equilibrium at any one trunk location, at least under certain conditions. The water potential of the xylem was determined from the osmotic potential of xylem sap and from the xylem tension of previously bagged leaves, measured with a pressure chamber. The xylem tension of bagged leaves on a branch adjacent to the site of the direct measurements was considered equivalent to the xylem tension of the trunk at that point. While both the direct and indirect measurements of phloem turgor showed clear diurnal changes, the directly measured pressures were consistently lower than the calculated values. It is not clear at present whether the discrepancy between the two values lies primarily in the calculated or in the measured pressures, and thus, the results from both methods as described here must be regarded as estimates of true phloem turgor.

Translocation velocity and specific mass transfer in the sieve tubes of Fraxinus americana L.

The ratios of sugar concentrations (sucrose/stachyose, raffinose/stachyose and sucrose/raffinose) in the sieve-tube exudate of Fraxinus americana L. undergo slight diurnal fluctuations. These "ratio waves" have been found to move down along the stem of trees at a velocity of 30-70 cm/h. They are, in contrast to the "concentration waves" of HUBER et al. (1937), independent of the absolute exudate concentration and thus unaffected by hydrodynamic pressures changes in the xylem. The velocity is of the order of magnitude required by the mass transfer equation and thus indicates that sieve tube exudate is a moving solution. Furthermore, the phenomenon enabled us for the first time to follow phloem transport over distances of 12 meters.

Analysis of complex vascular systems in plants: optical shuttle method.

The "optical shuttle" is an improved method of photographing with a motion-picture camera, one by one, sequential sections mounted on separate slides. The optical output from two microscopes is combined so that the images can be focused on a single film plane. Slides are photographed alternately through the microscopes. Simultaneous viewing of two successive sections in the microscopes enables initial precise alignment of images. Complex anatomical structures can thus be analyzed with relative ease.