Weathering geochronology by (U-Th)/He dating of goethite

Nine samples of supergene goethite (FeOOH) from Brazil and Australia were selected to rest the suitability of this mineral for (U-Th)/He dating. Measured He ages ranged from 61 to 8 Ma and were reproducible to better than a few percent despite very large Variations in [U] and [Th]. In all Samples with internal stratigraphy or independent age constraints, the He ages corroborated the expected relationship's. These data demonstrate that internally consistent He ages can be obtained on goethite. but do not prove quantitative 4 He retention. To assess possible diffusive He loss, stepped-heating experiments were performed on two goethite samples that were subjected to proton irradiation to produce a homogeneous distribution of spallogenic He-3. The He-3 release pattern indicates the presence of at least two diffusion domains, one with high helium retentivity and the other with very low retentivity at Earth surface conditions. The low retentivity domain, which accounts for similar to 5% of He-3, contains no natural He-4 and may represent poorly crystalline or intergranular material which has lost all radiogenic He-4 by diffusion in nature. Diffusive loss of He-3 from the high retentivity domain is independent of the macroscopic dimensions of the analyzed polycrystalline aggregate, so probably represents diffusion from individual micrometer-size goethite crystals. The He-2/He-3 evolution during the incremental heating experiments shows that the high retentivity domain has retained 90%-95% of its radiogenic helium. This degree of retentivity is in excellent agreement with that independently predicted from the helium diffusion coefficients extrapolated to Earth surface temperature and held for the appropriate duration. Considering both the high and low retentivity domains, these data indicate that one of the samples retained 90% of its radiogenic He-4 over 47.5 Ma and the other retained 86% over 12.3 Ma. Thus while diffusive-loss corrections to supergene goethite He ages are required. these initial results indicate that the corrections are not extremely large and can be rigorously quantified using the proton-irradiation He-4/He-3 method. Copyright (C) 2005 Elsevier Ltd.

Dating paleochannel iron ore by (U-Th)/He analysis of supergene goethite, Hamersley province, Australia

(U-Th)/He dating of late-stage authigenic goethite, combined with corrections for diffusive loss of He-4 by the He-4/He-3 methodology, reveals strong correlation between a sample's age and its depth in ferruginized channel sediments from the Yandicoogina deposit, Western Australia. Corrected ages, ranging from ca. 18 Ma near the surface to ca. 5 Ma at the bottom of the profile, indicate that ferruginization of the aggraded channels becomes progressively younger with depth. This trend is consistent with goethite precipitation at the groundwater-atmosphere interface during water table drawdown driven by the aridification of Western Australia during the Neogene. The results demonstrate that the (U-Th)/He system is ideal for dating goethite if diffusive loss corrections are applied. The approach is suitable for dating weathering reactions on Earth and should also be suitable for dating Fe oxyhydroxides in the Martian regolith.

The gap equations for spin singlet and triplet ferromagnetic superconductors

We derive gap equations for superconductivity in coexistence with ferromagnetism. We treat singlet and triplet states With either equal spin pairing (ESP) or opposite spin pairing (OSP) states, and study the behaviour of these states as a function of exchange splitting. For the s-wave singlet state we find that our gap equations correctly reproduce the Clogston-Chandrasekhar limiting behaviour and the phase diagram of the Baltensperger-Sarma equation (excluding the FFLO region). The singlet superconducting order parameter is shown to be independent of exchange splitting at zero temperature, as is assumed in the derivation of the Clogston-Chandrasekhar limit. P-wave triplet states of the OSP type behave similarly to the singlet state as a function of exchange splitting. On the other hand, ESP triplet states show a very different behaviour. In particular, there is no Clogston-Chandrasekhar limiting and the superconducting critical temperature, T-C, is actually increased by exchange splitting.

The costs of caring for patients in a tertiary referral Australian intensive care unit

We determined the direct cost of an Intensive Care Unit (ICU) bed in a tertiary referral Australian ICU and the cost drivers thereof, by retrospectively analysing a number of prospectively designed Hospital- and Unit-specific electronic databases. The study period was a financial year, from 1 July 2002 to 30 June 2003. There were 1615 patients occupying 5692 fractional occupied bed days at a total cost of A$15,915,964, with an average length of stay of 3.69 days (range 0.5-77, median 1.06, interquartile range 2.33). The main cost driver not incorporated into this analysis was blood products (paid for centrally). The average costs of an ICU day and total stay per patient were A$2670 and A$9852 respectively. Staff-related charges were 68.76%, with consumables related expenditure making up 19.65%, clinical support services 9.55% and capital equipment 2.04%. Overtime charges and nursing agency staff were 19.4% of staff-related charges (2.9% for agency staff), 3.9% lower than expenditure associated with full-time employment charges, such as pension and leave. The emergency nature of ICU means it is difficult to accurately set a nursing establishment to cater for all admissions and therefore it is hard to decide what is an acceptable percentage difference between agency/overtime costs compared with the costs associated with full-time staff appointments. Consumable expenditure is likely to increase the most with new innovation and therapies. Using protocol driven practices may tighten and control costs incurred in ICU.

Recombinant human activated protein C improves pulmonary function in ovine acute lung injury resulting from smoke inhalation and sepsis

Objective: To investigate the effects of recombinant human activated protein C (rhAPC) on pulmonary function in acute lung injury (ALI) resulting from smoke inhalation in association with a bacterial challenge. Design: Prospective, randomized, controlled, experimental animal study with repeated measurements. Setting: Investigational intensive care unit at a university hospital. Subjects: Eighteen sheep (37.2 +/- 1.0 kg) were operatively prepared and randomly allocated to either the sham, control, or rhAPC group (n = 6 each). After a tracheotomy had been performed, ALI was produced in the control and rhAPC group by insufflation of 4 sets of 12 breaths of cotton smoke. Then, a 30 mL suspension of live Pseudomonas aeruginosa bacteria (containing 2-5 x 10(11) colony forming units) was instilled into the lungs according to an established protocol. The sham group received only the vehicle, i.e., 4 sets of 12 breaths of room air and instillation of 30 mL normal saline. The sheep were studied in the awake state for 24 hrs and were ventilated with 100% oxygen. RhAPC (24 mu g/kg/hr) was intravenously administered. The infusion was initiated 1 hr post-injury and lasted until the end of the experiment. The animals were resuscitated with Ringer's lactate solution to maintain constant pulmonary artery occlusion pressure. Measurements and Main Results., In comparison with nontreatment in controls, the infusion of rhAPC significantly attenuated the fall in PaO2/FiO(2) ratio (control group values were 521 +/- 22 at baseline [BL], 72 +/- 5 at 12 hrs, and 74 +/- 7 at 24 hrs, vs. rhAPC group values of 541 +/- 12 at BL, 151 +/- 29 at 12 hours [p < .05 vs. control], and 118 +/- 20 at 24 hrs), and significantly reduced the increase in pulmonary microvascular shunt fraction (Qs/Qt; control group at BL, 0.14 +/- 0.02, and at 24 hrs, 0.65 +/- 0.08; rhAPC group at BL, 0.24 +/- 0.04, and at 24 hrs, 0.45 +/- 0.02 [p < .05 vs. control]) and the increase in peak airway pressure (mbar; control group at BL, 20 +/- 1, and at 24 hrs, 36 +/- 4; rhAPC group at BL, 21 +/- 1, and at 24 hrs, 28 +/- 2 [p < .05 vs. control]). In addition, rhAPC limited the increase in lung 3-nitrotyrosine (after 24 hrs [%]: sham, 7 +/- 2; control, 17 +/- 1; rhAPC, 12 +/- 1 [p < .05 vs. control]), a reliable indicator of tissue injury. However, rhAPC failed to prevent lung edema formation. RhAPC-treated sheep showed no difference in activated clotting time or platelet count but exhibited less fibrin degradation products (1/6 animals) than did controls (4/6 animals). Conclusions. Recombinant human activated protein C attenuated ALI after smoke inhalation and bacterial challenge in sheep, without bleeding complications.

Pharmacological evaluation of an [I-123] labelled imidazopyridine-3-acetamide for the study of benzodiazepine receptors

In vitro binding of the iodinated imidazopyri dine, N',N'-dimethyl-6-methyl-(4'-[I-123]iodophenyl)imidazo[1,2-a]pyridine-3-acetamide [I-123]IZOL to benzodiazepine binding sites on brain cortex, adrenal and kidney membranes is reported. Saturation experiments showed that [I-123]IZOL, bound to a single class of binding site (n(H)=0.99) on adrenal and kidney mitochondrial membranes with a moderate affinity (K-d=30 nM). The density of binding sites was 22 +/- 6 and 1.2 +/- 0.4 pmol/mg protein on adrenal and kidney membranes, respectively. No specific binding was observed in mitochondrial-synaptosomal membranes of brain cortex. In biodistribution studies in rats, the highest uptake of [I-123]IZOL was found 30 min post injection in adrenals (7.5% ID/g), followed by heart, kidney, lung (1% ID/g) and brain (0.12% ID/g), consistent with the distribution of peripheral benzodiazepine binding sites. Pre-administration of unlabelled IZOL and the specific PBBS drugs, PK 11195 and Ro 5-4864 significantly reduced the uptake of [I-123]IZOL by 30% (p < 0.05) in olfactory bulbs and by 51-86% (p < 0.01) in kidney, lungs, heart and adrenals, while it increased by 30% to 50% (p < 0.01) in the rest of the brain and the blood. Diazepam, a mixed CBR-PBBS drug, inhibited the uptake in kidney, lungs, heart, adrenals and olfactory bulbs by 32% to 44% (p < 0.01) but with no effect on brain uptake and in blood concentration. Flumazenil, a central benzodiazepine drug and haloperidol (dopamine antagonist/sigma receptor drug) displayed no effect in [I-123]IZOL in peripheral organs and in the brain. [I-123]IZOL may deserve further development for imaging selectively peripheral benzodiazepine binding sites. (c) 2006 Elsevier Inc. All rights reserved.