bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Infection Control Surveillance Data in a Long-Term–Care Facility: Use of Threshold Testing
Authors: Mylotte Joseph M.
Published: September 2009

Objective:

To describe long-term trends in nosocomial infection rates and the threshold testing method for evaluating nosocomial sur veillance data in a long-term–care facility (LTCF).

Design:

Descriptive epidemiology of prospectively collected infection control sur veillance data and application of threshold testing for detecting possible outbreaks. Threshold testing uses the binomial distribution to calculate probabilities of infection frequency at selected endemic levels (mean number of infections per month) and compares these probabilities to obser ved infection frequency.

Setting:

One hundred twenty-bed LTCF located within a public, university-affiliated hospital.

Patients And Methods:

The study period was 1987 through 1994. Yearly endemic levels of specific types of infection were calculated and threshold levels were determined using a previously published method. In this study, a probability of P=.01 was chosen to determine the threshold at a specific endemic level; if the observed number of infections in a month reached or exceeded the threshold level, the likelihood that this occurred by chance alone was 1% or less.

Interventions:

None.

Results:

The overall mean nosocomial infection rate ranged from three to five episodes per 1,000 resident care days per year; mean yearly rates from 1990 onward were higher and more stable than those from 1987 to 1989. The most common infections identified were lower respiratory tract, skin and soft tissue, urinary tract, and conjunctivitis. For each of these infections, threshold levels were calculated periodically, using only the monthly frequency of infection. Despite variations in the yearly mean endemic level of various infections, threshold levels were stable except for skin and soft-tissue infection.

Conclusions:

Threshold testing for analysis of infection control sur veillance data in the LTCF setting is straightfor ward and does not require knowledge of statistics, special computer software, or calculation of rates; given the stable population in the typical LTCF, threshold testing can be based on variations in the monthly count of infections and provides an objective evaluation of surveillance data and a method to identify when outbreaks may be occurring.
Antimicrobial Resistance in Long-Term–Care Facilities
Authors: Strausbaugh Larry J. , Crossley Kent B. , Nurse Brenda A. , Thrupp Lauri D. ,   SHEA Long-Term–Care Committee
Published: September 2009

During the last quarter century, numerous reports have indicated that antimicrobial resistance commonly is encountered in long-term–care facilities (LTCFs). Gramnegative uropathogens resistant to penicillin, cephalosporin, aminoglycoside, or fluoroquinolone antibiotics and methicillin-resistant Staphylococcus aureus have received the greatest attention, but other reports have described the occurrence of multiply-resistant strains of Haemophilus influenzae and vancomycin-resistant enterococci (VRE) in this setting. Antimicrobial-resistant bacteria may enter LTCFs with colonized patients transferred from the hospital, or they may arise in the facility as a result of mutation or gene transfer. Once present, resistant strains tend to persist and become endemic. Rapid dissemination also has been documented in some facilities. Person-to-person transmission via the hands of healthcare workers appears to be the most important means of spread. The LTCF patients most commonly affected are those with serious underlying disease, poor functional status, wounds such as pressure sores, invasive devices such as urinary catheters, and prior antimicrobial therapy. The presence of antimicrobial-resistant pathogens in LTCFs has serious consequences not only for residents but also for LTCFs and hospitals. Experience with control strategies for antimicrobial-resistant pathogens in LTCFs is limited; however, strategies used in hospitals often are inapplicable. Six recommendations for controlling antimicrobial resistance in LTCFs are offered, and four priorities for future research are identified.
Knowledge of the Transmission of Tuberculosis and Infection Control Measures for Tuberculosis Among Healthcare Workers
Authors: Lai Kwan Kew , Fontecchio Sally A. , Kelley Anita L. , Melvin Zita S.
Published: September 2009

Two hundred seventy-five of 325 (85%) healthcare workers (HCWs) completed a questionnaire testing their knowledge of transmission of tuberculosis (TB) and infection control measures for TB. Of the 75 HCWs with no patient contact, 49 (65%) felt that masks should be worn, and 40 (53%) would use gowns. In contrast, 175 (88%) of 200 HCWs having contact with patients thought masks should be worn, and 70 (35%) would use gowns (P=.0001 and .0085, respectively). Only 87% of HCWs with patient contact felt that respiratory precautions should be instituted for TB patients. The results of our sur vey showed that HCWs should be reeducated about TB.
Assessing Blunt Cannulae as Replacements for Hypodermic Needles During Intravenous Therapy Safety and Utility
Authors: Kempen Paul Martin
Published: September 2009

Objective:

Recently, blunt 18-gauge (ga) metal cannulae have become nationally commercially available as safety products. The ability of these blunt cannulae to prevent needlestick injury and to enable direct access of all standard latex ports and vial membranes, thus eliminating hypodermic needles entirely from the intravenous (IV) drug administration process, is assessed.

Design and Setting:

In the laboratory setting, the needlestick injury potential of small-bore blunt cannulae versus hypodermic needles was studied using blinded and randomized methods. Insertion force requirements were studied for cannulae and needles. Metal 18-ga blunt cannulae were inserted into four brands of standard Y-ports and vial stoppers to assess postpuncture integrity and force requirements.

Results:

Needlestick injury did not occur using small-bore blunt cannulae (P<.001; n=51). Metal 18-ga cannulae passed into prepierced standard Y-ports as easily as hypodermic needles and without loss of Y-port integrity. Insertion of metal 18-ga cannulae without prior port puncture was possible, but was associated with substantial coring and loss of integrity of the port seal, except for IVAC brand ports (P<.03).

Conclusions:

Metal 18-ga cannulae can be inserted through virtually all intact standard rubber vial membranes or standard Y-ports to allow safe IV access. A single prepuncture of any standard latex membrane allows economical blunt metal cannula access equally efficiently as with expensive pre-slit membranes and without loss of membrane integrity.
The Effectiveness of a Needleless Intravenous Connection System An Assessment by Injury Rate and User Satisfaction
Authors: Lawrence Louann W. , Delclos George L. , Felknor Sarah A. , Johnson Philip C. , Frankowski Ralph F. , Cooper Sharon P. , Davidson Anthony
Published: September 2009

Objective:

To assess the impact of a needleless intravenous (IV) connection system on the rate of reported intravenous-connection–related (IVCR) percutaneous injuries, and to assess user satisfaction, frequency of use, and barriers to use.

Design:

A pre-post inter vention design, with injury incidence rates being compared 3 years before and 1 year after hospitalwide device implementation; and a cross-sectional descriptive user satisfaction survey.

Setting:

Two tertiar y-care teaching hospitals, one general and one pediatric, located in a large metropolitan medical center.

Outcome Variable:

All IVCR percutaneous injuries reported to the employee health ser vices at both hospitals during the years from 1989 to 1991 and 1993.

Study Population:

Survey participants were selected randomly from licensed nursing employees at both hospitals.

Intervention:

IV connection system consisting of blunt plastic cannulas and compressed latex injection sites.

Results:

After device implementation, the IVCR injury rate was reduced 62.4% (rate ratio [RR], 0.38; 95% confidence inter val [CI95], 0.27-0.53) at the general hospital and 70.2% (RR, 0.30; CI95, 0.17-0.53) at the pediatric hospital. After adjusting for the reduction in injury rate due to factors other than device implementation, the IVCR injury rate was reduced 54.5% (adjusted RR, 0.46; CI95, 0.32-0.65) at the general hospital and 57.2% (adjusted RR, 0.43; CI95, 0.24-0.78) at the pediatric hospital. Approximately 94% of survey respondents (n=478, response rate=51%) were satisfied with the device and recommended continued use. However, needles still were being used for activities that could have been performed with the needleless system because of compatibility, accessibility, and other technical problems related to the device.

Conclusions:

The device was effective in reducing the rate of reported IVCR percutaneous injuries and users were satisfied with the device, but barriers to universal use were identified.
Gender Differences in Early Suspicion of Tuberculosis in Hospitalized High-Risk Patients During 4 Epidemic Years, 1987 to 1990
Authors: Cegielski J. Peter , Goetz Matthew B. , Jacobson Jeffrey M. , Cohn Susan E. , Weinstein Robert A. , DeHovitz Jack A. , Bennett Charles L.
Published: September 2009

Objectives:

To assess the degree to which, from 1987 to 1990, physicians suspected tuberculosis (TB) in the first 2 hospital days in human immunodeficiency virus (HIV)-infected patients with pulmonary disease.

Design:

Retrospective cohort study.

Setting:

96 hospitals in five US cities.

Patients:

2,174 adult patients with acquired immunodeficiency syndrome discharged with a diagnosis of Pneumocystis carinii pneumonia from 1987 to 1990. The diagnosis generally was not known on admission.

Results:

Physicians suspected TB in the first 2 hospital days in 66% of these patients in 1987, a rate that increased steadily to 74% in 1990. However, the extent to which physicians considered TB among female patients decreased from 76% to 71% over the 4 years. Controlling for confounding variables by multiple logistic regression, the odds that TB would be suspected early increased 1.8-fold among men (odds ratio [OR], 1.8; 95% confidence interval [CI95], 1.4-2.4), but not in women (OR, 0.6; CI95, 0.2-1.9). Among the five cities, the odds of early suspicion of TB increased most in New York City (OR, 3.9; CI95, 2.0-7.9).

Conclusions:

Physicians considered TB in a timely manner in an increasing majority of male, but not female, high-risk patients during the first years of TB resurgence in the United States. Physicians must be aware of the changing epidemiology of HIV and TB, as well as their practice patterns, to prevent nosocomial transmission of this disease
Secular Trends in the Epidemiology of Nosocomial Fungal Infections at a Teaching Hospital in Taiwan, 1981 to 1993
Authors: Nettleman Mary D. , Chen Yee-Chun , Chang Shan-Chwen , Sun Chun-Chuan , Yang Li-Se , Hsieh Wei-Chuan , Luh Kwen-Tay
Published: September 2009

Objective:

To describe the incidence and patterns of nosocomial fungal infection in a large teaching hospital in Taiwan.

Design:

Prospective, hospitalwide nosocomial surveillance data from 1981 through 1993 were analyzed to show the secular trend in nosocomial fungal infection rates and to identify the most common pathogens and sites of infection (other than skin) in this hospital.

Setting and Patients:

The National Taiwan University Hospital is a medical school-affiliated hospital in the city of Taipei, Taiwan, with a 1,200-bed capacity before 1991 and 1,500 beds since 1992. It provides both primary and tertiary medical care.

Results:

The overall nosocomial fungal infection rate rose from 0.9 infections per 1,000 discharges in 1981 to 6.6 per 1,000 discharges in 1993, with the highest rate at the medical intensive-care unit (26.5/1,000 discharges in 1993). This increase in infection rate was found at four major anatomic sites of infection, particularly including the bloodstream (0.08-2.19/1,000 discharges) and the urinary tract (0.36-2.95/1,000 discharges). Of 256 pathogens causing nosocomial fungemia from 1981 through 1993, Candida albicans was the most commonly isolated (50.8%), followed by Candida tropicalis (17.6%), Candida parapsilosis (11.7%), and Candida glabrata (8.2%). As compared to isolates from 1981 through 1988, the proportion of C parapsilosis and C glabrata isolated between 1989 and 1993 increased more than sixfold and fourfold, respectively. The increasing importance of fungal infections was confirmed further by the increased use of amphotericin B and azoles in this hospital.

Conclusions:

Candida species and other yeasts have become a prominent cause of nosocomial infections in this hospital. These fungal pathogens accounted for a higher proportion of nosocomial bloodstream and urinary infections than any single bacterial species. Therefore, it is important to conduct a prospective epidemiological study and to establish in vitro antifungal susceptibility testing to enhance efforts to control nosocomial fungal infections and to minimize the risk of emergence of antifungal resistance.
Microbiological Hazards Related to Xenotransplantation of Porcine Organs Into Man
Authors: Borie Dominic C. , Cramer Donald V. , Phan-Thanh Luu , Vaillant Jean Christophe , Bequet Jean Louis , Makowka Leonard , Hannoun Laurent
Published: September 2009

Pigs are emerging as the most likely providers of genetically engineered organs and cells for the purpose of clinical xenotransplantation. Introduction of clinical trials has been delayed primarily by uncertainties regarding the risk of swine pathogen transmission that could harm the recipient. The concern that xenotransplantation carries the potential for a new epidemic has been highlighted by recent experiences with both bovine spongiform encephalopathy and human immunodeficiency diseases.

As clinical trials have been postponed and xenotransplantation teams are working actively to gather data for an estimation of the risk, this review provides the reader with a state-of-the-art estimation of the microbiological hazards related to xenotransplantation of porcine organs to man. Particular emphasis is put on viral and retroviral hazards. Both current diagnostic tools and those under development are described, along with breeding strategies to provide donor animals that would not put the recipient or the general population at risk
Invasive ants disrupt frugivory by endemic island birds
Authors: Davis Naomi E. , O'Dowd Dennis J. , Mac Nally Ralph , Green Peter T.
Published: September 2009

Biological invasions can alter direct and indirect interactions between species, generating far-reaching changes in ecological networks that affect key ecological functions. We used model and real fruit assays to show that the invasion and formation of high-density supercolonies by the yellow crazy ant (YCA),
Anoplolepis gracilipes
, disrupt frugivory by endemic birds on Christmas Island, Indian Ocean. The overall handling rates of model fruits by birds were 2.2–2.4-fold lower in ant-invaded than in uninvaded rainforest, and pecking rates by two bird species declined by 2.6- and 4.5-fold, respectively. YCAs directly interfered with frugivory; their experimental exclusion from fruiting displays increased fruit handling threefold to sixfold, compounding indirect effects of ant invasion on resources and habitat structure that influence bird abundances and behaviours. This invasive ant, whose high densities are sustained through mutualism with introduced scale insects, rapidly decreases fruit handling by endemic island birds and may erode a key ecological function, seed dispersal. Because most other invasive ant species form expansive, high-density supercolonies that depend in part on association with hemipteran mutualists, the effects that we report here on avian frugivore–plant associations may emerge across their introduced ranges.
Fate and removal of pharmaceuticals and illicit drugs in conventional and membrane bioreactor wastewater treatment plants and by riverbank filtration
Authors: Petrovic Mira , de Alda Maria Jose Lopez , Diaz-Cruz Silvia , Postigo Cristina , Radjenovic Jelena , Gros Meritxell , Barcelo Damià
Published: September 2009

Pharmaceutically active compounds (PhACs) and drugs of abuse (DAs) are two important groups of emerging environmental contaminants that have raised an increasing interest in the scientific community. A number of studies revealed their presence in the environment. This is mainly due to the fact that some compounds are not efficiently removed during wastewater treatment processes, being able to reach surface and groundwater and subsequently, drinking waters.

This paper reviews the data regarding the levels of pharmaceuticals and illicit drugs detected in wastewaters and gives an overview of their removal by conventional treatment technologies (applying activated sludge) as well as advanced treatments such as membrane bioreactor. The paper also gives an overview of bank filtration practices at managed aquifer recharge sites and discusses the potential of this approach to mitigate the contamination by PhACs and DAs.
Illicit drugs in the environment
Authors: Zuccato Ettore , Castiglioni Sara
Published: September 2009

This paper reviews the current state of knowledge on illicit drugs as emerging environmental contaminants. Several studies have recently reported that illicit drugs are detectable in wastewater from municipal sewage treatment plants (STPs) and surface waters. These substances are excreted in urine and faeces unchanged or as active metabolites in high percentages after consumption and continuously discharged into domestic wastewaters. Residues of illicit drugs can therefore reach STPs in substantial amounts, escaping degradation, and are then released into surface waters. Environmental concentrations are low, but risks for human health and the environment cannot be excluded. Morphine, cocaine, methamphetamine and ecstasy all have potent pharmacological activities, and their presence as complex mixtures in surface waters may be toxic to aquatic organisms. Levels of residues in untreated wastewater have been used to estimate illicit drug consumption in the population. Given that current epidemiological methods are indirect and possibly biased, this evidence-based approach offers a new tool for estimating drug abuse in real time.
The formation and control of emerging disinfection by-products of health concern
Authors: Krasner Stuart W.
Published: September 2009

When drinking water treatment plants disinfect water, a wide range of disinfection by-products (DBPs) of health and regulatory concern are formed. Recent studies have identified emerging DBPs (e.g. iodinated trihalomethanes (THMs) and acids, haloacetonitriles, halonitromethanes (HNMs), haloacetaldehydes, nitrosamines) that may be more toxic than some of the regulated ones (e.g. chlorine- and bromine-containing THMs and haloacetic acids). Some of these emerging DBPs are associated with impaired drinking water supplies (e.g. impacted by treated wastewater, algae, iodide). In some cases, alternative primary or secondary disinfectants to chlorine (e.g. chloramines, chlorine dioxide, ozone, ultraviolet) that minimize the formation of some of the regulated DBPs may increase the formation of some of the emerging by-products. However, optimization of the various treatment processes and disinfection scenarios can allow plants to control to varying degrees the formation of regulated and emerging DBPs. For example, pre-disinfection with chlorine, chlorine dioxide or ozone can destroy precursors for
N
-nitrosodimethylamine, which is a chloramine by-product, whereas pre-oxidation with chlorine or ozone can oxidize iodide to iodate and minimize iodinated DBP formation during post-chloramination. Although pre-ozonation may increase the formation of trihaloacetaldehydes or selected HNMs during post-chlorination or chloramination, biofiltration may reduce the formation potential of these by-products.
Perfluorooctane sulphonate and perfluorooctanoic acid in drinking and environmental waters
Authors: Rumsby Paul C. , McLaughlin Clare L. , Hall Tom
Published: September 2009

Perfluorooctane sulphonate (PFOS) and perfluorooctanoic acid (PFOA) are chemicals that have been used for many years as surfactants in a variety of industrial and consumer products. Owing to their persistent, bioaccumulative and toxic (PBT) characteristics, PFOS has been phased out by its principal producer and the use of PFOA has been reduced. This PBT potential and a number of pollution incidents have led in recent years to an increase in studies surveying the concentrations of PFOS and PFOA in environmental waters worldwide. This paper reviews the results of these studies, as well as the monitoring that was conducted after the pollution incidents. The results of surveys suggest that PFOS and PFOA are found in environmental waters worldwide at low levels. In general, these levels are below health-based values set by international authoritative bodies for drinking water. There have been limited measurements of these chemicals in drinking water, but again these are below health-based values, except in some cases following pollution incidents. Monitoring studies suggested that where PFOS and PFOA were detected, they were at similar levels in both source and drinking water, suggesting that drinking water treatment does not remove these chemicals. However, new data show that PFOS and PFOA are effectively removed by granular activated carbon absorbers in practice. Further research is required on the newer perfluorinated chemicals that appear to be safer, but their degradation products have not as yet been fully studied.
Practical overview of analytical methods for endocrine-disrupting compounds, pharmaceuticals and personal care products in water and wastewater
Authors: Comerton Anna M. , Andrews Robert C. , Bagley David M.
Published: September 2009

The detection of organic micropollutants, such as endocrine-disrupting compounds, pharmaceuticals and personal care products, in wastewater and the aquatic environment has brought increasing concern over their potential adverse ecological and human impacts. These compounds are generally present at trace levels (ng l
−1
) and in complex water matrices, such as wastewaters and surface waters, making their analysis difficult. Currently, no standardized analytical methods are available for the analysis of organic micropollutants in environmental waters. Owing to the diversity of physico-chemical properties exhibited by the various classes of organic micropollutants, the majority of established analytical methods described in the literature focus on a specific class of compounds, with few methods applicable to multi-class compound analysis. As such, analytical challenges and limitations contribute to the lack of understanding of the effectiveness of drinking water and wastewater treatment processes to remove organic micropollutants. This paper provides a practical overview of current analytical methods that have been developed for the analysis of multiple classes of organic micropollutants from various water matrices and describes the challenges and limitations associated with the development of these methods.
Sustainable risk management of emerging contaminants in municipal wastewaters
Authors: Martin O. V. , Voulvoulis N.
Published: September 2009

The presence of emerging contaminants in municipal wastewaters, particularly endocrine-disrupting compounds such as oestrogenic substances, has been the focus of much public concern and scientific attention in recent years. Due to the scientific uncertainty still surrounding their effects, the Precautionary Principle could be invoked for the interim management of potential risks. Therefore, precautionary prevention risk-management measures could be employed to reduce human exposure to the compounds of concern. Steroid oestrogens are generally recognized as the most significant oestrogenically active substances in domestic sewage effluent. As a result, the UK Environment Agency has championed a ‘Demonstration Programme’ to investigate the potential for removal of steroid oestrogens and alkylphenol ethoxylates during sewage treatment. Ecological and human health risks are interdependent, and ecological injuries may result in increased human exposures to contaminants or other stressors. In this context of limiting exposure to potential contaminants, examining the relative contribution of various compounds and pathways should be taken into account when identifying effective risk-management measures. In addition, the explicit use of ecological objectives within the scope of the implementation of the EU Water Framework Directive poses new challenges and necessitates the development of ecosystem-based decision tools. This paper addresses some of these issues and proposes a species sensitivity distribution approach to support the decision-making process related to the need and implications of sewage treatment work upgrade as risk-management measures to the presence of oestrogenic compounds in sewage effluent.
The epidemiology and possible mechanisms of disinfection by-products in drinking water
Authors: Nieuwenhuijsen Mark J. , Grellier James , Smith Rachel , Iszatt Nina , Bennett James , Best Nicky , Toledano Mireille
Published: September 2009

This paper summarizes the epidemiological evidence for adverse health effects associated with disinfection by-products (DBPs) in drinking water and describes the potential mechanism of action.

There appears to be good epidemiological evidence for a relationship between exposure to DBPs, as measured by trihalomethanes (THMs), in drinking water and bladder cancer, but the evidence for other cancers including colorectal cancer is inconclusive and inconsistent. There appears to be some evidence for an association between exposure to DBPs, specifically THMs, and little for gestational age/intrauterine growth retardation and, to a lesser extent, pre-term delivery, but evidence for relationships with other outcomes such as low birth weight, stillbirth, congenital anomalies and semen quality is inconclusive and inconsistent. Major limitations in exposure assessment, small sample sizes and potential biases may account for the inconclusive and inconsistent results in epidemiological studies. Moreover, most studies have focused on total THMs as the exposure metric, whereas other DBPs appear to be more toxic than the THMs, albeit generally occurring at lower levels in the water.

The mechanisms through which DBPs may cause adverse health effects including cancer and adverse reproductive effects have not been well investigated. Several mechanisms have been suggested, including genotoxicity, oxidative stress, disruption of folate metabolism, disruption of the synthesis and/or secretion of placental syncytiotrophoblast-derived chorionic gonadotropin and lowering of testosterone levels, but further work is required in this area.
Organic contaminants in sewage sludge (biosolids) and their significance for agricultural recycling
Authors: Smith S. R.
Published: September 2009

Organic chemicals discharged in urban wastewater from industrial and domestic sources, or those entering through atmospheric deposition onto paved areas via surface run-off, are predominantly lipophilic in nature and therefore become concentrated in sewage sludge, with potential implications for the agricultural use of sludge as a soil improver. Biodegradation occurs to varying degrees during wastewater and sludge treatment processes. However, residues will probably still be present in the resulting sludge and can vary from trace values of several micrograms per kilogram up to approximately 1 per cent in the dry solids for certain bulk chemicals, such as linear alkylbenzene sulphonate, which is widely used as a surfactant in detergent formulations. However, the review of the scientific literature on the potential environmental and health impacts of organic contaminants (OCs) in sludge indicates that the presence of a compound in sludge, or of seemingly large amounts of certain compounds used in bulk volumes domestically and by industry, does not necessarily constitute a hazard when the material is recycled to farmland. Furthermore, the chemical quality of sludge is continually improving and concentrations of potentially harmful and persistent organic compounds have declined to background values. Thus, recycling sewage sludge on farmland is not constrained by concentrations of OCs found in contemporary sewage sludges. A number of issues, while unlikely to be significant for agricultural utilization, require further investigation and include: (i) the impacts of chlorinated paraffins on the food chain and human health, (ii) the risk assessment of the plasticizer di(2-ethylhexyl)phthalate, a bulk chemical present in large amounts in sludge, (iii) the microbiological risk assessment of antibiotic-resistant micro-organisms in sewage sludge and sludge-amended agricultural soil, and (iv) the potential significance of personal-care products (e.g. triclosan), pharmaceuticals and endocrine-disrupting compounds in sludge on soil quality and human health.
Phosphate (Pi) Starvation Effect on the Cytosolic Pi Concentration and Pi Exchanges across the Tonoplast in Plant Cells: An in Vivo 31P-Nuclear Magnetic Resonance Study Using Methylphosphonate as a Pi Analog
Authors: Pratt James , Boisson Anne-Marie , Gout Elisabeth , Bligny Richard , Douce Roland , Aubert Serge
Published: September 2009

In vivo 31P-NMR analyses showed that the phosphate (Pi) concentration in the cytosol of sycamore (Acer pseudoplatanus) and Arabidopsis (Arabidopsis thaliana) cells was much lower than the cytoplasmic Pi concentrations usually considered (60–80 μm instead of >1 mm) and that it dropped very rapidly following the onset of Pi starvation. The Pi efflux from the vacuole was insufficient to compensate for the absence of external Pi supply, suggesting that the drop of cytosolic Pi might be the first endogenous signal triggering the Pi starvation rescue metabolism. Successive short sequences of Pi supply and deprivation showed that added Pi transiently accumulated in the cytosol, then in the stroma and matrix of organelles bounded by two membranes (plastids and mitochondria, respectively), and subsequently in the vacuole. The Pi analog methylphosphonate (MeP) was used to analyze Pi exchanges across the tonoplast. MeP incorporated into cells via the Pi carrier of the plasma membrane; it accumulated massively in the cytosol and prevented Pi efflux from the vacuole. This blocking of vacuolar Pi efflux was confirmed by in vitro assays with purified vacuoles. Subsequent incorporation of Pi into the cells triggered a massive transfer of MeP from the cytosol to the vacuole. Mechanisms for Pi exchanges across the tonoplast are discussed in the light of the low cytosolic Pi level, the cell response to Pi starvation, and the Pi/MeP interactive effects.
Advances in powder diffraction pattern indexing:N-TREOR09
Authors: Altomare Angela , Campi Gaetano , Cuocci Corrado , Eriksson Lars , Giacovazzo Carmelo , Moliterni Anna , Rizzi Rosanna , Werner Per-Erik
Published: September 2009

Powder pattern indexing can still be a challenge, despite the great recent advances in theoretical approaches, computer speed and experimental devices. More plausible unit cells, belonging to different crystal systems, are frequently found by the indexing programs, and recognition of the correct one may not be trivial. The task is, however, of extreme importance: in case of failure a lot of effort and computing time may be wasted. The classical figures of merit for estimating the unit-cell reliability {i.e.M20[de Wolff (1968).J. Appl. Cryst.1, 108–113] andFN[Smith & Snyder (1979).J. Appl. Cryst.12, 60–65]} sometimes fail. For this reason, a new figure of merit has been introduced inN-TREOR09, the updated version of the indexing packageN-TREOR[Altomare, Giacovazzo, Guagliardi, Moliterni, Rizzi & Werner (2000).J. Appl. Cryst.33, 1180–1186], combining the information supplied byM20with additional parameters such as the number of unindexed lines, the degree of overlap in the pattern (the so-called number of statistically independent observations), the symmetry deriving from the automatic evaluation of the extinction group, and the agreement between the calculated and observed profiles. The use of the new parameters requires a dramatic modification of the procedures used worldwide: in the approach presented here, extinction symbol and unit-cell determination are simultaneously estimated.N-TREOR09benefits also from an improved indexing procedure in the triclinic system and has been integrated intoEXPO2009, the updated version ofEXPO2004[Altomare, Caliandro, Camalli, Cuocci, Giacovazzo, Moliterni & Rizzi (2004).J. Appl. Cryst.37, 1025–1028]. The application of the new procedure to a large set of test structures is described.
Conoscopic method for determination of main refractive indices and thickness of a uniaxial crystal cut out parallel to its optical axis
Authors: Dumitrascu Leonas , Dumitrascu Irina , Dorohoi Dana Ortansa
Published: September 2009

This paper presents a simplified data acquisition and analysis technique for use in determining the main refractive indices and thickness of a uniaxial anisotropic layer cut out parallel to the optical axis, by processing the conoscopic interference figures obtained using a polarizing microscope equipped with a CCD camera. For negative uniaxial crystals, the equations used permit the calculation of the optical sign of the studied material so it is not necessary to insert a quartz wedge into the conoscopic beam. The technique can also be applied to the study of liquid crystal layers in a planar orientation.
Re-evaluation of formulae for X-ray stress analysis in polycrystalline specimens with fibre texture: experimental confirmation
Authors: Yokoyama Ryouichi , Harada Jimpei , Akiniwa Yoshiaki
Published: September 2009

Line splitting or line broadening of an X-ray Bragg reflection owing to a three-dimensional or biaxial load on a cubic polycrystalline specimen with 〈111〉 fibre texture has been predicted by Yokoyama & Harada [J. Appl. Cryst.(2009),42, 185–191] if the specimen is in the symmetry of the Laue classm{\overline 3}m. By using a TiN film specimen and a high-precision four-circle diffractometer with a laboratory X-ray source, it is shown that the profile of the 420 reflection is substantially different with and without biaxial load and also depends on the measurement direction, while the profile of the 222 reflection does not change. These results are quantitatively in agreement with the theoretical prediction, although the theory is based on the Reuss model of elasticity.
A fast X-ray chopper for single-bunch extraction at synchrotron sources
Authors: Meents Alke , Reime Bernd , Kaiser Maik , Wang Xing-Yu , Abela Rafael , Weckert Edgar , Schulze-Briese Clemens
Published: September 2009

A new X-ray chopper system based on air-bearing technology was developed in a joint project between the Paul Scherrer Institut and DESY. The X-ray chopper wheel of 150 mm diameter has a slit width of 50 µm, which corresponds to an opening time of 230 ns at 30 000 r min−1. The wheel is equipped with either one or two slits at slightly different radii, resulting in repetition frequencies of 500 and 1000 Hz. To reduce air friction the wheel is operated in a reduced-pressure environment. The chopper is controlled by a specially developed phase lock loop controller, which is synchronized to the master bunch clock of the synchrotron. The very small and constant friction of the bearing and the high mechanical accuracy of all mechanical components in combination with the high-precision controller resulted in a very small long-term jitter of less than 3 ns. The chopper is capable of isolating X-rays generated from a single bunch of the future PETRA III storage ring at DESY operated in 40-bunch mode.
Combined sampler robot and high-performance liquid chromatography: a fully automated system for biological small-angle X-ray scattering experiments at the Synchrotron SOLEIL SWING beamline
Authors: David G. , Pérez J.
Published: September 2009

Small-angle X-ray scattering for macromolecules in solution is now widely used in structural biology to complement high-resolution structure determination obtained by X-ray crystallography or NMR. In the context of third-generation synchrotron sources, this increasing interest leads to developments in sample environments and automation. The presence of an online purification system is justified by the need for sample monodispersity. A combined system including an auto-sampler robot and online high-performance liquid chromatography (HPLC) has been developed and optimized at the SWING beamline of Synchrotron SOLEIL (Gif-sur-Yvette, France). In the sample changer mode, a few microlitres of sample can be injected between two air bubbles and circulated at a controlled speed of typically 40 µl min−1. A maximum of 14 samples per hour could be measured in this mode by remote controlling the sample injections. In the HPLC mode, an initially polydisperse sample can be separated into each of its components before immediate data acquisition. The sample cell is thermostated, and offers a visualization control and online UV–Vis absorption monitoring.
Elastic deformations in a perfect bulk Si crystal studied by high-energy X-rays
Authors: Gröschel Alexander , Grillenberger Hannes , Magerl Andreas
Published: September 2009

Long-range strain fields induced in highly perfect bulk crystals during the manufacturing process significantly affect the quality and may even lead to spontaneous fracturing. Obviously a quantitative assessment of these deformations is crucial. A possible means is to examine the diffraction of X-rays by strained crystals, as the deformations bear on the diffraction characteristics of such crystals. In this report a quantitative examination of the diffraction characteristics of a perfect silicon bulk crystal with long-range strain fields in a well defined geometry is presented. The experiments were carried out using a high-energy X-ray laboratory source. By simulating the elastic deformation of the crystal by a finite element program the strain fields of the diffracting crystal are accessed. From these, simulated data values for integrated intensities can be derived on the basis of the dynamical diffraction theory for slightly distorted crystals. The theoretical calculations show good agreement with the experimental measured values. The smallest deformation yielding a noticeable change of the integrated intensity can be associated with a bending radius of the diffracting lattice planes of 16 km.
A comparison of a microfocus X-ray source and a conventional sealed tube for crystal structure determination
Authors: Schulz Thomas , Meindl Kathrin , Leusser Dirk , Stern Daniel , Graf Jürgen , Michaelsen Carsten , Ruf Michael , Sheldrick George M. , Stalke Dietmar
Published: September 2009

Experiments are described in which a direct comparison was made between a conventional 2 kW water-cooled sealed-tube X-ray source and a 30 W air-cooled microfocus source with focusing multilayer optics, using the same goniometer, detector, radiation (Mo Kα), crystals and software. The beam characteristics of the two sources were analyzed and the quality of the resulting data sets compared. The Incoatec Microfocus Source (IµS) gave a narrow approximately Gaussian-shaped primary beam profile, whereas the Bruker AXS sealed-tube source, equipped with a graphite monochromator and a monocapillary collimator, had a broader beam with an approximate intensity plateau. Both sources were mounted on the same Bruker D8 goniometer with a SMART APEX II CCD detector and Bruker Kryoflex low-temperature device. Switching between sources simply required changing the software zero setting of the 2θ circle and could be performed in a few minutes, so it was possible to use the same crystal for both sources without changing its temperature or orientation. A representative cross section of compounds (organic, organometallic and salt) with and without heavy atoms was investigated. For each compound, two data sets, one from a small and one from a large crystal, were collected using each source. In another experiment, the data quality was compared for crystals of the same compound that had been chosen so that they had dimensions similar to the width of the beam. The data were processed and the structures refined using standard Bruker andSHELXsoftware. The experiments show that the IµS gives superior data for small crystals whereas the diffracted intensities were comparable for the large crystals. Appropriate scaling is particularly important for the IµS data.
SMEPOC– a computer program for the automatic generation of trial structural models for inorganic compounds with symmetry restriction
Authors: Deng Xiaodi , Dong Cheng
Published: September 2009

A new structure modelling algorithm that can automatically generate trial structure models based on a prior knowledge of the unit-cell content and space-group information is proposed. It can enumerate all possible equivalent position combination (EPC) models and eliminate unreasonable ones with symmetry restriction. Unlike other methods, it does not require the internal molecular connectivity or coordination polyhedron information and is mostly suitable for modelling inorganic crystals with independent atoms. Therefore, these EPC models can be used as input to global optimization procedures for inorganic crystal structure determination using powder diffraction data by the direct-space method. The efficiency of the direct-space method can be greatly improved using this EPC method because the global optimization problem in a 3N-parameter space can be divided into a set of simpler ones. A program,SMEPOC, that can generate all possible EPC models for further global optimization procedures has been developed and is now available from the authors upon request.
Maintaining Environmental Resources in the International System: A Comparison of Contractual Arrangements*
Authors: Coram Alex T.
Published: September 2009

Objectives. State A may control an environmental resource that has value for other actors in the international system. The objective of this article is to compare different contractual arrangements between State A and other agents for preservation of this resource. I concentrate on direct purchase schemes and dynamic (stream‐of‐payment) schemes.

Methods.

The problem is analyzed by constructing a model of the returns to State A from exploiting the resource; its public goods value; and transfer payments from other agents.

Results.

Among the main results are that continual transfers may be better than a one‐off buyout and, if the resource does not have a public goods value for the owner, compensation may not be effective.

Conclusions.

Generally, the analysis points out the gains to be made from paying attention to the type of contractual arrangement. Most of these results would not have been intuitively clear. I also show that rental schemes may be the least risky option.
Group cohesion in juvenile weakly electric fish Mormyrus rume proboscirostris
Authors: Khait V. , Tahiraj E. , Seemungal N. , Breakstone S. , Moller P.
Published: September 2009

The current study demonstrated that juvenile Mormyrus rume proboscirostris, an African freshwater weakly electric fish, used their active electrosense in group cohesion. Data also indicated that sight and mechano‐reception could play a synergistic role in controlling this behaviour. The developmental change from a larval monophasic electric organ discharge to the adult biphasic waveform was accompanied by a reversal of the fish's social spacing. Light was aversive to social spacing in the younger fish (aged 49 and 65 days), but facilitated aggregation in the older fish (245 days).
Swimming in four goldfish Carassius auratus morphotypes: understanding functional design and performance employing artificially selected forms
Authors: Blake R.W. , Li J. , Chan K.H.S.
Published: September 2009

Four goldfish Carassius auratus morphotypes of similar length (50 mm): common (streamlined, full complement of paired and median fins, bifurcated caudal fin), comet (‘common like’ but with a long, deeply forked caudal fin), fantail (short, deep body with twinned caudal and anal fins) and eggfish (similar to the fantail but lacking a dorsal fin) were compared. Drag, steady swimming kinematics, energetics, fast‐start performance, stability in yaw and roll and propulsive muscle ultrastructural characteristics were measured. A performance ‘pairing’ (common and comet; fantail and eggfish) was a recurrent theme for most performance variables. Fantail and eggfish drag were higher (requiring more thrust at any given velocity) than those for the more streamlined common and comet. This was reflected in kinematics; tailbeat frequency and stride length at any given velocity for the common and comet were lower and higher, respectively, than that of the fantail and eggfish. Common and comet fatigue times were not significantly different from those of their ancestor, crucian carp Carassius carassius, and higher than the fantail and eggfish. The cost of transport of the common and comet (c. 0· 6 mg O2 kg−1 m−1) was accurately predicted by the mass scaling relationship for fish, but values for the fantail and eggfish (c. 1· 3 mg O2 kg−1 m−1) were not. Rolling and yawing motions in eggfish (dorsal fin absent) during steady swimming were associated with significant energy losses. Eggfish maximum fast‐start acceleration (c. 5 m s−2) was poor due to the absence of inertial and lifting contributions to thrust from the dorsal fin and energy wasting rolling motions. Common and comet fast‐start performance (average velocity c. 0· 45 m s−1, maximum velocity c. 1· 2 m s−1, average acceleration c. 7· 5 m s−2, maximum acceleration c. 35 m s−2) was similar to that of other locomotor generalists (e.g. rainbow trout Oncorhynchus mykiss). Artificially selected fishes can contribute to the understanding of form and movement in fishes and complement studies of the role of locomotor adaptations in natural systems.
The impact of elephants, Loxodonta africana, on woody vegetation through selective debarking in Samburu and Buffalo Springs National Reserves, Kenya
Authors: Ihwagi Festus W. , Vollrath Fritz , Chira Robert M. , Douglas‐Hamilton Iain , Kironchi Geoffrey
Published: September 2009

The impact of elephants on the woody plant community through debarking was investigated in Samburu and Buffalo Springs National Reserves, Kenya. Acacia elatior Brenan, the most abundant tree species in the riverine zone, accounted for 68% (n = 1375) of woody plants. A. tortilis (Forsskal) Hayne dominated plots away from the river. Debarking incidences were significantly higher for A. elatior than for other species indicating selective utilization. The riverine zone by virtue of having more trees of the preferred species, A. elatior, had the highest debarking incidences. Presence of very few saplings along the river is attributed to both elephant trampling and herbivory by other species. An estimated 38.5% and 22.5% of the riverine A. elatior and A. tortilis trees respectively, were bound to die within the next 4–5 years because of severe debarking, ≥75% of bark circumference. Debarking was positively correlated with stem circumference; the medium‐sized trees being the worst affected by the elephants’ selective debarking behaviour. Intense debarking incidences were recorded during the dry season. Through the elephants’ selective debarking, the riverine habitat is bound to open up gradually, leading to considerable habitat change in the near future. Elephant impact on vegetation is less away from the river and increases with their densities.