Quantification of anandamide and 2-arachidonoylglycerol plasma levels to examine potential influences of tetrahydrocannabinol application on the endocannabinoid system in humans

The effects of tetrahydrocannabinol (THC) and endogenous cannabinoids (endocannabinoids, ECs) are both mediated by activation of the cannabinoid receptors CB1 and CB2. Exogenous activation of these receptors by THC could therefore alter EC levels. We tested this hypothesis in healthy volunteers (n = 25) who received a large intravenous dose of THC (0.10 mg/kg). Effects on the EC system were quantified by serial measurements of plasma ECs after THC administration. Eleven blood samples were drawn during the first 5 h after THC administration and two more samples after 24 and 48 h. THC, its metabolites THC-OH (biologically active) and THC-COOH (non-active), and the ECs anandamide and 2-arachidonoylglycerol (2-AG) were quantified by liquid chromatography-mass spectrometry. EC-plasma levels showed a biphasic response after THC injection reaching maximal values at 30 min. Anandamide increased slightly from 0.58 ± 0.21 ng/ml at baseline to 0.64 ± 0.24 ng/ml (p < 0.05) and 2-AG from 7.60 ± 4.30 ng/ml to 9.50 ± 5.90 ng/ml (p < 0.05). After reaching maximal concentrations, EC plasma levels decreased markedly to a nadir of 300 min after THC administration (to 0.32 ± 0.15 ng/ml for anandamide and to 5.50 ± 3.01 ng/ml for 2-AG, p < 0.05). EC plasma concentrations returned to near baseline levels until 48 h after the experiment. THC (0.76 ± 0.16 ng/ml) and THC-OH (0.36 ± 0.17 ng/ml) were still measurable at 24 h and remained detectible until 48 h after THC administration. Although the underlying mechanism is not clear, high doses of intravenous THC appear to influence endogenous cannabinoid concentrations and presumably EC-signalling.

Transient Earth system responses to cumulative carbon dioxide emissions: linearities, uncertainties, and probabilities in an observation-constrained model ensemble

Information on the relationship between cumulative fossil CO2 emissions and multiple climate targets is essential to design emission mitigation and climate adaptation strategies. In this study, the transient response of a climate or environmental variable per trillion tonnes of CO2 emissions, termed TRE, is quantified for a set of impact-relevant climate variables and from a large set of multi-forcing scenarios extended to year 2300 towards stabilization. An  ∼ 1000-member ensemble of the Bern3D-LPJ carbon–climate model is applied and model outcomes are constrained by 26 physical and biogeochemical observational data sets in a Bayesian, Monte Carlo-type framework. Uncertainties in TRE estimates include both scenario uncertainty and model response uncertainty. Cumulative fossil emissions of 1000 Gt C result in a global mean surface air temperature change of 1.9 °C (68 % confidence interval (c.i.): 1.3 to 2.7 °C), a decrease in surface ocean pH of 0.19 (0.18 to 0.22), and a steric sea level rise of 20 cm (13 to 27 cm until 2300). Linearity between cumulative emissions and transient response is high for pH and reasonably high for surface air and sea surface temperatures, but less pronounced for changes in Atlantic meridional overturning, Southern Ocean and tropical surface water saturation with respect to biogenic structures of calcium carbonate, and carbon stocks in soils. The constrained model ensemble is also applied to determine the response to a pulse-like emission and in idealized CO2-only simulations. The transient climate response is constrained, primarily by long-term ocean heat observations, to 1.7 °C (68 % c.i.: 1.3 to 2.2 °C) and the equilibrium climate sensitivity to 2.9 °C (2.0 to 4.2 °C). This is consistent with results by CMIP5 models but inconsistent with recent studies that relied on short-term air temperature data affected by natural climate variability.

Sediments of Lake Vens (SW European Alps, France) record large-magnitude earthquake events

We studied sediment cores from Lake Vens (2,327 m asl), in the Tinée Valley of the SW Alps, to test the paleoseismic archive potential of the lake sediments in this particularly earthquake-sensitive area. The historical earthquake catalogue shows that moderate to strong earthquakes, with intensities of IX–X, have impacted the Southern Alps during the last millennium. Sedimentological (X-ray images, grain size distribution) and geochemical (major elements and organic matter) analyses show that Lake Vens sediments consist of a terrigenous, silty material (minerals and organic matter) sourced from the watershed and diatom frustules. A combination of X-ray images, grain-size distribution, major elements and magnetic properties shows the presence of six homogenite-type deposits interbedded in the sedimentary background. These sedimentological features are ascribed to sediment reworking and grain sorting caused by earthquake-generated seiches. The presence of microfaults that cross-cut the sediment supports the hypothesis of seismic deposits in this system. A preliminary sediment chronology is provided by 210Pb measurement and AMS 14C ages. According to the chronology, the most recent homogenite events are attributable to damaging historic earthquakes in AD 1887 (Ligure) and 1564 (Roquebillière). Hence, the Lake Vens sediment recorded large-magnitude earthquakes in the region and permits a preliminary estimate of recurrence time for such events of ~400 years.

Geometry and kinematics of the Roisan-Cignana Shear Zone, and the orogenic evolution of the Dent Blanche Tectonic System (Western Alps)

The Dent Blanche Tectonic System (DBTS) is a composite thrust sheet derived from the previously thinned passive Adriatic continental margin. A kilometric high-strain zone, the Roisan-Cignana Shear Zone (RCSZ) defines the major tectonic boundary within the DBTS and separates it into two subunits, the Dent Blanche s.s. nappe to the northwest and the Mont Mary nappe to the southeast. Within this shear zone, tectonic slices of Mesozoic and pre-Alpine meta-sediments became amalgamated with continental basement rocks of the Adriatic margin. The occurrence of high pressure assemblages along the contact between these tectonic slices indicates that the amalgamation occurred prior to or during the subduction process, at an early stage of the Alpine orogenic cycle. Detailed mapping, petrographic and structural analysis show that the Roisan-Cignana Shear Zone results from several superimposed Alpine structural and metamorphic stages. Subduction of the continental fragments is recorded by blueschist-facies deformation, whereas the Alpine collision is reflected by a greenschist facies overprint associated with the development of large-scale open folds. The postnappe evolution comprises the development of low-angle brittle faults, followed by large-scale folding (Vanzone phase) and finally brittle extensional faults. The RCSZ shows that fragments of continental crust had been torn off the passive continental margin prior to continental collision, thus recording the entire history of the orogenic cycle. The role of preceding Permo-Triassic lithospheric thinning, Jurassic rifting, and ablative subduction processes in controlling the removal of crustal fragments from the reactivated passive continental margin is discussed. Results of this study constrain the temporal sequence of the tectono-metamorphic processes involved in the assembly of the DBTS, but they also show limits on the interpretation. In particular it remains difficult to judge to what extent precollisional rifting at the Adriatic continental margin preconditioned the efficiency of convergent processes, i.e. accretion, subduction, and orogenic exhumation.

Cosmogenic 180W variations in meteorites and re-assessment of a possible 184Os–180W decay system

We measured tungsten (W) isotopes in 23 iron meteorites and the metal phase of the CB chondrite Gujba in order to ascertain if there is evidence for a large-scale nucleosynthetic heterogeneity in the p-process isotope 180W in the solar nebula as recently suggested by Schulz et al. (2013). We observed large excesses in 180W (up to ≈ 6 ε) in some irons. However, significant within-group variations in magmatic IIAB and IVB irons are not consistent with a nucleosynthetic origin, and the collateral effects on 180W from an s-deficit in IVB irons cannot explain the total variation. We present a new model for the combined effects of spallation and neutron capture reactions on 180W in iron meteorites and show that at least some of the observed within-group variability is explained by cosmic ray effects. Neutron capture causes burnout of 180W, whereas spallation reactions lead to positive shifts in 180W. These effects depend on the target composition and cosmic-ray exposure duration; spallation effects increase with Re/W and Os/W ratios in the target and with exposure age. The correlation of 180W/184W with Os/W ratios in iron meteorites results in part from spallogenic production of 180W rather than from 184Os decay, contrary to a recent study by Peters et al. (2014). Residual ε180W excesses after correction for an s-deficit and for cosmic ray effects may be due to ingrowth of 180W from 184Os decay, but the magnitude of this ingrowth is at least a factor of ≈2 smaller than previously suggested. These much smaller effects strongly limit the applicability of the putative 184Os-180W system to investigate geological problems.

Real-time simulation of nonequilibrium transport of magnetization in large open quantum spin systems driven by dissipation

Using quantum Monte Carlo, we study the nonequilibrium transport of magnetization in large open strongly correlated quantum spin-12 systems driven by purely dissipative processes that conserve the uniform or staggered magnetization, disregarding unitary Hamiltonian dynamics. We prepare both a low-temperature Heisenberg ferromagnet and an antiferromagnet in two parts of the system that are initially isolated from each other. We then bring the two subsystems in contact and study their real-time dissipative dynamics for different geometries. The flow of the uniform or staggered magnetization from one part of the system to the other is described by a diffusion equation that can be derived analytically.

Yellow laser light generation by frequency doubling of the output from a master oscillator fiber power amplifier system

We present a power-scalable approach for yellow laser-light generation based on standard Ytterbium (Yb) doped fibers. To force the cavity to lase at 1154 nm, far above the gain-maximum, measures must be taken to fulfill lasing condition and to suppress competing amplified spontaneous emission (ASE) in the high-gain region. To prove the principle we built a fiber-laser cavity and a fiber-amplifier both at 1154 nm. In between cavity and amplifier we suppressed the ASE by 70 dB using a fiber Bragg grating (FBG) based filter. Finally we demonstrated efficient single pass frequency doubling to 577 nm with a periodically poled lithium niobate crystal (PPLN). With our linearly polarized 1154 nm master oscillator power fiber amplifier (MOFA) system we achieved slope efficiencies of more than 15 % inside the cavity and 24 % with the fiber-amplifier. The frequency doubling followed the predicted optimal efficiency achievable with a PPLN crystal. So far we generated 1.5 W at 1154nm and 90 mW at 577 nm. Our MOFA approach for generation of 1154 nm laser radiation is power-scalable by using multi-stage amplifiers and large mode-area fibers and is therefore very promising for building a high power yellow laser-light source of several tens of Watt.

WEAVE: Efficient Geographical Routing in Large-Scale Networks

We propose WEAVE, a geographical 2D/3D routing protocol that maintains information on a small number of waypoints and checkpoints for forwarding packets to any destination. Nodes obtain the routing information from partial traces gathered in incoming packets and use a system of checkpoints along with the segments of routes to weave end-to-end paths close to the shortest ones. WEAVE does not generate any control traffic, it is suitable for routing in both 2D and 3D networks, and does not require any strong assumption on the underlying network graph such as the Unit Disk or a Planar Graph. WEAVE compares favorably with existing protocols in both testbed experiments and simulations.

Dithiothreitol triggers photooxidative stress and fragmentation of the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase in intact pea chloroplasts

In intact chloroplasts isolated from mature pea leaves (Pisum sativum L.), the large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) was rapidly fragmented into several products upon illumination in the presence of 1 mM dithiothreitol (DTT). Very similar effects on LSU stability could be observed when illuminated chloroplasts were poisoned with cyanide which, like DTT, inhibits important plastid antioxidant enzymes, or when a light-dependent hydroxyl radical-producing system was added to the incubation medium. Moreover, DTT-stimulated light degradation of LSU was markedly delayed in the presence of scavengers of active oxygen species (AOS). It is therefore suggested that light degradation of LSU in the presence of DTT is mainly due to inhibition of the chloroplast antioxidant defense system and the subsequent accumulation of AOS in intact organelles. When chloroplasts were isolated from nonsenescent or senescent leaves, LSU remained very stable upon incubation without DTT, indicating that the antioxidant system was still functional in the isolated chloroplasts during leaf ageing. Our data support the notion that AOS might be important for the degradation of Rubisco in vivo under oxidative stress.

A survey of the implementation status of environmental management systems in U.S. colleges and universities, and, An environmental management system implementation model for U.S. colleges and universities

A census of 925 U.S. colleges and universities offering masters and doctorate degrees was conducted in order to study the number of elements of an environmental management system as defined by ISO 14001 possessed by small, medium and large institutions. A 30% response rate was received with 273 responses included in the final data analysis. Overall, the number of ISO 14001 elements implemented among the 273 institutions ranged from 0 to 16, with a median of 12. There was no significant association between the number of elements implemented among institutions and the size of the institution (p = 0.18; Kruskal-Wallis test) or among USEPA regions (p = 0.12; Kruskal-Wallis test). The proportion of U.S. colleges and universities that reported having implemented a structured, comprehensive environmental management system, defined by answering yes to all 16 elements, was 10% (95% C.I. 6.6%–14.1%); however 38% (95% C.I. 32.0%–43.8%) reported that they had implemented a structured, comprehensive environmental management system, while 30.0% (95% C.I. 24.7%–35.9%) are planning to implement a comprehensive environmental management system within the next five years. Stratified analyses were performed by institution size, Carnegie Classification and job title. ^ The Osnabruck model, and another under development by the South Carolina Sustainable Universities Initiative, are the only two environmental management system models that have been proposed specifically for colleges and universities, although several guides are now available. The Environmental Management System Implementation Model for U.S. Colleges and Universities developed is an adaptation of the ISO 14001 standard and USEPA recommendations and has been tailored to U.S. colleges and universities for use in streamlining the implementation process. In using this implementation model created for the U.S. research and academic setting, it is hoped that these highly specialized institutions will be provided with a clearer and more cost-effective path towards the implementation of an EMS and greater compliance with local, state and federal environmental legislation. ^

Federally regulated institutional review boards: The aspects of a "model" IRB---Is the current system in need of a tune up or complete overhaul?

Institutional Review Boards (IRBs) are the primary gatekeepers for the protection of ethical standards of federally regulated research on human subjects in this country. This paper focuses on what general, broad measures that may be instituted or enhanced to exemplify a "model IRB". This is done by examining the current regulatory standards of federally regulated IRBs, not private or commercial boards, and how many of those standards have been found either inadequate or not generally understood or followed. The analysis includes suggestions on how to bring about changes in order to make the IRB process more efficient, less subject to litigation, and create standardized educational protocols for members. The paper also considers how to include better oversight for multi-center research, increased centralization of IRBs, utilization of Data Safety Monitoring Boards when necessary, payment for research protocol review, voluntary accreditation, and the institution of evaluation/quality assurance programs. ^ This is a policy study utilizing secondary analysis of publicly available data. Therefore, the research for this paper focuses on scholarly medical/legal journals, web information from the Department of Health and Human Services, Federal Drug Administration, and the Office of the Inspector General, Accreditation Programs, law review articles, and current regulations applicable to the relevant portions of the paper. ^ Two issues are found to be consistently cited by the literature as major concerns. One is a need for basic, standardized educational requirements across all IRBs and its members, and secondly, much stricter and more informed management of continuing research. There is no federally regulated formal education system currently in place for IRB members, except for certain NIH-based trials. Also, IRBs are not keeping up with research once a study has begun, and although regulated to do so, it does not appear to be a great priority. This is the area most in danger of increased litigation. Other issues such as voluntary accreditation and outcomes evaluation are slowing gaining steam as the processes are becoming more available and more sought after, such as JCAHO accrediting of hospitals. ^ Adopting the principles discussed in this paper should promote better use of a local IRBs time, money, and expertise for protecting the vulnerable population in their care. Without further improvements to the system, there is concern that private and commercial IRBs will attempt to create a monopoly on much of the clinical research in the future as they are not as heavily regulated and can therefore offer companies quicker and more convenient reviews. IRBs need to consider the advantages of charging for their unique and important services as a cost of doing business. More importantly, there must be a minimum standard of education for all IRB members in the area of the ethical standards of human research and a greater emphasis placed on the follow-up of ongoing research as this is the most critical time for study participants and may soon lead to the largest area for litigation. Additionally, there should be a centralized IRB for multi-site trials or a study website with important information affecting the trial in real time. There needs to be development of standards and metrics to assess the performance of the IRBs for quality assurance and outcome evaluations. The boards should not be content to run the business of human subjects' research without determining how well that function is actually being carried out. It is important that federally regulated IRBs provide excellence in human research and promote those values most important to the public at large.^

Financial impact of the Medicare prospective payment system on long term acute care hospitals

Objective. Long Term Acute Care Hospitals (LTACs) are subject to Medicare rules because they accept Medicare and Medicaid patients. In October 2002, Medicare changed the LTAC reimbursement formulas, from a cost basis system to a Prospective Payment System (PPS). This study examines whether the PPS has negatively affected the financial performance of the LTAC hospitals in the period following the reimbursement change (2003-2006), as compared to the period prior to the change (1999-2003), and if so, to what extent. This study will also examine whether the PPS has resulted in a decreased average patient length of stay (LOS) in the LTAC hospitals for the period of 2003-2006 as compared to the prior period of 1999-2003, and if so, to what extent. ^ Methods. The study group consists of two large LTAC hospital systems, Kindred Healthcare Inc. and Select Specialty Hospitals of Select Medical Corporation. Financial data and operational indicators were reviewed, tabulated and dichotomized into two groups, covering the two periods: 1999-2002 and 2003-2006. The financial data included net annual revenues, net income, revenue per patient per day and profit margins. It was hypothesized that the profit margins for the LTAC hospitals were reduced because of the new PPS. Operational indicators, such as annual admissions, annual patient days, and average LOS were analyzed. It was hypothesized that LOS for the LTAC hospitals would have decreased. Case mix index, defined as the weighted average of patients’ DRGs for each hospital system, was not available to cast more light on the direction of LOS. ^ Results. This assessment found that the negative financial impacts did not materialize; instead, financial performance improved during the PPS period (2003-2006). The income margin percentage under the PPS increased for Kindred by 24%, and for Select by 77%. Thus, the study’s working hypothesis of reduced income margins for the LTACs under the PPS was contradicted. As to the average patient length of stay, LOS decreased from 34.7 days to 29.4 days for Kindred, and from 30.5 days to 25.3 days for Select. Thus, on the issue of LTAC shorter length of stay, the study’s working hypothesis was confirmed. ^ Conclusion. Overall, there was no negative financial effect on the LTAC hospitals during the period of 2003-2006 following Medicare implementation of the PPS in October 2002. On the contrary, the income margins improved significantly. ^ During the same period, LOS decreased following the implementation of the PPS. This was consistent with the LTAC hospitals’ pursuit of financial incentives.^

Financial impact of the Medicare prospective payment system on long term acute care hospitals

Objective. Long Term Acute Care Hospitals (LTACs) are subject to Medicare rules because they accept Medicare and Medicaid patients. In October 2002, Medicare changed the LTAC reimbursement formulas, from a cost basis system to a Prospective Payment System (PPS). This study examines whether the PPS has negatively affected the financial performance of the LTAC hospitals in the period following the reimbursement change (2003–2006), as compared to the period prior to the change (1999–2003), and if so, to what extent. This study will also examine whether the PPS has resulted in a decreased average patient length of stay (LOS) in the LTAC hospitals for the period of 2003–2006 as compared to the prior period of 1999-2003, and if so, to what extent. ^ Methods. The study group consists of two large LTAC hospital systems, Kindred Healthcare Inc. and Select Specialty Hospitals of Select Medical Corporation. Financial data and operational indicators were reviewed, tabulated and dichotomized into two groups, covering the two periods: 1999–2002 and 2003–2006. The financial data included net annual revenues, net income, revenue per patient per day and profit margins. It was hypothesized that the profit margins for the LTAC hospitals were reduced because of the new PPS. Operational indicators, such as annual admissions, annual patient days, and average LOS were analyzed. It was hypothesized that LOS for the LTAC hospitals would have decreased. Case mix index, defined as the weighted average of patients’ DRGs for each hospital system, was not available to cast more light on the direction of LOS. ^ Results. This assessment found that the negative financial impacts did not materialize; instead, financial performance improved during the PPS period (2003–2006). The income margin percentage under the PPS increased for Kindred by 24%, and for Select by 77%. Thus, the study’s working hypothesis of reduced income margins for the LTACs under the PPS was contradicted. As to the average patient length of stay, LOS decreased from 34.7 days to 29.4 days for Kindred, and from 30.5 days to 25.3 days for Select. Thus, on the issue of LTAC shorter length of stay, the study’s working hypothesis was confirmed. ^ Conclusion. Overall, there was no negative financial effect on the LTAC hospitals during the period of 2003–2006 following Medicare implementation of the PPS in October 2002. On the contrary, the income margins improved significantly. ^ During the same period, LOS decreased following the implementation of the PPS. This was consistent with the LTAC hospitals’ pursuit of financial incentives. ^

Prevalence and determinants of colonic polyps in children undergoing colonoscopy: A large hospital-based cross-sectional study

Background. Colorectal polyps are abnormal growths in the wall of the colon including the rectum. The study aims to estimate the prevalence and type of colonic polyps in children undergoing colonoscopic examination at Texas Children's Hospital (TCH) in Houston, Texas during 2000-2007. Also, to examine the factors associated with colonic polyps and the potential determinants of colonic polyps in children undergoing colonoscopy and compare those who had colonic polyps with those who did not on colonoscopy, and determine the significant risk factors of colonic polyps in these children. ^ Methods. We conducted a cross sectional study to analyze data collected at TCH. We obtained demographic, clinical, and histopathology information on consecutive patients who underwent colonoscopy during 2000-2007 from endoscopic records contained in the PEDS-CORI registry (Pediatric Endoscopy Database System-Clinical Outcomes Research Initiative), and abstracted data from the accompanying histopathology reports. ^ Results. We identified 2,693-unique patients, under 18 years of age, who underwent colonoscopy. Approximately 65.5% were white non-Hispanic, and 10.8% African-American. The mean age was 8.7 years and 51.8% were female patients. Polyps were present in 174 patients (6.5%). The most common two histological types were juvenile (60.6%), inflammatory (17.4%). We found that the prevalence of polyps was higher in younger aged children (12.9% in 0-5 years) than in older aged children (4% in 15-17 years), and slightly higher in males than in females (7.9% and 5.4% respectively). For males only, the odds of polyps were statistically significantly higher in Blacks and Hispanics compared to white non Hispanics (OR of 2.2 and 2.1, respectively, and 95% CI of 1.3, 3.9 and 1.3, 3.5 respectively). The indications for colonoscopy were different for children with polyps compared to those without polyps, i.e., 47.0% vs. 19.8% respectively for lower GI bleeding, 2.7% vs. 21.4% respectively for abdominal pain/bloating, and, or 0.9% vs. 9.6% respectively for diarrhea. ^ Conclusion. Colorectal polyps occur in about 1 in 15 children and adolescents undergoing first colonoscopy. The demographic variable of younger age is strongly associated with having polyps irrespective of ethnicity. Lower GI bleeding is strongly related to the presence of colorectal polyps in children and adolescents undergoing colonoscopy.^

Performance enhancement of large industrial wastewater stabilization ponds

A 6-month-long, bench-scale simulation of an industrial wastewater stabilization pond (WSP) system was conducted to evaluate responses to several potential performance-enhancing treatments. The industrial WSP system consists of an anaerobic primary (1ry) WSP treating high-strength wastewater, followed by facultative secondary (2ry) and aerobic tertiary (3ry) WSPs in series treating lower-strength wastewater. The 1ry WSP was simulated with four glass aquaria which were fed with wastewater from the actual WSP system. The treatments examined were phosphorus supplementation (PHOS), phosphorus supplementation with pH control (PHOS+ALK), and phosphorus supplementation with pH control and effluent recycle (PHOS+ALK+RCY). The supplementary phosphorus treatment alone did not yield any significant change versus the CONTROL 1ry model pond. The average carbon to phosphorus ratio of the feed wastewater received from the WSP system was already 100:0.019 (i.e., 2,100 mg/l: 0.4 mg/l). The pH-control treatments (PHOS+ALK and PHOS+ALK+RCY) produced significant results, with 9 to 12 percent more total organic carbon (TOC) removal, 43 percent more volatile organic acid (VOA) generation, 78 percent more 2-ethoxyethanol and 14 percent more bis(2-chloroethyl)ether removal, and from 100- to 10,000-fold increases in bacterial enzyme activity and heterotrophic bacterial numbers. Recycling a 10-percent portion of the effluent yielded less variability for certain physicochemical parameters in the PHOS+ALK+RCY 1ry model pond, but overall there was no statistically-detectable improvement in performance versus no recycle. The 2ry and 3ry WSPs were also simulated in the laboratory to monitor the effect and fate of increased phosphorus loadings, as might occur if supplemental phosphorus were added to the 1ry WSP. Noticeable increases in algal growth were observed at feed phosphorus concentrations of 0.5 mg/l; however, there were no significant changes in the monitored physicochemical parameters. The effluent phosphorus concentrations from both the 2ry and 3ry model ponds did increase notably when feed phosphorus concentrations were increased from 0.5 to 1.0 mg/l. ^