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Oil and gas (O&G) activity has been pervasive in the Mississippi River Delta (MRD). Here we review the life cycle of O&G fields in the MRD focusing on the production history and resulting environmental impacts and show how cumulative impacts affect coastal ecosystems. Individual fields can last 40–60 years and most wells are in the final stages of production. Production increased rapidly reaching a peak around 1970 and then declined. Produced water lagged O&G and was generally higher during declining O&G production, making up about 70% of total liquids. Much of the wetland loss in the delta is associated with O&G activities. These have contributed in three major ways to wetland loss including alteration of surface hydrology, induced subsidence due to fluids removal and fault activation, and toxic stress due to spilled oil and produced water. Changes in surface hydrology are related to canal dredging and spoil placement. As canal density increases, the density of natural channels decreases. Interconnected canal networks often lead to saltwater intrusion. Spoil banks block natural overland flow affecting exchange of water, sediments, chemicals, and organisms. Lower wetland productivity and reduced sediment input leads to enhanced surficial subsidence. Spoil banks are not permanent but subside and compact over time and many spoil banks no longer have subaerial expression. Fluid withdrawal from O&G formations leads to induced subsidence and fault activation. Formation pore pressure decreases, which lowers the lateral confining stress acting in the formation due to poroelastic coupling between pore pressure and stress. This promotes normal faulting in an extensional geological environment like the MRD, which causes surface subsidence in the vicinity of the faults. Induced reservoir compaction results in a reduction of reservoir thickness. Induced subsidence occurs in two phases especially when production rate is high. The first phase is compaction of the reservoir itself while the second phase is caused by a slow drainage of pore pressure in bounding shales that induces time-delayed subsidence associated with shale compaction. This second phase can continue for decades, even after most O&G has been produced, resulting in subsidence over much of an oil field that can be greater than surface subsidence due to altered hydrology. Produced water is water brought to the surface during O&G extraction and an estimated 2 million barrels per day were discharged into Louisiana coastal wetlands and waters from nearly 700 sites. This water is a mixture of either liquid or gaseous hydrocarbons, high salinity (up to 300 ppt) water, dissolved and suspended solids such as sand or silt, and injected fluids and additives associated with exploration and production activities and it is toxic to many estuarine organisms including vegetation and fauna. Spilled oil has lethal and sub-lethal effects on a wide range of estuarine organisms. The cumulative effect of alterations in surface hydrology, induced subsidence, and toxins interact such that overall impacts are enhanced. Restoration of coastal wetlands degraded by O&G activities should be informed by these impacts.

To compare the findings of a clinical examination with those from bitewing (BW), panoramic (Pan) and panoramic plus bitewing (PanBW) radiographs for dental caries in children.A population of 39 children, aged 3.8 to 11.9 years, who required radiographs as part of their initial assessment for care in the Department of Paediatric Dentistry (Leeds), was selected. Each subject was examined clinically for dental caries. Subsequently, a paediatric dentist and a specialist in dental radiography read the radiographs.A database in Microsoft Access was used to compare the examiners readings for each radiographic view; agreements were taken to be a consensus. Disagreements were re-viewed by both examiners to arrive at a consensus. Radiographic results were compared with those of the clinical examination.The clinical examination identified 6.0% (95% CI 4.1 to 7.8, p0.001) more carious surfaces than Pan. Clinical examinations also identified more carious surfaces than BW 1.2% (95% CI -0.7 to 3.2, p0.247) and PanBW 0.6% (95% CI -1.1 to 2.3, p0.533) but these differences were not statistically significant. When occlusal surfaces only were compared, the clinical examination identified significantly more carious occlusal surfaces then BW (15.2%, p0.001), Pan (17.1%, p0.001) and PanBW (13.5%, p0.001). Comparing the approximal surfaces only, the BW and PanBW identified significantly more carious surfaces than the clinical examination, 5.1% (p0.001) and 4.3% (p0.001) respectively.The use of a clinical examination with PanBW provided the maximum information on dental caries in the primary and mixed dentitions, particularly for approximal surfaces. This is important in planning comprehensive dental care for children.

This study was performed to evaluate the temperature, pH change, and electrolysis products at the anode during transcatheter electrocoagulation (TCEC). Stainless steel and platinum anodes insulated by standard angiographic catheters were placed in renal dialysis tubing. The tubing, filled with either saline solution or plasma, was placed in a water bath (25 degrees C) containing a cathode. Temperature was recorded at the tip of the anode, placed in saline solution, using 15 ma for 20 minutes (n = 5 for each wire and current). pH was measured during applications of 15, 30, and 60 ma for 20 minutes (n = 6 for each current, anode, and solution). The solutions were analyzed for products of electrolysis. The temperature remained constant. The pH declined to 1.5 +/- .3 (mean +/- SEM) with the platinum electrode and to 2.5 +/- .5 with the stainless steel anode. Metallic elements and oxygen were the electrolysis products recovered from the stainless steel experiments. Chlorine gas was the major product recovered from the platinum studies. These results confirm that during TCEC there is no thermal injury. The pH change at the anode is probably a major mechanism in TCEC. Different types of reactions take place at platinum and stainless steel anodes, which may account for differences between TCEC with these two electrodes.

Eight new cis-methylplatinum(II) derivatives of the type DIARSPt(CH3)X (DIARS abbreviates o-phenylenebis(dimethylarsine), where X is an anionic substituent, and [DIARSPt(CH3)L]+PF6−, where L is a neutral ligand, have been prepared. Data derived from the 13C n.m.r. spectra of these complexes are discussed and compared with data derived from the 1H n.m.r. spectra of the complexes. Comparisons with the 13C n.m.r. parameters obtained from related series of trans-methylplatinum(II) derivatives reveal marked differences between the n.m.r. cis- and trans-influences. It appears that the n.m.r. cis-influence may in part be related to a ligand's "steric bulk".

The reactions of trans-[PtH(PEt3)2(acetone)]+ and trans-[PtH(PEt3)2(CO)]+ with a variety of acetylenes are described. The geometries of the products with respect to the platinum centre and to the stereochemistry of the alkenyl group have been determined on the basis of their 1H nmr parameters. For reactions with the cation containing acetone, and particularly from a variable temperature 1H nmr study of its reaction with 2-butyne in the presence of water, the insertion pathway is shown to be entirely analogous to that for olefin insertion, involving an initial displacement of the trans ligand by acetylene, isomerization to a cis-like intermediate, migratory insertion rearrangement, and re-combination with an appropriate ligand to give either cis or trans platinum products. The insertion pathway with the carbonyl cation is dependent on the nature of the acetylene; for non-activated or weakly activated acetylenes insertion occurs via five-coordinate intermediates, but with strongly activated acetylenes, the same mechanism as with the acetone cation appears to occur, involving reversible loss of carbon monoxide.

The reactions of platinum(II) hydrides, trans-PtHXL2, where X = NO3, Cl or CH3OH, and L = PEt3 or tricyclohexylphosphine, with disubstituted acetylenes, R1C≡CR2 have been examined under a variety of conditions. From spectroscopic parameters, the gross geometry at platinum as well as the geometry of the resulting alkenyl groups in the products have been determined. The observation that all alkenyl groups have a cis geometry is consistent with a migratory insertion step involving a four-centred transition state, in which the disposition of the acetylene relative to the Pt—H bond appears to be dependent on the Pt—H bond polarity. Evidence is presented to demonstrate that this polarity depends on several factors including solvent, and ligands on Pt(II). For L = tricyclohexylphosphine, the occurrence of a side reaction which competes with insertion and which leads to a Pt(0) acetylene complex is also demonstrated, and other interesting reactions are described.

Crystal violet (hexamethyl-para-rosaniline chloride) interacts with aqueous KI-I2 during the Gram stain via a simple metathetical anion exchange to produce a chemical precipitate. There is an apparent 1:1 stoichiometry between anion (I-) and cation (hexamethyl-para-rosaniline+) during the reaction and, since the small chloride anion is replaced by the bulkier iodide, the complex formed becomes insoluble in water. It is this same precipitate which forms in the cellular substance of bacteria (both gram-positive and gram-negative types) and which initiates the Gram reaction. Potassium trichloro(eta 2-ethylene)-platinum(II), as an electronopaque marker for electron microscopy, was chemically synthesized, and it produced an anion in aqueous solution which was compatible with crystal violet for the Gram stain. It interacted with crystal violet in a similar manner as iodide to produce an insoluble complex which was chemically and physically analogous to the dye-iodide precipitate. This platinum anion therefore allows the Gram staining mechanism to be followed by electron microscopy.

Some detailed chemical studies are described of dimethylbis(perfluoropropyl)silane (I), prepared from n-perfluoropropyllithium and dimethyldichlorosilane. The hydrolytic stability of (I) towards base is described, and pyrolyses in the temperature range 185–295°, leading to the formation of dimethyldifluorosilane, (CH3)2SiF2, and fluorocarbons, are discussed. Chlorination of (I) leads to stepwise chlorination of the CH3 groups, and even excess chlorine does not cause cleavage. Bromine does not react with (I). The reaction of (I) with iodine and catalytic amounts of aluminum in boiling toluene causes rapid cleavage of C3F7 as C3F7I. The mechanisms of some of these reactions are discussed.

The reactions of methyltin hydrides with methylperfluorovinyltin compounds have been examined under heat or ultraviolet irradiation. In no case is there evidence of addition to the C=C bond. Instead, extensive reduction of the vinyl group occurs to give cis-1,2-difluorovinyltin derivatives as the principal products, with smaller amounts of the trans-1,2-difluorovinyltin isomers, 2,2′-difluorovinyltin compounds, and products containing one or more —C2H2F groups. Trimethyl- or dimethyl-tin fluoride is formed quantitatively from the corresponding hydride. In the reaction of dimethyl bis(perfluorovinyl)tin with dimethyltin dihydride, vinyl-hydrogen exchange occurs at 60° in the dark to give dimethylperfluorovinyltin hydride, while under ultraviolet irradiation partially fluorinated vinyltin compounds are formed. On the other hand, no reaction takes place between dimethyl bis(perfluorovinyl)tin and 2 moles of trimethyltin hydride in the dark at 50°, but under ultraviolet irradiation at 25°, partial vinyl-hydrogen exchange occurs, accompanied by reduction, to yield both trimethyl and dimethyl partially fluorinated vinyltin compounds. The infrared and proton magnetic resonance spectra of the products are discussed.

IrCl3(PEt3)3 is readily converted to IrHCl2(CO)(PEt3)2 by treatment with carbon monoxide in hot acetone, ethanol, or 2-methoxyethanol. Perchlorate, tetrafluoroborate, and tetraphenylborate salts containing the [IrCl2(CO)(PEt3)3]+ cation have been prepared, but attempts to obtain salts containing the [IrHCl(CO)(PEt3)3]+ cation give only the neutral hydride, IrHCl2(CO)(PEt3)2. The reactions of [IrCl2(CO)(PEt3)3]+ with ethanol, water, lithium aluminum hydride, aqueous potassium chloride solution, and sodium alkoxides are described.

Summary Changed conditions in the area under observation, and the desire to check further the conclusions reached in the last annual report of this work (5), induced us to continue observations under the same plan as last year. Monthly blood-parasite surveys in three groups treated with atabrine-plasmochin, quinine-plasmochin, both under adequate supervision, and with quinine sulphate under no supervision, gave average monthly rates for the year of 9.1, 12.3, and 18.5 per cent, respectively. The higher rate in the quinine control group was probably due to lack of supervision, and a higher percentage of children in this group (see table 2). As in the past years, the rates showed no correlation with monthly rainfall. The 12 months covered by this report were a period of low incidence, following the epidemic period of 1935, thus corroborating the views set forth in our fifth report concerning the cyclic nature of malaria incidence in Panama. The fact that our observations were made during a down-swing of the incidence curve must be considered in interpreting our results during the past year. The parasite rate, cumulative for the 12 months, but limited to those examined at every monthly survey, shows that slightly more than half of this group had parasites in the blood during the year (table 5). The same table shows that a rather high annual parasite rate can exist in all age-groups of a relatively tolerant people. The same phenomena in connection with relapse occurred during the past year as were noted in our previous reports, and we believe that relapse, especially during a year of low incidence, is responsible for a great part of the malaria rate observed. The influence of adequate treatment in lowering the blood parasite rate during an interepidemic period is well shown in table 7. Individual monthly records of all persons examined in 12 consective surveys, who were found positive two or more times, are given in tables 8, 9 and 10. Table 11 shows the incidence of species of malaria parasite found in the 811 positives discovered during the year. Estivoautumnal (subtertian) infections predominate, as in the past, and tertian infections are slightly more common in the control group. Few crescent-carriers were discovered in the surveys during the year. Heavy infections were somewhat more numerous in the two treated groups than in the control. Sixty-six infants were examined at some time during their first year of life, some only once, some for a number of months. The combined rate was 9.1 per cent, which is comparatively low, and indicates a season of low transmission. During the previous year, in which an epidemic occurred, 28 infants examined an average of 5 times, gave an annual rate of 25.0 per cent. We believe that infected adults, even though relatively tolerant to malaria infection, will not be able to support the strain of daily hard labor without the aid of medical attention. We believe this can be most economically given by supplying non-medical personnel in the field, to given immediate antimalarial treatment to those who become clinically ill; such non-medical personnel should be supervised by a qualified physician interested in tropical and industrial medicine, who should make weekly visits of inspection. Our previous experience has shown the impossibility of eradicating malaria by reducing the “seed-bed” of infection in young children and adolescents by the use of drugs. However, we do not doubt that control of malaria to a point where it will interfere little with the supply of native labor is economically possible under our local conditions by the method outlined above. Expenditures for such measures of control are economically justifiable, as they doubtless will result in increased labor efficiency, commensurable with the financial outlay involved.

The formation of addition products (CH3)3MCFHCF2Sn(CH3)3 and (CH3)3MCF[Sn(CH3)3]CF2H where M = Ge or Sn has been observed in reactions involving the ultraviolet irradiation of (CH3)3MCF=CF2 with trimethyltin hydride. The former type of addition product is more stable than the latter, and the stability of both types decreases in the order M = Si, Ge, or Sn. Evidence is presented that decomposition occurs in all cases by a β-fiuorine elimination with the formation of fluorovinyl derivatives of M and trimethyltin fluoride. Similar reactions occur between (CH3)3GeCF=CF2 and dimethyltin dihydride and between (CH3)2Ge(CF=CF2)2 and dimethyltin dihydride or trimethyltin hydride. The evidence indicates that a free radical process is involved. Spectroscopic data are presented for new organogermanium compounds.

The infrared and nuclear magnetic resonance spectra of a number of allyl-, but-3-enyl-, crotyl-, and vinyl-tin compounds in dimethylsulfoxide have been examined and compared with measurements made on solutions in methylene chloride and carbon tetrachloride. It is concluded from the changes which occur in the positions of the ν(C=C) bands and in the chemical shifts of the olefinic protons that there are no significant π-interactions between the d orbitals on tin and the olefinic π-systems.

Summary and Conclusions The present paper reports four year's work with drug control of malaria, in an unsanitated area in Panama. Various combinations of anti-malarial drugs were used including quinine sulphate alone or with plasmochin, and atabrine alone or with plasmochin. None of the methods used were particularly successful in reducing the malaria rate, except possibly the combination of atabrine and plasmochin. Monthly surveys over four years indicate the presence of cyclical variations in malaria parasite rate extending over several years. If treatment of any sort happens to be given during a down-swing in rate, success is nearly sure to follow; but if it is given on an upswing in rate, apparently nothing can stop the natural course of the cycle. Even atabrine, the most useful drug we have to date, was unable in 1933 to reduce materially the parasite rate during a period of eight months. The effect of the addition of plasmochin to atabrine and to quinine in 1934 is obscured by the greater effect of the naturally decreasing malaria rate, as evidenced by comparative rates in our control town. It will be necessary to continue the administration of both drugs during the next up-swing of the parasite rate, in order to ascertain its effect. Although we feel that the recent improvement in malaria parasite rate is not due solely to our efforts, we have no doubt but that the general health of our villagers is much improved over its condition in 1929, before our work started. At that time there was much more evidence, in the form of anemia, cachexia and other indications of malarial infection, of the ravages of the disease. By continued work we have reduced the numbers of chronic infections, and have taught the people to apply for drug treatment for their fevers, and have effected a consequent material improvement in general health conditions which may enable them to resist successfully the next onslaught of the disease. Part II of the paper summarizes the malaria parasite rates found in twelve monthly surveys in 5 towns in the valley of the chagres River, and compares the percentages with those found in previous years. The evidence of our control town indicates that 1934 was a year of naturally declining parasite rates. The possibility that immunity is a family trait is discussed, and several illustrations are given in support of the theory.

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