Cavitation Events in Thuja occidentalis L.? : Utrasonic Acoustic Emissions from the Sapwood Can Be Measured

Ultrasonic acoustic emissions (AE) in the frequency range of 0.1 to 1 megahertz appear to originate in the sapwood of Thuja occidentalis L. The AE are vibrations of an impulsive nature. The vibrations can be transduced to a voltage waveform and amplified. The vibrations of each AE event begin at a large amplitude which decays over 20 to 100 microseconds. Strong circumstantial evidence indicates that the ultrasonic AE result from cavitation events because: (a) they occur only when the xylem pressure potential Ψ_xp is more negative than a threshold level of about —1 megapascal; (b) the rate of AE events increases as Ψ_xp decreases and when the net rate of water loss increases; (c) the AE can be stopped by raising Ψ_xp above —1 megapascal. Ultrasonic AE have been measured in whole terminal shoots allowed to dry in the laboratory, in isolated pieces of sapwood as they dried in the laboratory, and in whole terminal shoots in a pressure bomb when Ψ_xp was decreased by lowering the gas pressure in the pressure bomb.     

Ultrasonic acoustic emissions from the sapwood of cedar and hemlock : an examination of three hypotheses regarding cavitations

Measurements are reported of ultrasonic acoustic emissions (AEs) measured from sapwood samples of Thuja occidentalis L. and Tsuga canadensis (L.) Carr. during air dehydration. The measurements were undertaken to test the following three hypotheses: (a) Each cavitation event produces one ultrasonic AE. (b) Large tracheids are more likely to cavitate than small tracheids. (c) When stem water potentials are >−0.4 MPa, a significant fraction of the water content of sapwood is held by `capillary forces.' The last two hypotheses were recently discussed at length by M. H. Zimmermann. Experimental evidence consistent with all three hypotheses was obtained. The evidence for each hypothesis respectively is: (a) the cumulative number of AEs nearly equals the number of tracheids in small samples; (b) more water is lost per AE event at the beginning of the dehydration process than at the end, and (c) sapwood samples dehydrated from an initial water potential of 0 MPa lost significantly more water before AEs started than lost by samples dehydrated from an initial water potential of about −0.4 MPa. The extra water held by fully hydrated sapwood samples may have been capillary water as defined by Zimmerman.

We also report an improved method for the measurement of the `intensity' of ultrasonic AEs. Intensity is defined here as the area under the positive spikes of the AE signal (plotted as voltage versus time). This method was applied to produce a frequency histogram of the number of AEs versus intensity. A large fraction of the total number of AEs were of low intensity even in small samples (4 mm diameter by 10 mm length). This suggests that the effective `listening distance' for most AEs was less than 5 to 10 mm.

     

Detection of xylem cavitation in field-grown pine trees using the acoustic emission technique

The relationship between the ultrasonic acoustic emission (AE) and the needle water potential in field-grown Japanese black pine,Pinus thunbergii, and excised-pine shoots was investigated in summer. The AE technique was employed as a reliable indicator of cavitation events in the water columns of xylem tracheids even under field conditions. In excised shoots. AE events detected when the needle water potential fell below about-0.9 MPa. In the case of field-grown pine trees, however, relatively few AE event were detected when needle water potential was lower than-0.9 MPa. This suggests that the occurrence of cavitation events in Japanese black pine growing under field conditions is comparatively rare, even in summer.     

The Measurement and Interpretation of Ultrasound from Woody Stems

A system for detecting and counting ultrasonic acoustic emissions(AEs) from woody stems in the waveband of 0.1–1.0 MHzis described. AEs from small pieces of stems of Mains sylvestrisand Chamaecyparis lawsoniana occurred up to a rate of 6000 min^–1,and could be related to the water loss as the stems dried. AEsdid not occur randomly, but were aggregated. Each event is interpretedas a single cavitation occurring in the water within a tracheidor fibre. AEs could be temporarily stopped by rewetting thetissue or cutting it to release tension. From knowledge of thenumber of cells in the stems, the fraction of total counts pernumber of tracheids or fibres present in the stem was calculated.This was found to be less than 0.16. One reason why this fractionis so low is that AEs may occur simultaneously; it is also probablethat some AEs emit energy outside the waveband studied. Eventhough the fraction of AEs recorded is low, this instrumentcould prove to be a very powerful tool for investigating theoccurrence of cavitation in woody stems. Key words: Ultrasound, Cavitation, Wood     

Induction of laccases in Trametes versicolor by aqueous wood extracts

The induction of laccase isoforms in Trametes versicolor HEMIM-9 by aqueous extracts (AE) from softwood and hardwood was studied. Samples of sawdust of Pinus sp., Cedrela sp., and Quercus sp. were boiled in water to obtain AE. Different volumes of each AE were added to fungal cultures to determine the amount of AE needed for the induction experiments. Laccase activity was assayed every 24 h for 15 days. The addition of each AE (50 to 150 μl) to the fungal cultures increased laccase production compared to the control (0.42 ± 0.01 U ml^?1). The highest laccase activities detected were 1.92 ± 0.15 U ml^?1 (pine), 1.87 ± 0.26 U ml^?1 (cedar), and 1.56 ± 0.34 U ml^?1 (oak); laccase productivities were also significantly increased. Larger volumes of any AE inhibited mycelial growth. Electrophoretic analysis revealed two laccase bands (lcc1 and lcc2) for all the treatments. However, when lcc2 was analyzed by isoelectric focusing, inducer-dependent isoform patterns composed of three (pine AE), four (oak AE), and six laccase bands (cedar AE) were observed. Thus, AE from softwood and hardwood had induction effects in T. versicolor HEMIM-9, as indicated by the increase in laccase activity and different isoform patterns. All of the enzymatic extracts were able to decolorize the dye Orange II. Dye decolorization was mainly influenced by pH. The optimum pH for decolorization was pH 5 (85 %), followed by pH 7 (50 %) and pH 3 (15 %). No significant differences in the dye decolorizing capacity were detected between the control and the differentially induced laccase extracts (oak, pine and cedar). This could be due to the catalytic activities of isoforms with pI 5.4 and 5.8, which were detected under all induction conditions.     

Gravitropism in Higher Plant Shoots : II. Dimensional and Pressure Changes during Stem Bending

Dimensional changes during gravitropic bending of cocklebur (Xanthium strumarium L.) dicot stems were measured using techniques of stereo photogrammetry. The differential growth is from an increased growth rate on the bottom of the stem and a stopping or contraction of the top.

Contraction of the top was especially evident upon release and immediate bending of horizontal stems that had been restrained between stiff wires for 36 hours. The energy for this could have been stored in both the top and bottom, since the bottom elongated, and the top contracted.

Forces developed during bending were measured by fastening a stem tip to the end of a bar with attached strain gauges and recording electrical output from the strain gauges. Restrained mature cocklebur stems continued to accumulate potential energy for bending for about 120 hours, after which the recorded force reached a maximum.

Pressures within castor bean (Ricinus communis L.) stems were also measured with 3.5-millimeter diameter pressure transducers. As expected, the pressure on the bottom of the restrained plants increased with time; pressures decreased in vertical controls, tops of restrained stems, and bottoms of free-bending stems. Pressures increased in tops of free-bending stems. When restrained plants were released, pressure on the bottom decreased and pressure on the top increased. Results suggest a possible role for cell contraction in the top of stems bending upward in response to gravity.

     

Characterization and propagation of acoustic emission signals in woody plants: towards an improved acoustic emission counter

Abstract. The physics of ultrasonic acoustic emissions (AEs) was investigated for AE transmission through wood and transducers. The physical properties measured were velocity, attenuation and frequency composition of AEs produced by two sources: cavitation events in xylem and pencil lead breaks. The authors also measured the relative sensitivity of various combinations of ultrasound transducers and amplifiers to aid in the selection of a measuring system optimized for cavitation detection in woody plants. Some of the authors' conclusions are: (1) Softwoods ( Thuja, Pinus ) attenuate AEs more rapidly than hardwoods (maple, birch). (2) The velocity of AEs in wood exceeds that measured by others in water so the main medium of AE transmission must be the cellulose. (3) The strongest frequencies of AEs are in the range of 100–300 kHz. (4) Cavitation-induced AEs tend to shift to higher frequency as wood dehydration progresses. (5) One cannot determine the locus of origin of AEs from its frequency composition. (6) The frequency composition of the acoustic emissions probably cannot be determined at all with the sensors used because of their tendency to 'ring'. The data collected in this paper were used to aid in the design of an improved AE counter having a seven-fold increase in signal to noise ratio compared to counters previously used in our laboratory. The improved counter, model 4615 Drought Stress Monitor, is now commercially available from Physical Acoustics Corp., Princeton, NJ, U.S.A.     

Direct measurement of xylem pressure in leaves of intact maize plants. A test of the cohesion-tension theory taking hydraulic architecture into consideration

The water relations of maize (Zea mays L. cv Helix) were documented in terms of hydraulic architecture and xylem pressure. A high-pressure flowmeter was used to characterize the hydraulic resistances of the root, stalk, and leaves. Xylem pressure measurements were made with a Scholander-Hammel pressure bomb and with a cell pressure probe. Evaporation rates were measured by gas exchange and by gravimetric measurements. Xylem pressure was altered by changing the light intensity, by controlling irrigation, or by gas pressure applied to the soil mass (using a root pressure bomb). Xylem pressure measured by the cell pressure probe and by the pressure bomb agreed over the entire measured range of 0 to −0.7 MPa. Experiments were consistent with the cohesion-tension theory. Xylem pressure changed rapidly and reversibly with changes in light intensity and root-bomb pressure. Increasing the root-bomb pressure increased the evaporation rate slightly when xylem pressure was negative and increased water flow rate through the shoots dramatically when xylem pressure was positive and guttation was observed. The hydraulic architecture model could predict all observed changes in water flow rate and xylem. We measured the cavitation threshold for oil- and water-filled pressure probes and provide some suggestions for improvement.     

Development of Photosynthetic Activity following Anaerobic Germination in Rice-Mimic Grass (Echinochloa crus-galli var oryzicola)

Shoots of anaerobically germinated Echinochloa crus-galli var oryzicola are nonpigmented whether germinated in light or dark, and chlorophyll synthesis is minimal for the first 12 to 18 hours of greening after exposure to ambient conditions. When chlorophyll development is compared between greening anoxic and etiolated shoots, there is a 100-fold difference in chlorophyll levels at 8 hours, an 8-fold difference at 24 hours, but roughly equal amounts at 60 hours. The chlorophyll a/b ratio approaches 3 earlier in greening anoxic shoots than in greening etiolated shoots, relative to total chlorophyll. The long lag in chlorophyll synthesis can be shortened by giving dark-grown anoxic shoots a 24-hour midtreatment of air before light.

Development of photosynthetic activity in etiolated shoots, determined by CO₂ gas exchange, ¹⁴CO₂ uptake, and activity of carboxylating enzymes closely parallels development of chlorophylls. However, development of photosynthetic capability in greening anoxic shoots does not parallel chlorophyll development; ability to fix carbon lags behind chlorophyll synthesis. A reason for this lag is the very low activity of RuBP carboxylase during the first 36 hours of greening in anoxic shoots. The activity of phosphoenolpyruvate carboxylase is also delayed, but its kinetics more closely match those of chlorophyll development.

     

Ontology-Based Combinatorial Comparative Analysis of Adverse Events Associated with Killed and Live Influenza Vaccines

Vaccine adverse events (VAEs) are adverse bodily changes occurring after vaccination. Understanding the adverse event (AE) profiles is a crucial step to identify serious AEs. Two different types of seasonal influenza vaccines have been used on the market: trivalent (killed) inactivated influenza vaccine (TIV) and trivalent live attenuated influenza vaccine (LAIV). Different adverse event profiles induced by these two groups of seasonal influenza vaccines were studied based on the data drawn from the CDC Vaccine Adverse Event Report System (VAERS). Extracted from VAERS were 37,621 AE reports for four TIVs (Afluria, Fluarix, Fluvirin, and Fluzone) and 3,707 AE reports for the only LAIV (FluMist). The AE report data were analyzed by a novel combinatorial, ontology-based detection of AE method (CODAE). CODAE detects AEs using Proportional Reporting Ratio (PRR), Chi-square significance test, and base level filtration, and groups identified AEs by ontology-based hierarchical classification. In total, 48 TIV-enriched and 68 LAIV-enriched AEs were identified (PRR>2, Chi-square score >4, and the number of cases >0.2% of total reports). These AE terms were classified using the Ontology of Adverse Events (OAE), MedDRA, and SNOMED-CT. The OAE method provided better classification results than the two other methods. Thirteen out of 48 TIV-enriched AEs were related to neurological and muscular processing such as paralysis, movement disorders, and muscular weakness. In contrast, 15 out of 68 LAIV-enriched AEs were associated with inflammatory response and respiratory system disorders. There were evidences of two severe adverse events (Guillain-Barre Syndrome and paralysis) present in TIV. Although these severe adverse events were at low incidence rate, they were found to be more significantly enriched in TIV-vaccinated patients than LAIV-vaccinated patients. Therefore, our novel combinatorial bioinformatics analysis discovered that LAIV had lower chance of inducing these two severe adverse events than TIV. In addition, our meta-analysis found that all previously reported positive correlation between GBS and influenza vaccine immunization were based on trivalent influenza vaccines instead of monovalent influenza vaccines.     

Termination of nutrient import and development of vein loading capacity in albino tobacco leaves

The sink-source conversion in developing leaves of tobacco (Nicotiana tabacum L.) was studied to determine whether import termination is caused by the onset of export or is related to achievement of positive carbon balance. Albino shoots were grown in vitro and grafted to detopped stems of green tobacco plants. Termination of import was studied by providing mature leaves of the stock plant with ¹⁴CO₂ and detecting the presence of labeled nutrient in developing albino leaves by whole-leaf autoradiography. In albino leaves, import terminated progressively in the basipetal direction at the same stage of development as in leaves of green shoots. Starch was not present in the plastids of mesophyll cells of mature albino leaves but starch was synthesized when discs were cut from these leaves and incubated on 3 millimolar sucrose. Import ceased progressively in developing green leaves even when photosynthesis was prevented by darkening. It was concluded that cessation of import does not require achievement of positive carbon balance and is not the direct result of export initiation.

To determine whether vein loading capacity develops in albino leaves, discs were cut from mature leaves and floated on [¹⁴C]sucrose solution. Uptake of label into the veins was detected by autoradiography and this uptake was sensitive to the phloem loading inhibitor p-chloromercuribenzenesulfonic acid. However, the amount of label taken up by veins in albino leaves was less than that taken up by veins of mature green leaves.

     

Formation of biphenyl and dibenzofuran phytoalexins in the transition zones of fire blight-infected stems of Malus domestica cv. ‘Holsteiner Cox’ and Pyrus communis cv. ‘Conference’

In the rosaceous subtribe Pyrinae (formerly subfamily Maloideae), pathogen attack leads to formation of biphenyls and dibenzofurans. Accumulation of these phytoalexins was studied in greenhouse-grown grafted shoots of Malus domestica cv. ‘Holsteiner Cox’ and Pyrus communis cv. ‘Conference’ after inoculation with the fire blight bacterium, Erwinia amylovora. No phytoalexins were found in leaves. However, both classes of defence compounds were detected in the transition zone of stems. The flanking stem segments above and below this zone, which were necrotic and healthy, respectively, were devoid of detectable phytoalexins. The transition zone of apple stems contained the biphenyls 3-hydroxy-5-methoxyaucuparin, aucuparin, noraucuparin and 2′-hydroxyaucuparin and the dibenzofurans eriobofuran and noreriobofuran. In pear, aucuparin, 2′-hydroxyaucuparin, noreriobofuran and in addition 3,4,5-trimethoxybiphenyl were detected. The total phytoalexin content in the transition zone of pear was 25 times lower than that in apple. Leaves and stems of mock-inoculated apple and pear shoots lacked phytoalexins. A number of biphenyls and dibenzofurans were tested for their in vitro antibacterial activity against some Erwinia amylovora strains. The most efficient compound was 3,5-dihydroxybiphenyl (MIC = 115 μg/ml), the immediate product of biphenyl synthase which initiates phytoalexin biosynthesis.     

Fusion of the inducible promoter of the PR-1a gene to the Activator transposase gene can transactive excision of a non-autonomous transposable element by external and by internal stimuli

The open reading frame coding for the transposase gene of the maize transposon Activator (Ac) was expressed in transgenic tobacco plants under the control of the promoter of the inducible gene for pathogenesis-related protein 1a (PR-1a). Excision of a non-autonomous transposable element (Ds) from chimeric β-glucuronidase (GUS) and luciferase reporter gene constructs was employed to analyze the induction of the Ac transposase by external and by internal stimuli. Applying the GUS histochemical assay, Ds excision events were detected in leaves, stems, and roots after treatment of regenerating shoots with salicylic acid (SA). Varying the SA induction procedure led to different Ds excision patterns in leaves and in roots. Furthermore, Ds excision events were also observed in non-treated, older transgenic plants in the green leaves, but not in germinal cells. Thus, the PR-1a promoter/Ac transposase gene fusion, together with the improved methods for induction of this chimeric gene, may provide a valuable tool for studying basic mechanisms of Ac transposition and for developing modified transposable element systems suitable for gene tagging in higher plants.     

Development and Distribution of a Lectin from the Stems and Leaves of Dolichos biflorus

The stems and leaves of the Dolichos biflorus plant contain a lectin that cross-reacts with antiserum against the seed lectin. This cross-reactive material (CRM) was followed during early seedling growth, stem elongation, and seed development using a specific radioimmunoassay.

No CRM was detected in developing seeds, but very low levels were found in dormant and imbibed seeds. As germination proceeds, the CRM accumulates at the apex of both etiolated and green seedlings in the epicotyl and leaves. Lower amounts of CRM are found in the cotyledons and hypocotyl, but no CRM was detected in the roots.

The amount of CRM in the first and second stem internodes increases during elongation and gradually declines after the completion of elongation. Approximately 80% of the CRM in the stems of 19-day-old Dolichos biflorus plants is associated with the elongating tissues. These results are discussed with respect to the possible roles of lectins in plants.

     

A Survey of the FDA's AERS Database Regarding Muscle and Tendon Adverse Events Linked to the Statin Drug Class

Background

Cholesterol management drugs known as statins are widely used and often well tolerated; however, a variety of muscle-related side effects can arise. These adverse events (AEs) can have serious impact, and form a significant barrier to therapy adherence. Surveillance of post-marketing AEs is of vital importance to understand real-world AEs and reporting differences between individual statin drugs. We conducted a review of post-approval muscle and tendon AE reports in association with statin use, to assess differences within the drug class.

Methods

We analyzed all case reports from the FDA AE Reporting System (AERS) database linking muscle-related AEs to statin use (07/01/2005–03/31/2011). Drugs examined were: atorvastatin, simvastatin, lovastatin, pravastatin, rosuvastatin, and fluvastatin.

Results

Relative risk rates for rosuvastatin were consistently higher than other statins. Atorvastatin and simvastatin showed intermediate risks, while pravastatin and lovastatin appeared to have the lowest risk rates. Relative risk of muscle-related AEs, therefore, approximately tracked with per milligram LDL-lowering potency, with fluvastatin an apparent exception. Incorporating all muscle categories, rates for atorvastatin, simvastatin, pravastatin, and lovastatin were, respectively, 55%, 26%, 17%, and 7.5% as high, as rosuvastatin, approximately tracking per milligram potency (Rosuvastatin>Atorvastatin>Simvastatin>Pravastatin≈Lovastatin) and comporting with findings of other studies. Relative potency, therefore, appears to be a fundamental predictor of muscle-related AE risk, with fluvastatin, the least potent statin, an apparent exception (risk 74% vs rosuvastatin).

Interpretation

AE reporting rates differed strikingly for drugs within the statin class, with relative reporting aligning substantially with potency. The data presented in this report offer important reference points for the selection of statins for cholesterol management in general and, especially, for the rechallenge of patients who have experienced muscle-related AEs (for whom agents of lower expected potency should be preferred).     

Long-Term Effects of Intermittent IL-2 in HIV Infection: Extended Follow-Up of the INSIGHT STALWART Study

Background

The Study of Aldesleukin with and without Antiretroviral Therapy (STALWART) was designed to evaluate whether intermittent IL-2 alone or with peri-cycle ART increased CD4+ cell counts (and so delayed initiation of ART) in HIV infected individuals having ≥300 CD4+ cells/mm³ compared to untreated controls. When the results of two large clinical trials, ESPRIT and SILCAAT, showed no clinical benefit from IL-2 therapy, IL-2 administration was halted in STALWART. Because IL-2 recipients in STALWART experienced a greater number of opportunistic disease (OD) or death and adverse events (AEs), participants were asked to consent to an extended follow-up phase in order to assess persistence of IL-2 effects.

Methodology

Participants in this study were followed for clinical events and AEs every 4 months for 24 months. Unadjusted Cox proportional hazards models were used to summarize death, death or first OD event, and first grade 3 or 4 AE.

Principal Findings

A total of 267 persons were enrolled in STALWART (176 randomized to the IL-2 arms and 91 to the no therapy arm); 142 individuals in the IL-2 group and 80 controls agreed to enter the extended follow-up study. Initiation of continuous ART was delayed in the IL-2 groups, but once started, resulted in similar CD4+ cell and viral load responses compared to controls. The hazard ratios (95% CI) for IL-2 versus control during the extension phase for death or OD, grade 3 or 4 AE, and grade 4 AE were 1.45 (0.38, 5.45), 0.43 (0.24, 1.63) and 0.20 (0.04, 1.03), respectively. The hazard ratios for the AE outcomes were significantly lower during the extension than during the main study.

Conclusions

Adverse events associated with IL-2 cycling did not persist upon discontinuation of IL-2. The use of IL-2 did not impact the subsequent response to initiation of cART.     

Corona is required for higher-order assembly of transverse filaments into full-length synaptonemal complex in Drosophila oocytes

The synaptonemal complex (SC) is an intricate structure that forms between homologous chromosomes early during the meiotic prophase, where it mediates homolog pairing interactions and promotes the formation of genetic exchanges. In Drosophila melanogaster, C(3)G protein forms the transverse filaments (TFs) of the SC. The N termini of C(3)G homodimers localize to the Central Element (CE) of the SC, while the C-termini of C(3)G connect the TFs to the chromosomes via associations with the axial elements/lateral elements (AEs/LEs) of the SC. Here, we show that the Drosophila protein Corona (CONA) co-localizes with C(3)G in a mutually dependent fashion and is required for the polymerization of C(3)G into mature thread-like structures, in the context both of paired homologous chromosomes and of C(3)G polycomplexes that lack AEs/LEs. Although AEs assemble in cona oocytes, they exhibit defects that are characteristic of c(3)G mutant oocytes, including failure of AE alignment and synapsis. These results demonstrate that CONA, which does not contain a coiled coil domain, is required for the stable ‘zippering’ of TFs to form the central region of the Drosophila SC. We speculate that CONA's role in SC formation may be similar to that of the mammalian CE proteins SYCE2 and TEX12. However, the observation that AE alignment and pairing occurs in Tex12 and Syce2 mutant meiocytes but not in cona oocytes suggests that the SC plays a more critical role in the stable association of homologs in Drosophila than it does in mammalian cells.     

Adverse events among medical patients after discharge from hospital

BackgroundAdverse events (AEs) are adverse outcomes caused by medical care. Several studies have indicated that a substantial number of patients experience AEs before or during hospitalization. However, few data describe AEs after hospital discharge. We determined the incidence, severity, preventability and ameliorability of AEs in patients discharged from the general internal medicine service of a Canadian hospital.MethodsAt a multisite Canadian teaching hospital, we prospectively studied patients who were consecutively discharged home or to a seniors'' residence from the general internal medicine service during a 14-week interval in 2002. We used telephone interview and chart review to identify outcomes after discharge. Two physicians independently reviewed each outcome to determine if the patient experienced an AE. The severity, preventability and ameliorability of all AEs were classified.ResultsDuring the study period, outcomes were determined for 328 of the 361 eligible patients, who averaged 71 years of age (interquartile range 54–81 years). After discharge, 76 of the 328 patients experienced at least 1 AE (overall incidence 23%, 95% confidence interval [CI] 19%–28%). The AE severity ranged from symptoms only (68% of the AEs) or symptoms associated with a nonpermanent disability (25%) to permanent disability (3%) or death (3%). The most common AEs were adverse drug events (72%), therapeutic errors (16%) and nosocomial infections (11%). Of the 76 patients, 38 had an AE that was either preventable or ameliorable (overall incidence 12%, 95% CI 9%–16%).InterpretationApproximately one-quarter of patients in our study had an AE after hospital discharge, and half of the AEs were preventable or ameliorable.The Institute of Medicine report Crossing the quality chasm identifies patient safety as a prerequisite to high-quality care.¹ The need to improve safety is highlighted by research showing that hospitalized patients have a high risk of adverse outcomes resulting from treatment. For example, the Harvard Medical Practice Study found that adverse events (AEs) occurred in 3.7% of hospitalized patients.^2,3 Similar studies have found equivalent or greater rates.^4,5,6 Other research has found that AE risk increases with design flaws in the health care system.^7,8,9,10Such flaws may particularly affect patient care immediately after hospital discharge, a period associated with discontinuities in providers and in location of care. Some authors suggest that such “gaps” are important causes of error.¹¹ It is also a time when patients frequently experience extensive changes in health¹² and therapy.¹³ Finally, communication between hospital and community physicians can be inadequate.¹⁴ For these reasons, AEs may be common after discharge. A recent study, by a group that included 1 of us, found that 19% of medical patients discharged from a single teaching hospital in the United States experienced an AE within a month.¹⁵ One-third of these AEs were preventable because they were due to an error. Another third were judged “ameliorable” because their severity could have been reduced with better monitoring or earlier response to the problem.¹⁵That study was important, but it had limitations. It was carried out in a single, very specialized institution, it relied on data available in an electronic medical record, and it had a high rate of loss to follow-up. To address these concerns, we carried out a new study to determine the risk, severity and type of AEs after discharge from 2 campuses of a Canadian teaching hospital.     

Water Relations and Hydraulic Architecture of a Tropical Tree (Schefflera morototoni) : Data, Models, and a Comparison with Two Temperate Species (Acer saccharum and Thuja occidentalis)

The water relations and hydraulic architecture of a tropical tree (Schefflera morototoni) and of two temperate species (Acer saccharum and Thuja occidentalis) are reported. Among the water relations parameters measured were leaf and stem water storage capacity, leaf water potential, transpiration, and vulnerability of stems to cavitation and loss of hydraulic conductivity by embolisms. Among the hydraulic architecture parameters measured were hydraulic conductivity per unit pressure gradient, specific conductivity, leaf-specific conductivity, and Huber value. In terms of vulnerability of stems to cavitation, stem and leaf capacitances, and leaf-specific conductivity, all three species followed the same sequence: Schefflera > Acer > Thuja. It is argued here that the high stem capacitance and high leaf-specific conductivity of Schefflera are necessary to compensate for its high vulnerability to cavitation. Extractable water storage per unit leaf area in Schefflera stems is >100 times that of Acer and may permit the species to survive unusually long, dry seasons in Panama. Although Schefflera frequently grows >20 meters, the biggest resistance to water flow in the shoots resides in the leaves.     

Using nonlinear least squares to assess relative expression and its uncertainty in real-time qPCR studies

Relative expression ratios are commonly estimated in real-time qPCR studies by comparing the quantification cycle for the target gene with that for a reference gene in the treatment samples, normalized to the same quantities determined for a control sample. For the “standard curve” design, where data are obtained for all four of these at several dilutions, nonlinear least squares can be used to assess the amplification efficiencies (AE) and the adjusted ΔΔC_q and its uncertainty, with automatic inclusion of the effect of uncertainty in the AEs. An algorithm is illustrated for the KaleidaGraph program.