Recovery from disturbance requires resynchronization of ecosystem nutrient cycles.

Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance.

Outcome from treatment of Pneumocystis jirovecii pneumonia with co-trimoxazole.

A retrospective case-notes audit of 359 HIV-1-infected adult patients with first-episode laboratory-confirmed Pneumocystis jirovecii pneumonia treated with co-trimoxazole (from 1987 adjuvant steroids were used if PaO(2) <9.3 kPa) showed that only 230/359 (64%) patients completed treatment; 104 (29%) patients had treatment-limiting toxicity; rash occurred in 4/60 (6.7%) patients in 1985-1988 and in 15/47 (31.9%) in 2005-2008. Twenty-five patients (7%) failed co-trimoxazole treatment. Overall mortality was 13.6% (49/359); mortality among patients who failed co-trimoxazole treatment was 48% (12/25) and by contrast mortality was 4.8% (5/104) among patients with treatment-limiting toxicity.

Iron-magnesium silicate bioweathering on Earth (and Mars?).

We examined the common, iron-magnesium silicate minerals olivine and pyroxene in basalt and in mantle rocks to determine if they exhibit textures similar to bioweathering textures found in glass. Our results show that weathering in olivine may occur as long, narrow tunnels (1-3 microm in diameter and up to 100 microm long) and as larger irregular galleries, both of which have distinctive characteristics consistent with biological activity. These weathering textures are associated with clay mineral by-products and nucleic acids. We also examined olivine and pyroxene in martian meteorites, some of which experienced preterrestrial aqueous alteration. Some olivines and pyroxenes in the martian meteorite Nakhla were found to contain tunnels that are similar in size and shape to tunnels in terrestrial iron-magnesium silicates that contain nucleic acids. Though the tunnels found in Nakhla are similar to the biosignatures found in terrestrial minerals, their presence cannot be used to prove that the martian alteration features had a biogenic origin. The abundance and wide distribution of olivine and pyroxene on Earth and in the Solar System make bioweathering features in these minerals potentially important new biosignatures that may play a significant role in evaluating whether life ever existed on Mars.

High frequency ventilation trial. Nine year follow up of lung function.

The high frequency ventilation (HIFI) trial for hyaline membrane disease (HMD) showed no advantage of high frequency over conventional ventilation in pulmonary outcomes after 24 months. The present study tested the hypothesis that there would be no significant difference in childhood lung function between patients who had been ventilated by either method. Thirty-two children aged 8-9 years who completed the HIFI trial were asked to return for pulmonary function tests. For purposes of analysis, the patient population was divided according to mode of ventilation, and by diagnosis of bronchopulmonary dysplasia (BPD) or HMD. Results were compared to those of 15 term-born, matched, controls. Lung function tests showed a mildly obstructive pattern in prematurely born children. More severe obstruction was seen in those children who had physician-diagnosed asthma or who had used bronchodilators in the past. The prevalence of mild obstructive pattern on pulmonary function testing in preterm infants with HMD or BPD was similar in those who received high frequency vs. conventional ventilation. Factors other than the mode of ventilation exert greater influence on pulmonary outcome in survivors of lung disease of prematurity.

A comparison of personal response services in Canada and the UK.

Personal response services operating over public telephone networks are now widespread in Western Europe and North America. They serve the needs of a million people in the UK and a further two to three million elsewhere. While most clients are elderly, the scope of such services is extending to people with support needs of all ages, especially where there are medical risks or a likelihood of falls. Such services are, therefore, on a convergent course with those concerned with telemedicine. A study of two personal response services was carried out, one based in Ottawa (Canada) and the other in Oldham (UK). The parallels and contrasts were examined through a survey involving personal interviews with samples of clients. Thirty-eight valid personal interviews were completed, 20 in Ottawa and 18 in Oldham, representing 14% and 53% respectively of all service clients in the survey areas. It is concluded that services established within the health sector (such as many in Canada) are better placed to accommodate change. Convergence with telemedicine will, as a result, be facilitated. In the UK, health authorities and trusts are likely to develop their own telemedicine services in competition with current providers of personal response services, thus delaying convergence.

Telecare equipment in the home. Issues of intrusiveness and control.

Telecare in the home offers substantial benefits to users. However, the manner of its development and technological configuration will determine the extent to which it is acceptable and will meet clinical and social objectives. There are important issues of intrusiveness and control. An ethical framework for telecare is needed.

Telecare at home: factors influencing technology choices and user acceptance.

Acceptance of telecare technologies in the home is strongly influenced by factors that relate to dwelling design and the ways in which independent living is promoted. The experience to date of personal response systems (and services) provides some indication of the reasons why users may either resist their introduction or not use such technologies after they have been introduced. Telecare systems and services are poised to incorporate medical and other sensors, so that the manner of their provision, installation and control becomes an important consideration for service providers. A clear ethical framework is called for.

The petrochemistry of Jake_M: a martian mugearite.

"Jake_M," the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, differs substantially in chemical composition from other known martian igneous rocks: It is alkaline (>15% normative nepheline) and relatively fractionated. Jake_M is compositionally similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. By analogy with these comparable terrestrial rocks, Jake_M could have been produced by extensive fractional crystallization of a primary alkaline or transitional magma at elevated pressure, with or without elevated water contents. The discovery of Jake_M suggests that alkaline magmas may be more abundant on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).

Soil diversity and hydration as observed by ChemCam at Gale crater, Mars.

The ChemCam instrument, which provides insight into martian soil chemistry at the submillimeter scale, identified two principal soil types along the Curiosity rover traverse: a fine-grained mafic type and a locally derived, coarse-grained felsic type. The mafic soil component is representative of widespread martian soils and is similar in composition to the martian dust. It possesses a ubiquitous hydrogen signature in ChemCam spectra, corresponding to the hydration of the amorphous phases found in the soil by the CheMin instrument. This hydration likely accounts for an important fraction of the global hydration of the surface seen by previous orbital measurements. ChemCam analyses did not reveal any significant exchange of water vapor between the regolith and the atmosphere. These observations provide constraints on the nature of the amorphous phases and their hydration.

Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow.

The Rocknest aeolian deposit is similar to aeolian features analyzed by the Mars Exploration Rovers (MERs) Spirit and Opportunity. The fraction of sand <150 micrometers in size contains ~55% crystalline material consistent with a basaltic heritage and ~45% x-ray amorphous material. The amorphous component of Rocknest is iron-rich and silicon-poor and is the host of the volatiles (water, oxygen, sulfur dioxide, carbon dioxide, and chlorine) detected by the Sample Analysis at Mars instrument and of the fine-grained nanophase oxide component first described from basaltic soils analyzed by MERs. The similarity between soils and aeolian materials analyzed at Gusev Crater, Meridiani Planum, and Gale Crater implies locally sourced, globally similar basaltic materials or globally and regionally sourced basaltic components deposited locally at all three locations.

Cardiopulmonary exercise performance in prematurely born children.

Prematurely born children have reduced peak VO2 compared with their peers, inferentially attributed to ventilatory limitation. The primary purpose of this study was to compare exercise ventilation and cardiac output in a sample of childhood survivors of lung disease of prematurity with those of a control group to elucidate reasons for lower peak VO2. A secondary aim was to describe and compare the ventilatory response to incremental exercise. Thirty-two children, aged 8-9 y, were recalled for lung function and progressive exercise tests. Fifteen of them also performed submaximal exercise with measurement of cardiac output (indirect [CO2] Fick) and physiologic dead space. Results were compared with those of term-born, age- and sex-matched, control children. Pulmonary function tests showed mild airflow limitation. Peak VO2 was lower in prematurely born children compared with control children, and was correlated with lean body mass. Their heart rate-VO2 relationship and stroke volume were similar to that of term-born control children. Children with a history of bronchopulmonary dysplasia and hyaline membrane disease as infants exhibited greater exercise hyperpnea than did healthy control children, because of higher breathing frequency, and maintained lower end-tidal PCO2 during submaximal exercise. Physiologic dead space normalized for body weight was similar in preterm and term-born children. Lower peak VO2 in this population is not caused by cardiopulmonary factors, but is best predicted by lean body mass. Ventilation did not limit exercise performance, although it appears that breathing during exercise is regulated differently in prematurely born children than in term-born children.

Silicone oil insertion. A review of 127 consecutive cases.

Silicone oil was used in combination with vitrectomy to treat 127 cases of complicated retinal detachments. An initial anatomic success in 120 cases (94%) was reduced to 68 (54%) after an average follow-up of 32 months and was attributable to ongoing proliferative vitreo-retinopathy (PVR). The indications for the use of silicone oil were: 1. Retinal detachment complicated by PVR (107 cases), 20 of which required multiple operations. Anatomic success was achieved in 59 (55%) and of these 23 (40%) had a visual acuity of 6/60. 2. Giant retinal tears (GRT) (7 cases). Four (57%) of these remained attached, three (75%) having a final vision of 6/36. 3. GRTs complicated by PVR (8 cases). Four (50%) were anatomically successful and two had a final vision of 6/60. 4. Proliferative diabetic retinopathy (5 cases). Two (40%) remained attached and one of these (50%) had hand movements vision. The silicone oil was removed electively in 23 eyes, 16 (70%) of these being anatomically successful. Oil was removed in 43 eyes because of complications, and in 20 (46%) of these, the retina remained attached at the end of follow-up. Complications included cataract in all 14 phakic eyes; rubeosis in 19 eyes (15%); corneal opacification in 52 eyes (41%), there being no clear cut difference between those eyes with an inferior iridectomy (35 of 85 eyes--41%) and those without (12 of 29 eyes--41%); and raised intraocular pressure in 55 eyes (43%). We conclude that although far from being ideal, silicone oil appears to have played some part in achieving the successful results reported in this study.

The quadrate suture. A new technique for temporary intraoperative mydriasis.

A simple, quick, effective, and atraumatic closed suturing technique for producing and maintaining intraoperative pupillary dilation is described. Readily available sutures, needles, and syringes are used in a way that eliminates the need for paracenteses, sclerotomies, and special equipment.

Building a children's health network: city-wide computer linkages among heterogeneous sites for pediatric primary care.

For many infants and children in our cities, quality of care and health status outcomes suffer due to poor continuity and coordination among ambulatory care sites. Despite proximity to technologically-advanced secondary and tertiary institutions, primary care services for children are fragmented, multiple-site use is common, and data flow among providers serving the same patients is primitive. Preventive and acute health care is often incomplete or redundant, and aggregate information for public health purposes is insufficient. This paper focuses on the development of a city-wide computer-based pediatric health care network to improve provider decision-making and follow-through, parent role in their children's care, and community-wide data. A process of building consensus for a regional system is presented, addressing issues of establishing a uniform data base, coordination among heterogeneous institutions, system development, confidentiality, and integration with public health reporting and planning functions.