No abstract

Osteoporosis is recognized as an important cause of morbidity and mortality in aging women, but there have been few epidemiologic studies in men. Potential risk factors for osteoporotic fractures were assessed in 220 elderly men aged 60 years or above in the city of Dubbo (Australia). During the follow-up period of 1989-1994, the overall incidence of fractures (determined from x-ray reports) was 220 fractures per 10,000 person-years. Higher risk of fracture was associated with lower femoral neck bone mineral density (BMD), quadriceps weakness, higher body sway, falls in the preceding 12 months, a history of fractures in the previous 5 years, lower body weight, and shorter current height. Use of thiazide diuretics, higher physical activity, and moderate alcohol intake were protective against fracture. In multivariate analysis (Cox's proportional hazards model), femoral neck BMD (odd ratio (OR) = 1.47, 95% confidence interval (CI) 1.25-1.73 per 0.12 g/cm2), quadriceps strength (OR = 1.43, 95% CI 1.18-1.73 per 10 kg), and body sway (OR = 1.25, 95% CI 1.07-1.45 per 5.15 cm2) were independent risk factors. Preventive measures for bone loss and maintaining a physically active, healthy life-style and modification of risk factors for falls in the elderly could yield beneficial effects in the reduction of the incidence of osteoporotic fracture and hence improve the survival among men.

No abstract

Excessive levels of heavy metals in water are an environmental hazard. An Australian zeolite with (ICZ) and without (Z) iron-coating, was used to remove five heavy metals from aqueous solutions using adsorption in batch and column experiments. The batch study showed that the Langmuir adsorption capacities of heavy metals on Z and ICZ at pH 6.5 and ionic strength 10-3 M NaNO 3 were in the order Pb > Cu > Cd > Cr, Zn for single metal (5.0-11.2 mg/g) and for mixed metals solution (3.7-7.6 mg/g). The data for the kinetics of adsorption satisfactory fitted to both the pseudo-first and second order models with fits slightly better for the latter model. Data fitted to a diffusion model revealed that adsorption took place in two or more than two different stages: a fast external surface adsorption, and a gradual adsorption controlled by both film diffusion and intra-particle diffusion. The column adsorption data were fairly well described by Thomas model, with the order of Thomas adsorption capacity following a similar trend as in the batch study. In both batch and column experiments, the adsorption capacities were higher for ICZ than for Z and were generally lower in mixed metals system than in single metals system. Leaching of used ICZ columns with 0.1 M HCl, resulted in 64-93% of adsorbed metals being desorbed, and 10% of Fe being dissolved from the ICZ.

An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl -, NO3 -, SO4 2-, and CO3 2-) provide a high anion exchange capacity (53-520 meq/100g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorptioncoupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and (2) the types of interlayer anions (i.e., guest intercalated organic anions). The low Brunauer-Emmett-Teller specific surface area of LDH (1.80-179 m 2 /g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Q o max) toward Cr(VI) was significantly affected by the used inorganic salt natures and synthetic methods of LDH. The Q o max values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (∆G° <0) and endothermically (∆H° >0) and increase the randomness (∆S° >0) in the system. Thus LDH has much potential as a material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater.