We conducted a case–control study to investigate factors associated with epidemic cholera. Water treatment and handwashing may have been protective, highlighting the need for personal hygiene for cholera prevention in contaminated urban environments. We also found a diverse diet, a possible proxy for improved nutrition, was protective against cholera.
Pewter, a tin-rich alloy, has been widely used for ornamental and utilitarian purposes for the last 400 years because it is durable, relatively easily worked, resistant to corrosion, and similar to silver in appearance. Pewter plates and implements have been recovered and examined from what is believed to be the wreck site of the Queen Anne's Revenge, flagship of the pirate Blackbeard, that sank near Beaufort, North Carolina in 1718. All of the pewter artifacts from the site display a surface veneer of corrosion products and may be viewed as experiments on tin corrosion that have been continuously in operation for more than 280 years. Mineralogical examination of the pewter samples has revealed that the corrosion products are composed of romarchite (SnO), hydroromarchite [Sn 3 O 2 (OH) 2 ], and abhurite [Sn 21 Cl 16 (OH) 14 O 6 ]. The corrosion generally develops in crudely concentric layers, with an inner layer of abhurite in contact with the pewter; the overlying outer layers consist of romarchite and hydroromarchite. Romarchite, hydroromarchite, and abhurite occur as irregular grains and laths up to 100 micrometers in length. Abhurite also occurs as masses of equant grains with abundant small inclusions of residual pewter. Thermodynamic considerations reveal that romarchite may be a metastable phase, and is present as the result of sluggish kinetics in the process of the formation of cassiterite (SnO 2 ), the most stable tin oxide in most natural environments. Observation and identification of these phases will be useful in understanding the stability of tin in the weathering environment and the nature of the metal's corrosion products.Keywords: romarchite, hydroromarchite, abhurite, tin oxide, pewter, corrosion, Queen Anne's Revenge, Blackbeard, metal artifacts, North Carolina. SOMMAIRE L'utilisation d'alliages d'étain a été répandu au cours des 400 dernières années dans les applications ornamentales et utilitaires à cause de leur durabilité, la facilité avec laquelle on peut les travailler, leur résistance à la corrosion, et leur ressemblance à l'argent. Des assiettes et des outils en étain ont été récupérés et examinés d'une épave qui serait celle du Queen Anne's Revenge, navire major du pirate Blackbeard, qui a fait naufrage près de Beaufort, en Caroline du Nord en 1718. Tous les artéfacts en étain provenant de ce site ont un placage de produits de corrosion; on peut ainsi les considérer comme témoins d'une expérience en corrosion de l'étain qui dure depuis plus de 280 ans. Un examen minéralogique de ces échantillons d'étain a révélé la nature de ces produits de corrosion: ils contiennent romarchite (SnO), hydroromarchite [Sn 3 O 2 (OH) 2 ], et abhurite [Sn 21 Cl 16 (OH) 14 O 6 ]. La corrosion se développe en général en couches à peu près concentriques, avec une couche interne d'abhurite en contact avec l'étain; les couches externes contiennent romarchite et hydroromarchite. Romarchite, hydroromarchite, et abhurite se présentent en grains irréguliers et en tablettes atteignant 100 m en longueur....
Assessing immunization system performance by using administrative data has notable limitations. In addition to long-term improvements in administrative data management, alternatives for measuring routine immunization performance should be considered.
Corrosion products were examined from typical pewter artifacts originating from six different submerged archaeological sites, dating to between ca. A.D. 1550 and 1733, along the eastern seaboard of North America and in the Caribbean Sea. The artifacts were viewed as 270-450-year long experiments revealing the phases and mechanisms of tin corrosion in seawater. All of the samples analyzed exhibit abhurite (Sn 3 O(OH) 2 Cl 2 ), romarchite (SnO), and hydroromarchite (Sn 3 O 2 (OH) 2 ) forming at the expense of the underlying artifact. Textural analysis suggests that abhurite is the first alteration product to form at the expense of the pewter; romarchite subsequently develops and then hydroromarchite. The outermost corrosion layers on several of the most corroded artifacts also exhibit cassiterite (SnO 2 ) as a significant and apparently final phase to form during alteration. The absence of this mineral on many samples demonstrates that, while samples appeared to be stable under the conditions that were present, cassiterite had not yet had time to form. The very limited stability field for romarchite, based on data presented by Séby et al. (Geochimica et Cosmochimica Acta, 65, 3041-3053, 2001), suggests that its presence on these artifacts may be the result of a kinetic effect. The universal appearance of this mineral on corroding tin suggests that it is a required step in the oxidation of pure tin to the final most stable phase of cassiterite. The stability of romarchite and its effectiveness as an agent of passivation can provide insight into not only the formation of tin oxides but the rate of tin corrosion. This can have significant implications in the field of artifact preservation as well as more widespread industrial applications.
We conducted an operational research study involving backyard and semicommercial farms on Java Island, Indonesia, between April 2008 and September 2009 to evaluate the effectiveness of two preventive mass vaccination strategies against highly pathogenic avian influenza (HPAI). One regimen used Legok 2003 H5N1 vaccine, while the other used both Legok 2003 H5N1 and HB1 Newcastle disease (ND) vaccine. A total of 16 districts were involved in the study. The sample size was estimated using a formal power calculation technique that assumed a detectable effect of treatment as a 50% reduction in the baseline number of HPAI-compatible outbreaks. Within each district, candidate treatment blocks with village poultry populations ranging from 80 000 to 120 000 were created along subdistrict boundary lines. Subsequently, four of these blocks were randomly selected and assigned one treatment from a list that comprised control, vaccination against HPAI, vaccination against HPAI + ND. Four rounds of vaccination were administered at quarterly intervals beginning in July 2008. A vaccination campaign involved vaccinating 100 000 birds in a treatment block, followed by another 100 000 vaccinations 3 weeks later as a booster dose. Data on disease incidence and vaccination coverage were also collected at quarterly intervals using participatory epidemiological techniques. Compared with the unvaccinated (control) group, the incidence of HPAI-compatible events declined by 32% (P = 0.24) in the HPAI-vaccinated group and by 73% (P = 0.00) in the HPAI- and ND-vaccinated group. The effect of treatment did not vary with time or district. Similarly, an analysis of secondary data from the participatory disease and response (PDSR) database revealed that the incidence of HPAI declined by 12% in the HPAI-vaccinated group and by 24% in the HPAI + ND-vaccinated group. The results suggest that the HPAI + ND vaccination significantly reduced the incidence of HPAI-compatible events in mixed populations of semicommercial and backyard poultry.
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