bluuebunny/crossref_metadata_2025 huggingface dataset:
Lubrication of Microelectromechanical Devices Using Liquids of Different Viscosities
Authors: Ku I. S. Y. , Reddyhoff T. , Wayte R. , Choo J. H. , Holmes A. S. , Spikes H. A.
Published: March 2012

Lubrication of contacting and sliding surfaces in MEMS (microelectromechanical systems) is particularly challenging because of the predominance of surface forces at the microscale. The current paper explores the possibility of using liquid lubrication in this application. Measurements of friction and lubricant film thickness have been made for liquid lubricants of different viscosities, including low viscosity silicone oil, hexadecane, squalane, and water. Testing was carried out using a newly developed MEMS tribometer in which a rotating silicon disk is loaded against a stationary silicon disk. Two different test setups were used: one where both disks are flat, and the other where the stationary disk is structured as in a thrust pad bearing. In all tests the disks were fully submerged in the lubricant. With the flat-on-patterned disk combination, the variation of friction with rotation speed was found to follow classical Stribeck curves for all the lubricants tested. The friction at high speeds also decreased with increasing normal load, in accordance with hydrodynamic lubrication theory. For the least viscous lubricants, it was found that the hydrodynamic friction coefficients remained relatively low even at higher speeds. In particular, for water the friction coefficient for water was around 0.1 at 10,000 rpm. However, boundary friction was found to be unacceptably high at low speeds where there was insufficient lubricant entrainment. The experimental results have been compared with a finite difference solution of Reynolds equation and reasonable agreement is seen between theory and experiment. The results indicate that liquid lubrication is potentially an effective means of lubricating MEMS components with high levels of sliding.
Effect of Cl2- and HBr-based inductively coupled plasma etching on InP surface composition analyzed using in situ x-ray photoelectron spectroscopy
Authors: Bouchoule S. , Vallier L. , Patriarche G. , Chevolleau T. , Cardinaud C.
Published: March 2012

A Cl2-HBr-O2/Ar inductively coupled plasma (ICP) etching process has been adapted for the processing of InP-based heterostructures in a 300-mm diameter CMOS etching tool. Smooth and anisotropic InP etching is obtained at moderate etch rate (∼600 nm/min). Ex situ x-ray energy dispersive analysis of the etched sidewalls shows that the etching anisotropy is obtained through a SiOx passivation mechanism. The stoichiometry of the etched surface is analyzed in situ using angle-resolved x-ray photoelectron spectroscopy. It is observed that Cl2-based ICP etching results in a significantly P-rich surface. The phosphorous layer identified on the top surface is estimated to be ∼1–1.3-nm thick. On the other hand InP etching in HBr/Ar plasma results in a more stoichiometric surface. In contrast to the etched sidewalls, the etched surface is free from oxides with negligible traces of silicon. Exposure to ambient air of the samples submitted to Cl2-based chemistry results in the complete oxidation of the P-rich top layer. It is concluded that a post-etch treatment or a pure HBr plasma step may be necessary after Cl2-based ICP etching for the recovery of the InP material.
Elastic Domains Regulate Growth and Organogenesis in the Plant Shoot Apical Meristem
Authors: Kierzkowski Daniel , Nakayama Naomi , Routier-Kierzkowska Anne-Lise , Weber Alain , Bayer Emmanuelle , Schorderet Martine , Reinhardt Didier , Kuhlemeier Cris , Smith Richard S.
Published: March 2012

Shape-Shifting Signals

Although orthogonal signaling systems seem to direct various developmental processes, few tissues remain in the same shape as they are at initiation to that of the final form.
Arabidopsis
leaves are free of the cell migrations that complicate animal development, and thus allowed

Kuchen
et al.

(p.
1092
) to track and model the trajectory of leaf growth under a variety of perturbations. Varying the values of parameters in their model produced outputs of different leaf shapes ranging from obcordate, ovate, and oval to elliptic, and offered predictions for genes that regulate the developmental process. The meristem at the growing tip of plants is home to stem cells and is the source of newly differentiating shoots and leaves. New leaves make their first appearance as bulges at the side of the dome-shaped meristem. Although these developmental events are under hormonal control, they also seem to be constrained by the physical properties of the meristem.

Kierzkowski
et al.

(p.
1096
) tested physical effects acting on the shoot apical meristem of growing tomato shoots that alter turgor pressure. Again, mathematical modeling combined with observations of plant tissue helped to define the different zones in the meristem that respond to diverse mechanical stimuli.
Identification of the Social and Cognitive Processes Underlying Human Cumulative Culture
Authors: Dean L. G. , Kendal R. L. , Schapiro S. J. , Thierry B. , Laland K. N.
Published: March 2012

Acquire and Share

Few would argue with the stance that human social cognition supports an unequaled capacity to acquire knowledge and to share it with others.

Dean
et al.

(p.
1114
; see the Perspective by

Kurzban and Barrett

) compared the extent to which these social and cognitive psychological processes can be elicited in children, capuchins, and chimpanzees through the use of a three-level puzzlebox task. Incentivized by improving rewards, 3- to 4-year-old children progressed from the first to the third level by imitating observed actions, taught other members of their social group how to solve the problem, and shared the rewards obtained. By contrast, neither the capuchins nor chimpanzees, very few of which ever reached the third level, exhibited these charactertistics.
Catalysis and Sulfa Drug Resistance in Dihydropteroate Synthase
Authors: Yun Mi-Kyung , Wu Yinan , Li Zhenmei , Zhao Ying , Waddell M. Brett , Ferreira Antonio M. , Lee Richard E. , Bashford Donald , White Stephen W.
Published: March 2012

Sulfa's Crystal View

The sulfonamide antibiotics (sulfa drugs) have been used to treat infections for over 70 years; however, emerging resistance has eroded their clinical utility. Sulfa drugs target dihydropteroate synthase, a key enzyme in the bacterial folate pathway. By performing the reaction in the crystalline form of the enzyme,

Yun
et al.

(p.
1110
) have characterized the key structural intermediates. In combining structural data with theoretical and mutagenesis studies, they propose a detailed mechanism for dihydropteroate synthase catalysis. By resolving this structure with a sulfa drug bound to the enzyme, they showed how inhibition occurred and indicated how resistance could emerge.
Response to Comment on “Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa”
Authors: Atkinson Quentin D.
Published: March 2012

Jaeger
et al.
use statistical simulations to show that the serial founder effect analysis I reported has an inflated type 1 error rate. Crucially, however, their simulations also reveal that the strength of the observed relationship between phonemic diversity and distance from Africa is unlikely to be due to chance, even accounting for multiple comparisons and geographic clustering of phonemic diversity.
No Straight Path: Roaming in Both Ground- and Excited-State Photolytic Channels of NO
3
→ NO + O
2
Authors: Grubb Michael P. , Warter Michelle L. , Xiao Hongyan , Maeda Satoshi , Morokuma Keiji , North Simon W.
Published: March 2012

Exclusive Roaming

How do polyatomic molecules fall apart? The basic model, supported by centuries of chemical theory and experiment, invokes a series of internal rearrangements that lead to a fleeting high-energy transition-state geometry from which lower-energy products emerge. Over the past decade, several molecules have been shown to manifest a competing dissociation mechanism such that alongside trajectories that pass through the transition state, there are energetically accessible pathways that roam around it.

Grubb
et al.

(p.
1075
; see the Perspective by

Jordan and Kable

) showed that the light-induced reaction of NO
3
to form NO and O
2
proceeded exclusively by roaming. Although there are distinct pathways to the products in two different electronic states, neither one passes through a conventional transition state.
Probing the Mantle Past
Authors: Bennett Vickie C.
Published: March 2012

Precision isotope analysis can reveal details of the dynamic processes involved in the formation of Earth's mantle.
Overhaul of U.S. Child Health Study Concerns Investigators
Authors: Kaiser Jocelyn
Published: March 2012

A controversial health study of 100,000 U.S. children hit another rough patch last month when the National Institutes of Health announced that it may modify its sampling plan in 2013 to save money.
Is the World Tottering on the Precipice of Peak Gold?
Authors: Kerr Richard A.
Published: March 2012

Seventeen-hundred-dollar-an-ounce gold is driving a mining frenzy, but analysts are concerned that miners can't extract gold any faster than they have the past decade.
LIFE SCIENCE TECHNOLOGIES: Animal-Free Toxicology: Sometimes, in Vitro is Better
Authors: Perkel Jeffrey M.
Published: March 2012

The next time you use shampoo, air freshener, or moisturizing cream, consider this: How do you know it's safe? In all likelihood, whatever toxicologic screening its component ingredients were subjected to involved laboratory animals, the method of choice for decades and the industry's reigning "gold standard." Yet as Bob Dylan once put it, the times, they are a-changing. Animal-based testing is expensive and time-consuming, morally and ethically troubling, and most significantly, often a poor predictor of human toxicity. Animals aren't going anywhere just yet. But their numbers are dropping. Driven both by legislative mandate and scientific need, a new suite of in vitro and cell culture-based animal-free methods are gaining a foothold in toxicology labs.
In Vitro
Antimicrobial Susceptibility to Isepamicin of 6,296 Enterobacteriaceae Clinical Isolates Collected at a Tertiary Care University Hospital in Greece
Authors: Maraki Sofia , Samonis George , Karageorgopoulos Drosos E. , Mavros Michael N. , Kofteridis Diamantis , Falagas Matthew E.
Published: March 2012

The reevaluation of “forgotten” antibiotics can identify new therapeutic options against extensively drug-resistant Gram-negative pathogens. We sought to investigate isepamicin in this regard. We retrospectively evaluated the antimicrobial susceptibility to isepamicin of
Enterobacteriaceae
sp. isolates from unique patients, collected at the microbiological laboratory of the University Hospital of Heraklion, Crete, Greece, from 2004 to 2009. Susceptibility testing was done with the automated Vitek 2 system. The breakpoints for susceptibility to isepamicin, tigecycline, and other antibiotics were those proposed by the Comité de l'Antibiogramme de la Société Française de Microbiologie (CA-SFM), the FDA, and the CLSI, respectively. A total of 6,296 isolates were studied, including primarily 3,401 (54.0%)
Escherichia coli
, 1,040 (16.5%)
Klebsiella pneumoniae
, 590 (9.4%)
Proteus mirabilis
, and 460 (7.3%)
Enterobacter
sp. isolates. Excluding the species with intrinsic resistance to each antibiotic, antimicrobial susceptibility was highest for colistin (5,275/5,441 isolates [96.9%]) and isepamicin (6,103/6,296 [96.9%]), followed by meropenem (5,890/6,296 [93.6%]), imipenem (5,874/6,296 [93.3%]), and amikacin (5,492/6,296 [87.2%]). The antimicrobial susceptibility of the 1,040
K. pneumoniae
isolates was highest for isepamicin (95.3%), followed by colistin (89.3%) and meropenem (63.0%). Regarding resistant
K. pneumoniae
isolates, susceptibility to isepamicin was observed for 91.1% of the 392, 87.7% of the 375, and 85.6% of the 111 isolates that were nonsusceptible to the carbapenems, all other aminoglycosides, and colistin, respectively. Isepamicin exhibited high
in vitro
activity against almost all of the
Enterobacteriaceae
species. It could particularly serve as a last-resort therapeutic option for carbapenem-resistant
K. pneumoniae
in our region, where it is endemic, as it does not show considerable cross-resistance with other aminoglycosides.
Development of a Robust Cytopathic Effect-Based High-Throughput Screening Assay To Identify Novel Inhibitors of Dengue Virus
Authors: McCormick Kevin D. , Liu Shufeng , Jacobs Jana L. , Marques Ernesto T. A. , Sluis-Cremer Nicolas , Wang Tianyi
Published: March 2012

We have developed a robust cytopathic effect-based high-throughput screening assay to identify inhibitors of dengue virus (DENV) infection. Screening of a small natural product library yielded 11 hits. Four of these were found to be potent inhibitors of DENV, although serotype differences were noted. Taken together, these data suggest that screening of larger and more complex molecule libraries may result in the identification of more potent and specific DENV inhibitors.
Tetanus Toxin and Botulinum Toxin A Utilize Unique Mechanisms To Enter Neurons of the Central Nervous System
Authors: Blum Faith C. , Chen Chen , Kroken Abby R. , Barbieri Joseph T.
Published: March 2012

Botulinum neurotoxins (BoNTs) and tetanus neurotoxin (TeNT) are the most toxic proteins for humans. While BoNTs cause flaccid paralysis, TeNT causes spastic paralysis. Characterized BoNT serotypes enter neurons upon binding dual receptors, a ganglioside and a neuron-specific protein, either synaptic vesicle protein 2 (SV2) or synaptotagmin, while TeNT enters upon binding gangliosides as dual receptors. Recently, TeNT was reported to enter central nervous system (CNS) neurons upon synaptic vesicle cycling that was mediated by the direct binding to SV2, implying that TeNT and BoNT utilize common mechanisms to enter CNS neurons. This prompted an assessment of TeNT entry into CNS neurons, using the prototypic BoNT serotype A as a reference for SV2-mediated entry into synaptic vesicles, analyzing the heavy-chain receptor binding domain (HCR) of each toxin. Synaptic vesicle cycling stimulated the entry of HCR/A into neurons, while HCR/T entered neurons with similar levels of efficiency in depolarized and nondepolarized neurons. ImageJ analysis identified two populations of cell-associated HCR/T in synaptic vesicle cycling neurons, a major population which segregated from HCR/A and a minor population which colocalized with HCR/A. HCR/T did not inhibit HCR/A entry into neurons in competition experiments and did not bind SV2, the protein receptor for BoNT/A. Intoxication experiments showed that TeNT efficiently cleaved VAMP2 in depolarized neurons and neurons blocked for synaptic vesicle cycling. These experiments demonstrate that TeNT enters neurons by two pathways, one independent of stimulated synaptic vesicle cycling and one by synaptic vesicles independent of SV2, showing that TeNT and BoNT/A enter neurons by unique mechanisms.
The Sum1/Ndt80 Transcriptional Switch and Commitment to Meiosis in Saccharomyces cerevisiae
Authors: Winter Edward
Published: March 2012

Cells encounter numerous signals during the development of an organism that induce division, differentiation, and apoptosis. These signals need to be present for defined intervals in order to induce stable changes in the cellular phenotype. The point after which an inducing signal is no longer needed for completion of a differentiation program can be termed the “commitment point.” Meiotic development in the yeast
Saccharomyces cerevisiae
(sporulation) provides a model system to study commitment. Similar to differentiation programs in multicellular organisms, the sporulation program in yeast is regulated by a transcriptional cascade that produces early, middle, and late sets of sporulation-specific transcripts. Although critical meiosis-specific events occur as early genes are expressed, commitment does not take place until middle genes are induced. Middle promoters are activated by the Ndt80 transcription factor, which is produced and activated shortly before most middle genes are expressed. In this article, I discuss the connection between Ndt80 and meiotic commitment. A transcriptional regulatory pathway makes
NDT80
transcription contingent on the prior expression of early genes. Once Ndt80 is produced, the recombination (pachytene) checkpoint prevents activation of the Ndt80 protein. Upon activation, Ndt80 triggers a positive autoregulatory loop that leads to the induction of genes that promote exit from prophase, the meiotic divisions, and spore formation. The pathway is controlled by multiple feed-forward loops that give switch-like properties to the commitment transition. The conservation of regulatory components of the meiotic commitment pathway and the recently reported ability of Ndt80 to increase replicative life span are discussed.
Diatom-inferred decline of macrophyte abundance in lakes of southern Quebec, Canada
Authors: Vermaire Jesse C. , Prairie Yves T. , Gregory-Eaves Irene
Published: March 2012

Submerged macrophytes play a central role in lake ecosystem functioning; however, their long-term dynamics are poorly understood. We have used the paleolimnological top–bottom approach to reconstruct changes in whole-lake macrophyte biomass between predisturbance and present-day conditions in 37 southern Quebec lakes. Estimates of whole-lake macrophyte biomass were produced using a diatom-based multivariate regression tree model (MRT) and modern analogue approach. Both approaches indicated an overall pattern of declining macrophyte abundance in the region. Based on MRT analysis, 80% of study lakes were classified as historically being in the macrophyte-dominated state, but now only 43% of the lakes are currently in this state. The lakes that shifted MRT group were found to have significantly (p = 0.03) greater building densities in their catchments compared with lakes that did not shift state. These results suggest that human impacts, primarily nutrient inputs and water level fluctuations, have played a role in reducing macrophyte abundance in southern Quebec lakes. Because submerged macrophyte beds help stabilize lake ecosystems and act as a phosphorus sink, a reduction in whole-lake macrophyte biomass could make lake ecosystems more susceptible to eutrophication.
The expected time to attain chemical equilibrium from a thermodynamic probabilistic analysis
Authors: Pastore Christopher , Garfinkle Moishe
Published: March 2012

Employing a stochastic model, both Planck and Fokker proposed almost a century ago that stoichiometric chemical reactions proceed by a chain mechanism involving discrete reaction steps. To determine whether such a chain mechanism was in fact a valid mechanism for chemical reactions was the subject of a recent study (Garfinkle, M. 2002. J. Phys. Chem. 106A: 490). Using a thermodynamic–probabilistic algorithm the stochastic reaction paths were found to be in excellent agreement with the observed reaction paths plotted from experimental data. This study was then extended to test the conclusions of Ehrenfest and Prigogine that a chain mechanism dictates that the number of discrete reaction steps required for a chemical reaction to attain equilibrium must be finite. The stochastic and empirical reaction paths were compared using experimental data for first-, second-, and third-order reactions as well as fractional order reactions. The empirical verification was excellent.
A liquid chromatography – mass spectrometry method to measure 13C-isotope enrichment for DNA stable-isotope probing
Authors: Auclair Julie , Lépine François , Villemur Richard
Published: March 2012

DNA stable-isotope probing (DNA-SIP) is a cultivation-independent technique that makes it possible to associate metabolic function and taxonomic identity in a wide range of terrestrial and aquatic environments. In DNA-SIP, DNA is labeled via the assimilation of a labeled growth substrate that is subsequently used to identify microorganisms involved in assimilation of the substrate. However, the labeling time has to be sufficient to obtain labeled DNA but not so long such that cross-feeding of 13C-labeled metabolites from the primary consumers to nontarget species can occur. Confirmation that the DNA is isotopically labeled in DNA-SIP assays can be achieved using an isotope ratio mass spectrometer. In this study, we describe the development of a method using liquid chromatography (HPLC) coupled to a quadrupole mass spectrometer (QMS) to measure the 13C enrichment of thymine incorporated into DNA in Escherichia coli cultures fed with [13C]acetate. The method involved the hydrolysis of DNA extracted from the cultures that released the nucleotides, followed by the separation of the thymine by HPLC on a reverse-phase C8 column in isocratic elution mode and the detection and quantification of 13C-labeled thymine by QMS. To mimic a DNA-SIP assay, a DNA mixture was made using 13C-labeled E. coli DNA with DNA extracted from five bacterial species. The HPLC–MS method was able to measure the correct proportion of 13C-DNA in the mix. This method can then be used as an alternative to the use of isotope ratio mass spectrometry in DNA-SIP assays.
Cangene Gold Medal Award Lecture — Genomic analysis and modification ofBurkholderia cepaciacomplex bacteriophages1This article is based on a presentation by Dr. Karlene Lynch at the 61st Annual Meeting of the Canadian Society of Microbiologists in St. John’s, Newfoundland and Labrador, on 21 June 2011. Dr. Lynch was the recipient of the 2011 Cangene Gold Medal as the Canadian Graduate Student Microbiologist of the Year, an annual award sponsored by Cangene Corporation intended to recognize excellence in graduate research.
Authors: Lynch Karlene H. , Dennis Jonathan J.
Published: March 2012

The Burkholderia cepacia complex (Bcc) is a group of 17 Gram-negative predominantly environmental bacterial species that cause potentially fatal opportunistic infections in cystic fibrosis (CF) patients. Although its prevalence in these individuals is lower than that of Staphylococcus aureus and Pseudomonas aeruginosa , the Bcc remains a serious problem in the CF community because of the pathogenicity, transmissibility, and inherent antibiotic resistance of these organisms. An alternative treatment for Bcc infections that is currently being developed is phage therapy, the clinical use of viruses that infect bacteria. To assess the suitability of individual phage isolates for therapeutic use, the complete genome sequences of a panel of Bcc‐specific phages were determined and analyzed. These sequences encode a broad range of proteins with a gradient of relatedness to phage and bacterial gene products from Burkholderia and other genera. The majority of these phages were found not to encode virulence factors, and despite their predominantly temperate nature, a proof-of-principle experiment has shown that they may be modified to a lytic form. Both the genomic characterization and subsequent engineering of Bcc‐specific phages are fundamental to the development of an effective phage therapy strategy for these bacteria.
Heterologous expression of bacterial nitric oxide synthase gene: a potential biological method to control biofilm development in the environment
Authors: Liu Pulin , Huang Qiaoyun , Chen Wenli
Published: March 2012

The nitric oxide synthase gene from Bacillus subtilis was heterologously expressed in Pseudomonas putida using a broad-host expression vector. Both the performance of the nitric oxide-specific fluorescent probe and the quantitative assessment of the nitric oxide end products demonstrated the generation of nitric oxide. The endogenous nitric oxide increased the motility of P. putida and decreased the capacity of P. putida and other multispecies bacteria to develop biofilms. On the practical side, endogenous nitric oxide offers an advantage in generating continuous, controllable levels of nitric oxide, which suggests a new method to use nitric oxide in the control of biofilms.
CSM Murray Award Lecture — Functional studies of the Lyme disease spirochete — from molecules to mice1This article is based on a presentation by Dr. George Chaconas at the 61st Annual Meeting of the Canadian Society of Microbiologists in St. John’s, Newfoundland, on 20 June 2011. Dr. Chaconas was the recipient of the CSM Murray Award for Career Achievement.
Authors: Chaconas George
Published: March 2012

Lyme borreliosis, also known as Lyme disease, is now the most common vector transmitted disease in the northern hemisphere. It is caused by the spirochete Borrelia burgdorferi and related species. In addition to their clinical importance, these organisms are fascinating to study because of the wide variety of unusual features they possess. Ongoing work in the laboratory in several areas will be described. (1) The segmented genomes contain up to two dozen genetic elements, the majority of which are linear with covalently closed hairpin ends. These linear DNAs also display a very high degree of ongoing genetic rearrangement. Mechanisms for these processes will be described. (2) Persistent infection by Borrelia species requires antigenic variation through a complex DNA rearrangement process at the vlsE locus on the linear plasmid lp28-1. Novel features of this recombination process will be presented. (3) Evidence for a new global regulatory pathway of B. burgdorferi gene expression that is required for pathogenicity will be described. The DEAH box RNA helicase HrpA is involved in this pathway, which may be relevant in other bacteria. (4) The mechanism of B. burgdorferi to effectively disseminate throughout its host is being studied in real time by high resolution intravital imaging in live mice. Recent work will be presented.
Investigating the influence of LiDAR ground surface errors on the utility of derived forest inventories
Authors: Tinkham Wade T. , Smith Alistair M.S. , Hoffman Chad , Hudak Andrew T. , Falkowski Michael J. , Swanson Mark E. , Gessler Paul E.
Published: March 2012

Light detection and ranging, or LiDAR, effectively produces products spatially characterizing both terrain and vegetation structure; however, development and use of those products has outpaced our understanding of the errors within them. LiDAR’s ability to capture three-dimensional structure has led to interest in conducting or augmenting forest inventories with LiDAR data. Prior to applying LiDAR in operational management, it is necessary to understand the errors in LiDAR-derived estimates of forest inventory metrics (i.e., tree height). Most LiDAR-based forest inventory metrics require creation of digital elevation models (DEM), and because metrics are calculated relative to the DEM surface, errors within the DEMs propagate into delivered metrics. This study combines LiDAR DEMs and 54 ground survey plots to investigate how surface morphology and vegetation structure influence DEM errors. The study further compared two LiDAR classification algorithms and found no significant difference in their performance. Vegetation structure was found to have no influence, whereas increased variability in the vertical error was observed on slopes exceeding 30°, illustrating that these algorithms are not limited by high-biomass western coniferous forests, but that slope and sensor accuracy both play important roles. The observed vertical DEM error translated into ±1%–3% error range in derived timber volumes, highlighting the potential of LiDAR-derived inventories in forest management.
Dendrochronological analysis of baldcypress (Taxodium distichum) responses to climate and contrasting flood regimes
Authors: Keim Richard F. , Amos J. Blake
Published: March 2012

Baldcypress (Taxodium distichum (L.) Rich.) has been used extensively for dendrochronological reconstruction of climate and is a key species in globally important wetlands with complex, poorly understood relationships between hydrological and ecological processes. To better understand ecosystem responses to changing climate and hydrology and to test whether hydrological or climatological variables are most reflected in chronologies, we developed tree-ring chronologies for six stagnant or riverine swamps in the Mississippi River deltaic plain and modeled growth responses to historical hydrology (51 years of data) and climate (111 years of data). Decoupled flooding and local climate in this deltaic setting allowed for relatively independent assessments of the roles of hydrology and climate in baldcypress growth. Depth of annual flooding was positively correlated with growth that year but negatively correlated with growth in the ensuing year for both riverine and stagnant swamps. Depth of 10-year mean flooding was positively correlated with growth in riverine swamps but negatively correlated with growth in stagnant swamps. Results corroborate previous findings that long-term, stagnant flooding reduces productivity, but growth at these deltaic sites was less correlated with climatic variables than elsewhere. At least in these frequently flooded sites, baldcypress tree rings appear to be a better long term record of hydrological history than of climatic history.
Effects of forest management legacies on spruce budworm (Choristoneura fumiferana) outbreaks
Authors: Robert Louis-Etienne , Kneeshaw Daniel , Sturtevant Brian R.
Published: March 2012

The “silvicultural hypothesis” of spruce budworm ( Choristoneura fumiferana Clem.) dynamics postulates that increasing severity of spruce budworm outbreaks over the last century resulted from forest conditions created by past management activities. Yet, definitive tests of the hypothesis remain elusive. We examined spruce budworm outbreak dynamics (synchrony, periodicity, and intensity) in the 20th century using historical reconstruction from tree-ring chronologies sampled within 19 sites in a large ecoregion located on the border of Minnesota and Ontario. The study encompassed three areas affected by contrasting management legacies: a fine-grained area (Minnesota, six sites, average cut size = 17 ha), a coarse-grained area (Ontario, six sites, average cut size 10 times that of Minnesota), and a conservation zone (seven sites) with little recent harvest activity overlapping the border. Results suggest important differences in outbreak dynamics between the forest management zones that cannot be explained by differences in climate among sample sites. Budworm outbreaks within the conservation zone were more synchronous, with more trees per site affected and less frequent outbreaks than sites sampled within fine-scale managed areas. Outbreak dynamics within forests managed at coarser scales suggest a mixture of the conservation and fine-scale management zone outbreak patterns. Potential factors affecting differences in the observed outbreak patterns include forest pattern, composition, and age. Our study generally supports the silvicultural hypothesis and emphasizes that management legacy effects on spruce budworm dynamics should be observable at landscape scales, as well as at local scales.
Losses in understory diversity over three decades in an old-growth cool-temperate forest in Michigan, USA
Authors: Woods Kerry D. , Hicks David J. , Schultz Jan
Published: March 2012

Diversity in temperate forests is concentrated in the understory, but understory dynamics are poorly understood for old-growth forests. We use repeated measurements of more than eight hundred 1 m2plots over three decades to assess patterns of understory diversity in old-growth mesic and wet forests in northern Michigan, USA. We ask whether diversity changes systematically over time and whether dynamics are related to spatial scale. We find, for all habitats, significant understory diversity loss at square-metre scales but not at coarser scales. Total herbaceous cover, however, remained constant or increased in total and for nearly all frequent species, and no species were lost overall. We explore hypotheses about diversity regulation by exploring correlations with habitat, canopy composition, and properties of understory species. Nonindigenous plants are rare at the study site, earthworm invasion is not apparent, and deer browse is not intense. Diversity changes may be related to ecological guild membership. We suggest that the general loss of fine-scale diversity is driven by either changing canopy composition or competitive dynamics within the understory community. Management for diversity maintenance in temperate forests must address understory communities; if herbaceous diversity is scale dependent and unstable over decadal time frames, management approaches need to account for factors driving changes.
Identification of representative sampling heights for specific gravity and moisture content in plantation-grown loblolly pine (Pinus taeda)
Authors: Antony Finto , Schimleck Laurence R. , Daniels Richard F.
Published: March 2012

Conventionally, increment cores collected at breast height (1.4 m) have been used to measure wood properties of standing loblolly pine (Pinus taeda L.) trees. This height has been used because of the ease of sampling and cost involved in extracting the cores. In this study, the efficacy of a breast-height core to represent whole-tree specific gravity (SG) and moisture content (MC) was examined. The sampling height that best represents whole-tree SG and MC was identified using the correlation between volume-weighted whole-tree SG and MC with SG and MC measurements collected at different heights within a tree. We found a high correlation between observed whole-disk SG and MC with volume-weighted whole-tree SG and MC at most sampling heights. The strength of the correlation followed a skewed parabolic curve form for both wood properties. The strongest correlations were observed between 4.6 and 6.1 m, with marginally lower correlations at the base of the tree, and the weakest correlations were observed towards the tip of the tree. In addition, it was found that the number of stands and trees that need to be sampled to achieve a certain accuracy in overall mean whole-tree SG and MC was greater if breast height was used as a sampling height compared with the most representative sampling heights identified (4.6 m for SG and 6.1 m for MC).
Woody debris and tree regeneration dynamics following severe wildfires in Arizona ponderosa pine forests
Authors: Roccaforte John P. , Fulé Peter Z. , Chancellor W. Walker , Laughlin Daniel C.
Published: March 2012

Severe forest fires worldwide leave behind large quantities of dead woody debris and regenerating trees that can affect future ecosystem trajectories. We studied a chronosequence of severe fires in Arizona, USA, spanning 1 to 18 years after burning to investigate postfire woody debris and regeneration dynamics. Snag densities varied over time, with predominantly recent snags in recent fires and broken or fallen snags in older fires. Coarse woody debris peaked at > 60 Mg/ha in the time period 6–12 years after fire, a value higher than previously reported in postfire fuel assessments in this region. However, debris loadings on fires older than 12 years were within the range of recommended management values (11.2–44.8 Mg/ha). Overstory and regeneration were most commonly dominated by sprouting deciduous species. Ponderosa pine ( Pinus ponderosa C. Lawson var. scopulorum Engelm.) overstory and regeneration were completely lacking in 50% and 57% of the sites, respectively, indicating that many sites were likely to experience extended periods as shrublands or grasslands rather than returning rapidly to pine forest. More time is needed to see whether these patterns will remain stable, but there are substantial obstacles to pine forest recovery: competition with sprouting species and (or) grasses, lack of seed sources, and the forecast of warmer, drier climatic conditions for coming decades.
Why mountain pine beetle exacerbates a principal–agent relationship: exploring strategic policy responses to beetle attack in a mixed species forest
Authors: Bogle Tim , Cornelis van Kooten G.
Published: March 2012

The management of public forestland is often carried out by private forest companies, in which case the landowner needs to exercise care in dealing with catastrophic natural disturbance. We use the mountain pine beetle ( Dendroctonus ponderosae Hopkins, 1902) damage in British Columbia to explore how the public resource owner can protect future timber supply while salvaging damaged stands. We examine the variability and timing of beetle attack in a mixed species forest using mathematical programming to schedule harvest but employ the novel strategy of maximizing the timber portfolio at the end of the 20 year time horizon rather than net present value. Various financial and even-flow constraints insure a modicum of stability during the salvage period. We also model supply of adequate feedstock for electricity generation. Based on our study, the optimal short-run response to beetle damage is to increase harvests in stands with 70% or more lodgepole pine ( Pinus contorta var. latifolia Engelm. ex S. Watson) that would otherwise be uneconomic to harvest, similar to operational practice reported by the BC government. The government could focus on stable supply of individual forest products over the time horizon, thereby also stabilizing short-term revenues. Alternatively, it could emphasize an even-flow of total harvest to greatly enhance revenues (which also exhibit greater volatility) and rely more heavily on future harvests of damaged timber. Regardless of the strategy chosen, optimizing future timber supply potential means that a large proportion (about 25% in this study) of damaged pine is left for future harvest, although it will not be of sufficient quality to produce lumber.
Estimating damage from selective logging and implications for tropical forest management
Authors: Picard Nicolas , Gourlet-Fleury Sylvie , Forni Éric
Published: March 2012

The proportion of stems damaged by logging is a key parameter for the management of natural productive forests in the three tropical continents (Africa, Neotropics, and southeastern Asia). Based on a review of the literature and on a meta-analysis of published data, we estimated this logging damage rate for conventional logging and compared it across continents. Scaling coefficients were estimated to convert damage rate and logging intensity from one unit to another. Felled trees were smaller in the Neotropics (61 cm diameter at breast height (dbh) on average) than in Africa or Asia (92 cm dbh). A pantropical equation relating the proportion of trees damaged (α, no unit) to logging intensity (Nlog, in ha–1) was fitted: α = 1 – (1 + 0.09135Nlog)–0.70461. A significant residual continent effect was found, with lower damage in the Neotropics than in Africa or Asia for the same level of logging intensity, in agreement with the size of felled trees. The damage rate varied with the size of damaged trees and divided equally between destroyed and injured trees, with injured trees experiencing a threefold mortality rate during 5–10 years. Taking account at least of the relationship between logging damage and logging intensity would improve the accuracy of forecasts in forest management.
PSEUDO-COMPLEX GENERAL RELATIVITY: SCHWARZSCHILD, REISSNER–NORDSTRÖM AND KERR SOLUTIONS
Authors: CASPAR GUNTHER , SCHÖNENBACH THOMAS , HESS PETER OTTO , SCHÄFER MIRKO , GREINER WALTER
Published: March 2012

The pseudo-complex General Relativity (pc-GR) is further considered. A new projection method is proposed. It is shown that the pc-GR introduces automatically terms into the system which can be interpreted as dark energy. The modified pseudo-complex Schwarzschild solution is investigated. The dark energy part is treated as a liquid and possible solutions are discussed. As a consequence, the collapse of a large stellar mass into a singularity at r = 0 is avoided and no event-horizon is formed. Thus, black holes do not exist. The resulting object can be viewed as a gray star. It contains no singularity which emphasizes, again, that it is not a black hole. The corrections implied by a charged large mass object (Reissner–Nordström) and a rotating gray star (Kerr) are presented. For the latter, a special solution is presented. Finally, we will consider the orbital speed of a mass in a circular orbit and suggest a possible experimental verification.
A NEW LIE–SYSTEMS APPROACH TO SECOND-ORDER RICCATI EQUATIONS
Authors: CARIÑENA J. F. , DE LUCAS J. , SARDÓN C.
Published: March 2012

This work presents a newly renovated approach to the analysis of second-order Riccati equations from the point of view of the theory of Lie systems. We show that these equations can be mapped into Lie systems through certain Legendre transforms. This result allows us to construct new superposition rules for studying second-order Riccati equations and to reduce their integration to solving (first-order) Riccati equations.
An overview of Neoproterozoic reservoirs in Pakistan
Authors: Jamil Athar , Sheikh Riaz A.
Published: March 2012

Over time, Neoproterozoic rocks in Pakistan have intermittently attracted the interest of oil and gas exploration companies. However, despite these rocks having been penetrated by nearly 40 wells and being exposed in various parts of Pakistan, no serious efforts have yet been made to investigate their reservoir potential. Neoproterozoic rocks are exposed along the outer periphery of the Salt Range and Nagar Parker in Pakistan and in Rajasthan (India). Surface and subsurface data suggest a good correlation between outcrops in Rajasthan and wells in the Punjab Platform. However, the Neoproterozoic of the Punjab Platform seems to be somewhat different from that in Potwar, suggesting the existence of a kind of barrier or palaeo-high, separating the two basins. Proterozoic stromatolite found in a number of Himalayan sequences seems to be correlatable with similar facies encountered in other parts of the world, such as in the Abalog-1 and Yarba-1 wells in the Toudeni Basin in Mauritania and Mali, respectively. Glacial Pokhran boulder beds (representing snowball Earth) in the Hazara Basin, and reportedly in Pokran and Lawan across the border in India, also correlate with similar Neoproterozoic facies found in other parts of the world. Neoproterozoic offers a complete petroleum system. Regional data demand that the Neoproterozoic reservoir potential be re-evaluated, and a proper understanding of basinal configuration may play a vital role in future exploration success in this region.
Megascopic carbonaceous compression fossils from the Neoproterozoic Bhima Basin, Karnataka, South India
Authors: Sharma Mukund , Shukla Yogmaya
Published: March 2012

An abundant well-preserved assemblage of annulated carbonaceous compressions and impressions has been recorded from the intra-cratonic argillaceous sedimentary sequence of the Bhima basin in south India. Impressions and carbonaceous compressions recorded in the Hulkal Formation belong to annulated forms similar to the previously reported
Sinosabellidites huainanensis
,
Protoarenicola baiguashanensis
and
Pararenicola huaiyuanensis
from China. This paper discusses the diversity, systematics, affinity, biostratigraphical potential and global significance of these remains. The previously proposed worm-like body fossil affinity for these organisms, based on similarity with the Chinese assemblage, has been reinterpreted as with pre-Ediacaran epibenthic organisms. Fresh investigations of the Indian assemblage of such specimens reveal their close proximity to the algal affinity. The occurrence of global marker events, such as phosphatization, the presence of complicated annulated carbonaceous remains in the Hulkal Formation and the absence of stromatolites in the carbonate sequences of the Bhima basin, collectively indicate a Neoproterozoic, possibly pre-Sturtian age for the Bhima Group.
Structural evolution of the frontal fold–thrust belt, NW Himalayas from sequential restoration of balanced cross-sections and its hydrocarbon potential
Authors: Mishra Premanand , Mukhopadhyay Dilip K.
Published: March 2012

Two sedimentary lithotectonic zones are traditionally recognized in the northwestern Himalayan frontal fold–thrust belt in the Nahan salient: the Lesser Himalaya Zone (LHZ) and the Sub-Himalaya Zone (SHZ). The LHZ is made up of a sequence of Proterozoic to Early Cambrian rocks and the SHZ is made up of Cenozoic rock sequences, which were deposited subsequent to the India–Asia collision. Serial balanced cross-sections show that the structural geometries become increasingly complex from independent ramp anticlines near the foreland through imbricate fan/duplex to stacked-up horses towards the hinterland. Sequential restoration suggests a structural evolution in which a foreland propagating, in-sequence thrusting event was followed by out-of-sequence thrusting in an approximately break-back style. During the out-of-sequence movement, some of the ramps formed during in-sequence thrusting were repeatedly reactivated, leading to very complex structural geometries, particularly in the LHZ. In such a complexly deformed terrain, a rigorous structural modelling approach, combined with a robust geochemical and geochronological database, should be used to carry out calibrated petroleum system modelling, and thus reduce exploration risk.
The use of virtual patients in medical school curricula
Authors: Cendan Juan , Lok Benjamin
Published: March 2012

The demonstration of patient-based cases using automated technology [virtual patients (VPs)] has been available to health science educators for a number of decades. Despite the promise of VPs as an easily accessible and moldable platform, their widespread acceptance and integration into medical curricula have been slow. Here, the authors review the technological underpinnings of VPs, summarize the literature regarding the use and limitations of VPs in the healthcare curriculum, describe novel possible applications of the technology, and propose possible directions for future work.
An international basic science and clinical research summer program for medical students
Authors: Ramjiawan Bram , Pierce Grant N. , Anindo Mohammad Iffat Kabir , AlKukhun Abedalrazaq , Alshammari Abdullah , Chamsi Ahmad Talal , Abousaleh Mohannad , Alkhani Anas , Ganguly Pallab K.
Published: March 2012

An important part of training the next generation of physicians is ensuring that they are exposed to the integral role that research plays in improving medical treatment. However, medical students often do not have sufficient time to be trained to carry out any projects in biomedical and clinical research. Many medical students also fail to understand and grasp translational research as an important concept today. In addition, since medical training is often an international affair whereby a medical student/resident/fellow will likely train in many different countries during his/her early training years, it is important to provide a learning environment whereby a young medical student experiences the unique challenges and value of an international educational experience. This article describes a program that bridges the gap between the basic and clinical research concepts in a unique international educational experience. After completing two semester curricula at Alfaisal University in Riyadh, Kingdom of Saudi Arabia, six medical students undertook a summer program at St. Boniface Hospital Research Centre, in Winnipeg, MB, Canada. The program lasted for 2 mo and addressed advanced training in basic science research topics in medicine such as cell isolation, functional assessment, and molecular techniques of analysis and manipulation as well as sessions on the conduct of clinical research trials, ethics, and intellectual property management. Programs such as these are essential to provide a base from which medical students can decide if research is an attractive career choice for them during their clinical practice in subsequent years. An innovative international summer research course for medical students is necessary to cater to the needs of the medical students in the 21st century.