A trade-off between plant and soil carbon storage under elevated CO2.

Terrestrial ecosystems remove about 30 per cent of the carbon dioxide (CO2) emitted by human activities each year1, yet the persistence of this carbon sink depends partly on how plant biomass and soil organic carbon (SOC) stocks respond to future increases in atmospheric CO2 (refs. 2,3). Although plant biomass often increases in elevated CO2 (eCO2) experiments4-6, SOC has been observed to increase, remain unchanged or even decline7. The mechanisms that drive this variation across experiments remain poorly understood, creating uncertainty in climate projections8,9. Here we synthesized data from 108 eCO2 experiments and found that the effect of eCO2 on SOC stocks is best explained by a negative relationship with plant biomass: when plant biomass is strongly stimulated by eCO2, SOC storage declines; conversely, when biomass is weakly stimulated, SOC storage increases. This trade-off appears to be related to plant nutrient acquisition, in which plants increase their biomass by mining the soil for nutrients, which decreases SOC storage. We found that, overall, SOC stocks increase with eCO2 in grasslands (8 ± 2 per cent) but not in forests (0 ± 2 per cent), even though plant biomass in grasslands increase less (9 ± 3 per cent) than in forests (23 ± 2 per cent). Ecosystem models do not reproduce this trade-off, which implies that projections of SOC may need to be revised.

Response of Root Respiration to Warming and Nitrogen Addition Depends on Tree Species.

Roots contribute a large fraction of CO2 efflux from soils, yet the extent to which global change factors affect root-derived fluxes is poorly understood. We investigated how red maple (Acer rubrum) and red oak (Quercus rubra) root biomass and respiration respond to long-term (15 years) soil warming, nitrogen addition, or their combination in a temperate forest. We found that ecosystem root respiration was decreased by 40% under both single-factor treatments (nitrogen addition or warming) but not under their combination (heated × nitrogen). This response was driven by the reduction of mass-specific root respiration under warming and a reduction in maple root biomass in both single-factor treatments. Mass-specific root respiration rates for both species acclimated to soil warming, resulting in a 43% reduction, but were not affected by N addition or the combined heated × N treatment. Notably, the addition of nitrogen to warmed soils alleviated thermal acclimation and returned mass-specific respiration rates to control levels. Oak roots contributed disproportionately to ecosystem root respiration despite the decrease in respiration rates as their biomass was maintained or enhanced under warming and nitrogen addition. In contrast, maple root respiration rates were consistently higher than oak, and this difference became critical in the heated × nitrogen treatment, where maple root biomass increased, contributing significantly more CO2 relative to single-factor treatments. Our findings highlight the importance of accounting for the root component of respiration when assessing soil carbon loss in response to global change and demonstrate that combining warming and N addition produces effects that cannot be predicted by studying these factors in isolation.

The role of isohydric and anisohydric species in determining ecosystem-scale response to severe drought.

Ongoing shifts in the species composition of Eastern US forests necessitate the development of frameworks to explore how species-specific water-use strategies influence ecosystem-scale carbon (C) cycling during drought. Here, we develop a diagnostic framework to classify plant drought-response strategies along a continuum of isohydric to anisohydric regulation of leaf water potential (Ψ(L)). The framework is applied to a 3-year record of weekly leaf-level gas exchange and Ψ measurements collected in the Morgan-Monroe State Forest (Indiana, USA), where continuous observations of the net ecosystem exchange of CO2 (NEE) have been ongoing since 1999. A severe drought that occurred in the middle of the study period reduced the absolute magnitude of NEE by 55%, though species-specific responses to drought conditions varied. Oak species were characterized by anisohydric regulation of Ψ(L) that promoted static gas exchange throughout the study period. In contrast, Ψ(L) of the other canopy dominant species was more isohydric, which limited gas exchange during the drought. Ecosystem-scale estimates of NEE and gross ecosystem productivity derived by upscaling the leaf-level data agreed well with tower-based observations, and highlight how the fraction of isohydric and anisohydric species in forests can mediate net ecosystem C balance.

Modeling Global Carbon Costs of Plant Nitrogen and Phosphorus Acquisition.

Most Earth system models (ESMs) do not explicitly represent the carbon (C) costs of plant nutrient acquisition, which leads to uncertainty in predictions of the current and future constraints to the land C sink. We integrate a plant productivity-optimizing nitrogen (N) and phosphorus (P) acquisition model (fixation & uptake of nutrients, FUN) into the energy exascale Earth system (E3SM) land model (ELM). Global plant N and P uptake are dynamically simulated by ELM-FUN based on the C costs of nutrient acquisition from mycorrhizae, direct root uptake, retranslocation from senescing leaves, and biological N fixation. We benchmarked ELM-FUN with three classes of products: ILAMB, a remotely sensed nutrient limitation product, and CMIP6 models; we found significant improvements in C cycle variables, although the lack of more observed nutrient data prevents a comprehensive level of benchmarking. Overall, we found N and P co-limitation for 80% of land area, with the remaining 20% being either predominantly N or P limited. Globally, the new model predicts that plants invested 4.1 Pg C yr-1 to acquire 841.8 Tg N yr-1 and 48.1 Tg P yr-1 (1994-2005), leading to significant downregulation of global net primary production (NPP). Global NPP is reduced by 20% with C costs of N and 50% with C costs of NP. Modeled and observed nutrient limitation agreement increases when N and P are considered together (r 2 from 0.73 to 0.83).

Phacoemulsification in a patient with marked cervical kyphosis.

A patient with long-standing ankylosing spondylitis and chronic uveitis needed cataract extraction in his only eye. Extensive spinal deformities, including cervical kyphosis, prevented him from being positioned satisfactorily for surgery using a routine head-end or temporal position for the surgeon. The best possible position for surgery was achieved using an orthopedic operating table, which allowed the patient's head to be reclined to a position of 60 degrees to the horizontal. Successful combined phacoemulsification and trabeculectomy was then performed, although the angle of approach for the surgeon and the operating microscope was awkward.

Visual outcome with the array multifocal intraocular lens in patients with concurrent eye disease.

PURPOSE: To evaluate whether the distance visual outcome with the Array(R) multifocal intraocular lens (IOL) is comparable to that of a monofocal IOL in eyes with concurrent disease and to assess whether these eyes benefit from the IOL's multifocality. SETTING: Department of Ophthalmology, Arrowe Park Hospital, Wirral, United Kingdom. METHODS: This prospective study comprised 133 eyes of 111 patients with cataract and concurrent disease such as macular degeneration, glaucoma, and diabetic retinopathy. Eighty-one eyes (70 patients) received an Array multifocal IOL after phacoemulsification. A control group of 52 eyes (41 patients) received a monofocal IOL of similar design (AMO SI-40NB). Visual outcomes in terms of uncorrected and best corrected distance and near acuities were evaluated. RESULTS: In both the multifocal and the monofocal IOL groups, the number of eyes achieving a best corrected visual acuity of 6/12 and N8 or better (55 and 37 eyes, respectively) was comparable (P > or =.999; 95% confidence interval [CI] -0.152 to 0.172). There was a borderline statistically significant difference in the number of eyes achieving an uncorrected visual acuity of 6/12 or better and N8 or better in the multifocal IOL (11 eyes) and monofocal (2 eyes) groups (P =.047, 95% CI -0.001 to 0.196). A significantly higher number of eyes in the multifocal group (40 eyes) than in the monofocal IOL group (4 eyes) achieved a distance-corrected acuity of 6/12 and N8 or better (P =.0001; 95% CI 0.274 to 0.539). CONCLUSIONS: The Array multifocal IOL produced distance visual outcomes comparable to those of the AMO SI-40NB monofocal IOL in patients with concurrent eye disease. A significant proportion of these patients benefited from the IOL's multifocality. Management of associated eye disease was not compromised by the nature of the IOL.

A study of printed spiral coils for neuroprosthetic transcranial telemetry applications.

We have explored the use of printed spiral coils (PSC's) for neuroprosthetic transcranial telemetry applications. We fabricated two-dimensional PSC's on a thin (25 microns) polyimide substrate using copper (35 microns) as a conducting material. All the coils had a fixed inner diameter of 1.0 cm. We fabricated two sets of coils. One set of coils consisted of 2- to 5-turn circular and square spiral coils and had different trace widths (W), different spacings (S) between adjacent traces, and different outer diameters. The other set of coils consisted of 5-turn circular spiral coils and had fixed inner and outer diameters but different W to S ratios. We measured loss resistances (Rs and Rp) and quality factors (Q) of these coils at different resonating frequencies in the range of 5-40 MHz. Over this frequency range, we observed that for fixed inner and outer diameters, the coil with the largest W achieved the lowest Rs and the highest Rp and Q. These electrical properties and the fact that these coils can conform to the complex convoluted cortical surface suggest that a PSC [15] can provide a viable alternative to a conventional wire-wound coil for neuroprosthetic transcranial telemetry applications.

Digital fundus imaging using a scanning laser ophthalmoscope.

While many systemic diseases have ophthalmic manifestations with visible pathological features affecting the fundus, diabetic eye disease is of particular interest. There are many advantages in using digital image analysis to quantify the extent of retinal pathology in diabetes particularly to monitor its progression. However, the usual method of imaging involves photographing the retina using a fundus camera. Not only does this require that the photographs be digitized prior to analysis, but the resulting illumination across the image is non-uniform and this creates problems in digital image analysis. This paper describes the construction of a scanning laser ophthalmoscope interfaced to a computer, which has a number of significant advantages for digital retinal imaging. Firstly, it has better uniformity of illumination than the fundus camera and operates at much lower light levels. Secondly, it permits imaging at various wavelengths with no consequent degradation in image quality; in particular, the value of imaging at infrared wavelengths to give greater tissue penetration is demonstrated. Finally, by introducing the capability for confocal imaging, tomographic images can be taken, improving the perceptibility of features situated deep in the retina. Typical images are shown to demonstrate the potential of this instrument.

A high capacity transcutaneous energy transmission system.

A transcutaneous energy transmission system is described that transmits up to 60 W for use by a mechanical circulatory support system or other internal device. It contains an input power conditioning circuit that permits it to sustain the required output with input voltages ranging from 10 to 16 V. The transcutaneous energy transmission system demonstrated a best overall efficiency of 77% when connected to a resistive load and 74% when connected to a mechanical circulatory support system pumping up to 8.0 L/min to a mock circulation system. These figures included the losses in the conditioning circuit, which, when operated separately, had an efficiency of 94%. By tuning the resonant frequency of the primary, an output with only a 10% variation was achieved with coils separated by between 0 and 25 mm. A model of the inductively coupled resonant circuits was analyzed and a closed form solution obtained that verified the equations reported by Galbraith et al. Additional useful results obtained included an expression for the efficiency of the power transfer through the coupled circuits and the ratio of the current circulating in the primary and secondary coils. These results indicate that information useful for control of the output voltage of the secondary may be available in the primary circuit.

Bilateral anterior ischaemic optic neuropathy due to optic disc drusen.

PURPOSE: To report a case of bilateral anterior ischaemic optic neuropathy due to buried optic disc drusen. METHODS: Case report. RESULTS: A 64-year-old man presented with swollen optic discs and features suggestive of anterior ischaemic optic neuropathy (AION) in the left and right eye on two separate occasions ten months apart. Detailed ocular examination at presentation and systemic investigations did not reveal an underlying cause for the AION. At a later follow-up, optic disc drusen were noted in both eyes as partial optic atrophy had set in. This was confirmed by ultrasound B scan and demonstration of autofluorescence. CONCLUSIONS: In patients presenting with AION uncommon underlying causes must be considered. Routine ultrasound B scan at presentation can easily establish or exclude optic disc drusen as an underlying cause.

Steroid induced glaucoma: a report of two cases with a review of morbidity and prescribing in general practice.

An eight-week general practice based prospective study was carried out to determine the incidence and prevalence of various eye conditions and the frequency of prescription of different topical eye preparations. The most frequently diagnosed eye conditions were infectious conjunctivitis (35%), glaucoma (16%), allergic conjunctivitis (11%), and keratoconjunctivitis sicca (9%). Betamethasone was the fourth most commonly prescribed preparation (9%). Eye preparations containing steroids accounted for 14% of prescriptions. Two cases of steroid induced glaucoma are presented as an illustration of the potential hazards of these preparations. The pathogenesis of steroid induced glaucoma is discussed.

Lacrimal canalicular stenosis associated with systemic 5-fluorouacil therapy.

PURPOSE: Ocular side effects of systemic 5-fluorouracil therapy include excessive lacrimation which often resolves on cessation of therapy. Permanent stenosis of lacrimal puncta and canaliculi is rare. This report highlights this uncommon complication of 5-fluorouracil therapy. METHODS: Report of two cases and review of literature. RESULTS: Severe stenosis of puncta and canaliculi may be associated with prolonged systemic 5-fluorouracil therapy. CONCLUSION: It is important for both the oncologist and ophthalmologist to be aware of the potential ocular toxicity of 5-fluorouracil. Surgical management to relieve the epiphora is often challenging, and early intervention may be beneficial.

Influence of rectal washout on bacterial counts in the rectal stump.

Forty-three patients undergoing a restorative colorectal resection were randomized to have their rectal stump washed out with either 0.9 per cent saline, 2.5 per cent povidone-iodine or 0.3 per cent sodium hypochlorite. The bacterial counts before and after washout for Escherichia coli and Bacteroides fragilis were compared using the Mann-Whitney U test. There was no significant difference in the counts for E. coli before and after washout with saline (log 9.7-log 9.7 organisms/ml) and saline had no influence on the counts of B. fragilis (log 7.9-log 6.5 organisms/ml). Hypochlorite was associated with a significant reduction in E. coli counts (log 6.1-log 1.1 organisms/ml, P less than 0.005) and the counts of B. fragilis (log 8.1-log 0.0 organisms/ml, P less than 0.005). The counts of B. fragilis were significantly reduced by povidone-iodine (log 8.1-log 1.1 organisms/ml, P less than 0.005) but there was no significant reduction in counts of E. coli (log 5.6-log 5.3 organisms/ml). The data suggest that sodium hypochlorite is better than povidone-iodine or saline as a rectal washout for colorectal anastomosis.

Effectiveness of optometrist screening for diabetic retinopathy using slit-lamp biomicroscopy.

PURPOSE: To assess the effectiveness of optometrists as screeners for diabetic retinopathy using slit-lamp binocular indirect ophthalmoscopy through dilated pupils. METHODS: Prospective study of a screening scheme. Screening was performed by 27 locally accredited optometrists in their practice. The referral protocol used a new simple grading system of retinopathy, especially designed for use in an optometrist screening programme. All positive referrals and 10% of negative referrals were reexamined by an ophthalmologist. Sensitivity, specificity, likelihood ratios and technical failure rates were calculated. RESULTS: The optometrists screened 4904 people with diabetes in 18 months. 'Subthreshold' (screen negative) reports accounted for 4438 (90.5% of 4904); 429 (9.67%) of these were re-examined at secondary screening. There was disagreement regarding grading in 13 patients, of whom 5 (1.16% of 429) had sight-threatening retinopathy (STDR); this extrapolates to 52 patients if all the 4438 test-negatives had been examined. Of the 371 'threshold' patients, 112 (30.18%) were false positives; the commonest cause for false positive referral was drusen in patients with background diabetic retinopathy. The sensitivity for identification of STDR was 76% (95% CI 70% to 81%) and specificity 95% (95% CI 95% to 96%). The likelihood ratio of a positive test indicating STDR was 16.54 (95% CI 14.17 to 19.23) and that of a negative test 0.25 (95% CI 0.20 to 0.32). The technical failure rate was 0.2%. CONCLUSIONS: Suitably trained and accredited community optometrists performed well when screening for diabetic retinopathy using slit-lamp biomicroscopy through a dilated pupil. This was facilitated by the use of simple grading and referral criteria. The sensitivity, positive likelihood ratio and specificity were high.