bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen starvation-induced transcriptome alterations and influence of transcription regulator mutants in Mycobacterium smegmatis
Authors: Jeßberger Nadja , Lu Yinhua , Amon Johannes , Titgemeyer Fritz , Sonnewald Sophia , Reid Stephen , Burkovski Andreas
Published: November 2013

Background

As other bacteria, Mycobacterium smegmatis needs adaption mechanisms to cope with changing nitrogen sources and to survive situations of nitrogen starvation. In the study presented here, transcriptome analyses were used to characterize the response of the bacterium to nitrogen starvation and to elucidate the role of specific transcriptional regulators.

Results

In response to nitrogen deprivation, a general starvation response is induced in M. smegmatis. This includes changes in the transcription of several hundred genes encoding e.g. transport proteins, proteins involved in nitrogen metabolism and regulation, energy generation and protein turnover. The specific nitrogen-related changes at the transcriptional level depend mainly on the presence of GlnR, while the AmtR protein controls only a small number of genes.

Conclusions

M. smegmatis is able to metabolize a number of different nitrogen sources and nitrogen control in M. smegmatis is similar to control mechanisms characterized in streptomycetes, while the master regulator of nitrogen control in corynebacteria, AmtR, is plays a minor role in this regulatory network.
The plant life-cycle of the average wage of employees in U.S. manufacturing
Authors: Dinlersoz Emin , Hyatt Henry R , Nguyen Sang V
Published: November 2013

This paper explores the evolution of the average wage of employees over the life-cycle of a manufacturing plant. The average wage starts out low for a new plant and increases along with labor productivity as the plant ages. As a plant approaches exit, its average wage falls, but more slowly than it rises in the case of growing plants. Moreover, the average wage does not fall as fast as productivity does. A dynamic model of labor quality and quantity choice by plants is estimated to assess the costs of altering labor quality and quantity over the plant life-cycle.

JEL codes

J31, J21, J24, L60, L23, L11, D24
Immigration and careers of European workers: effects and the role of policies
Authors: Cattaneo Cristina , Fiorio Carlo V , Peri Giovanni
Published: November 2013

In this paper we analyze the response of career, employment and wage of native Europeans to immigration. We then ask how individual country’s policies affect these responses. We use data on 11 EU countries, over the period 1995–2001. We also use the 1991 distribution of immigrants by nationality across European labor markets to construct a version of the enclave-based instrument to proxy for the flow of immigrants, that is exogenous to local demand shocks. We find that native Europeans are more likely to upgrade to more skilled and better paid occupations, when a larger number of immigrants enter their labor market. We find no evidence of an increased likelihood of non-employment or geographical mobility. We find that more flexible labor markets in a country are a key factor to have employment upgrading in response to immigration.

JEL Codes

J61; O15
Complex conductivity tomography using low-frequency crosswell electromagnetic data
Authors: MacLennan Kris , Karaoulis Marios , Revil André
Published: November 2013

The complex conductivity of partially saturated siliciclastic sediments can now be reasonably predicted through recently developed petrophysical models like the POLARIS model. However, classical crosswell-induced polarization tomography (using a galvanometric approach) is characterized by a poor sensitivity map far from the wells, and thus other methods should be analyzed for potential improvements. The presence of low-frequency ([Formula: see text]) polarization effects in earth porous materials noticeably increases the amplitude and decreases the phase of measured electromagnetic (EM) fields. As such, the quadrature conductivity (directly associated with the low-frequency polarization effect) yields a significant contribution to the EM fields. We demonstrate that these contributions can be observed in crosswell EM data in terms of signal-to-noise ratio. With a realistic amount of noise, we can recover the distribution of the in-phase and quadrature conductivities for crosswell EM tomography. We use an integral equation approach for the forward modeling and a gradient-based approach with Tikhonov regularization for the inverse problem. We also develop a new inversion algorithm to invert time-lapse frequency domain EM data using an active-time-constrain approach. This information may be used in turn to improve our ability to monitor saturation changes in enhanced oil reservoir production, the remediation of oil spills, and the exploration and production of geothermal fields.
Transient marine electromagnetics in shallow water: A sensitivity and resolution study of the vertical electric field at short ranges
Authors: Barsukov Pavel O. , Fainberg Edward B.
Published: November 2013

We analyzed the sensitivity of transient step-off responses of shallow-water marine controlled-source electromagnetic configurations, specifically, horizontal electric dipole sources and vertical electric dipole receivers in the near field of the time domain ([Formula: see text]). The capabilities of this configuration were compared with commonly used configurations, specifically, horizontal electric dipole sources and horizontal electric dipole receivers in the frequency domain ([Formula: see text]). By examining some simplified models of local hydrocarbon reservoirs representing separate resistive bodies of limited size buried at different depths in the conductive sediments, and an example of a complex 3D geologic structure, the applications of [Formula: see text] and [Formula: see text] configurations and their limitations in terms of depth, size, and transverse resistance were evaluated.
Cost-effectiveness of cognitive–behavioural therapy as an adjunct to pharmacotherapy for treatment-resistant depression in primary care: economic evaluation of the CoBalT Trial
Authors: Hollinghurst Sandra , Carroll Fran E. , Abel Anna , Campbell John , Garland Anne , Jerrom Bill , Kessler David , Kuyken Willem , Morrison Jill , Ridgway Nicola , Thomas Laura , Turner Katrina , Williams Chris , Peters Tim J. , Lewis Glyn , Wiles Nicola
Published: November 2013

Background

Depression is expensive to treat, but providing ineffective treatment is more expensive. Such is the case for many patients who do not respond to antidepressant medication.

Aims

To assess the cost-effectiveness of cognitive–behavioural therapy (CBT) plus usual care for primary care patients with treatment-resistant depression compared with usual care alone.

Method

Economic evaluation at 12 months alongside a randomised controlled trial. Cost-effectiveness assessed using a cost-consequences framework comparing cost to the health and social care provider, patients and society, with a range of outcomes. Cost-utility analysis comparing health and social care costs with quality-adjusted life-years (QALYs).

Results

The mean cost of CBT per participant was £910. The difference in QALY gain between the groups was 0.057, equivalent to 21 days a year of good health. The incremental cost-effectiveness ratio was £14 911 (representing a 74% probability of the intervention being cost-effective at the National Institute of Health and Care Excellence threshold of £20 000 per QALY). Loss of earnings and productivity costs were substantial but there was no evidence of a difference between intervention and control groups.

Conclusions

The addition of CBT to usual care is cost-effective in patients who have not responded to antidepressants. Primary care physicians should therefore be encouraged to refer such individuals for CBT.
Association between pre- and perinatal exposures and Tourette syndrome or chronic tic disorder in the ALSPAC cohort
Authors: Mathews Carol A. , Scharf Jeremiah M. , Miller Laura L. , Macdonald-Wallis Corrie , Lawlor Debbie A. , Ben-Shlomo Yoav
Published: November 2013

Background

Tourette syndrome and chronic tic disorder are heritable but aetiologically complex. Although environment plays a role in their development, existing studies of non-genetic risk factors are inconsistent.

Aims

To examine the association between pre- and perinatal exposures and Tourette syndrome/chronic tic disorder in the Avon Longitudinal Study of Parents and Children (ALSPAC) prospective longitudinal pre-birth cohort.

Method

Relationships between exposures and Tourette syndrome/chronic tic disorder were examined in 6090 children using logistic regression.

Results

Maternal alcohol and cannabis use, inadequate maternal weight gain and parity were associated with Tourette syndrome or Tourette syndrome/chronic tic disorder. Other previously reported exposures, including birth weight and prenatal maternal smoking, were not associated with Tourette syndrome/chronic tic disorder.

Conclusions

This study supports previously reported relationships between Tourette syndrome/chronic tic disorder and prenatal alcohol exposure, and identifies additional previously unexplored potential prenatal risk factors.
The developmental trajectory of bipolar disorder
Authors: Duffy Anne , Horrocks Julie , Doucette Sarah , Keown-Stoneman Charles , McCloskey Shannon , Grof Paul
Published: November 2013

Background

Bipolar disorder is highly heritable and therefore longitudinal
observation of children of affected parents is important to mapping the
early natural history.

Aims

To model the developmental trajectory of bipolar disorder based on the
latest findings from an ongoing prospective study of the offspring of
parents with well-characterised bipolar disorder.

Method

A total of 229 offspring from families in which 1 parent had confirmed
bipolar disorder and 86 control offspring were prospectively studied for
up to 16 years. High-risk offspring were divided into subgroups based on
the parental long-term response to lithium. Offspring were clinically
assessed and DSM-IV diagnoses determined on masked consensus review using
best estimate procedure. Adjusted survival analysis and generalised
estimating equations were used to calculate differences in lifetime
psychopathology. Multistate models were used to examine the progression
through proposed clinical stages.

Results

High-risk offspring had an increased lifetime risk of a broad spectrum of
disorders including bipolar disorder (hazard ratio (HR) = 20.89;
P = 0.04), major depressive disorder (HR = 17.16;
P = 0.004), anxiety (HR = 2.20; P =
0.03), sleep (HR = 28.21; P = 0.02) and substance use
disorders (HR = 2.60; P = 0.05) compared with controls.
However, only offspring from lithium non-responsive parents developed
psychotic disorders. Childhood anxiety disorder predicted an increased
risk of major mood disorder and evidence supported a progressive
transition through clinical stages, from non-specific psychopathology to
depressive and then manic or psychotic episodes.

Conclusions

Findings underscore the importance of a developmental approach in
conjunction with an appreciation of familial risk to facilitate earlier
accurate diagnosis in symptomatic youth.
CACNA1C, schizophrenia and major depressive disorder in the Han Chinese population
Authors: He Kuanjun , An Zhiguo , Wang Qingzhong , Li Tao , Li Zhiqiang , Chen Jianhua , Li Wenjin , Wang Ti , Ji Jue , Feng Guoyin , Lin He , Yi Qizhong , Shi Yongyong
Published: November 2013

Background

Common psychiatric disorders are highly heritable, indicating that genetic factors play an important role in their aetiology. TheCACNA1Cgene, which codes for subunit alpha-1C of the Cav1.2 voltage-dependent L-type calcium channel, has been consistently found to be the shared risk gene for several kinds of mental disorder.

Aims

To investigate whetherCACNA1Cis a susceptibility gene for schizophrenia and major depressive disorder in the Han Chinese population.

Method

We carried out a case–control study of 1235 patients with schizophrenia, 1045 with major depressive disorder and 1235 healthy controls. A tag single nucleotide polymorphism (SNP) rs1006737 along with another 10 tag SNPs in theCACNA1Cgene were genotyped in all samples.

Results

We found that rs1006737 was associated with both schizophrenia (Pallele= 0.0014,Pgenotype= 0.006, odds ratio (OR) = 1.384, 95% CI 1.134–1.690) and major depressive disorder (Pallele= 0.0007,Pgenotype= 0.003, OR = 1.425, 95% CI 1.160–1.752).

Conclusions

Our findings supportCACNA1Cbeing a risk gene for both schizophrenia and major depressive disorder in the Han Chinese population.
The Targeted Inactivation of TRβ Gene in Thyroid Follicular Cells Suggests a New Mechanism of Regulation of Thyroid Hormone Production
Authors: Selmi-Ruby Samia , Bouazza Lamia , Obregon Maria-Jesus , Conscience Aude , Flamant Frédéric , Samarut Jacques , Borson-Chazot Françoise , Rousset Bernard
Published: November 2013

Thyroid epithelial cells, or thyrocytes, express functional thyroid hormone receptors but no precise role has yet been assigned to either TRα or TRβ in the thyroid gland. In this study, we analyzed the impact of inactivating the TRβ gene in the thyroid of mice. First, we generated a mouse line named Thyr-Cre, expressing the Cre recombinase under the control of the thyroglobulin gene promoter, which led to a complete recombination of floxed genes in thyrocytes. Thyr-Cre mice were then crossed with TRβ floxed mice (TRβflox/flox) to obtain a thyrocyte-selective deletion of TRβ. Thyr-TRβ−/− mice were characterized by a decrease in the size and functional activity of the thyroid gland. These alterations were associated with a decrease in plasma TSH concentration. Surprisingly, Thyr-TRβ−/− displayed elevated serum T4 and rT3 concentrations with no significant change in serum T3 levels. Their intrathyroidal free T4 and rT3 contents were also elevated, whereas the ratio of serum T4 to thyroid free T4 was decreased by comparison with wild-type littermates. Also, within the thyroid, deiodinases D1 and D2 were reduced as well as the expression levels of genes encoding monocarboxylate transporters (Mct8 and Mct10). Such a decrease in intrathyroidal deiodination of T4 and in the expression of genes encoding thyroid hormone transporters may contribute to the primary overproduction of T4 observed in Thyr-TRβ−/− mice. In conclusion, these data show that the control of thyroid hormone production involves not only TRβ-dependent mechanisms acting at the level of hypothalamus and pituitary but also TRβ-dependent mechanisms acting at the thyroid level.
TGF-β1 Regulation of Multidrug Resistance P-glycoprotein in the Developing Male Blood-Brain Barrier
Authors: Baello Stephanie , Iqbal Majid , Bloise Enrrico , Javam Mohsen , Gibb William , Matthews Stephen G.
Published: November 2013

P-glycoprotein (P-gp), an efflux transporter encoded by the abcb1 gene, protects the developing fetal brain. Levels of P-gp in endothelial cells of the blood-brain barrier (BBB) increase dramatically during the period of peak brain growth. This is coincident with increased release of TGF-β1 by astrocytes and neurons. Although TGF-β1 has been shown to modulate P-gp activity in a number of cell types, little is known about how TGF-β1 regulates brain protection. In the present study, we hypothesized that TGF-β1 increases abcb1 expression and P-gp activity in fetal and postnatal BBB in an age-dependent manner. We found TGF-β1 to potently regulate abcb1 mRNA and P-gp function. TGF-β1 increased P-gp function in brain endothelial cells (BECs) derived from fetal and postnatal male guinea pigs. These effects were more pronounced earlier in gestation when compared with BECs derived postnatally. To investigate the signaling pathways involved, BECs derived at gestational day 50 and postnatal day 14 were exposed to ALK1 and ALK5 inhibitors and agonists. Through inhibition of ALK5, we demonstrated that ALK5 is required for the TGF-β1 effects on P-gp function. Activation of ALK1, by the agonist BMP-9, produced similar results to TGF-β1 on P-gp function. However, TGF-β1 signaling through the ALK1 pathway is age-dependent as dorsomorphin, an ALK1 inhibitor, attenuated TGF-β1-mediated effects in BECs derived at postnatal day 14 but not in those derived at gestational day 50. In conclusion, TGF-β1 regulates P-gp at the fetal and neonatal BBB and both ALK5 and ALK1 pathways are implicated in the regulation of P-gp function. Aberrations in TGF-β1 levels at the developing BBB may lead to substantial changes in fetal brain exposure to P-gp substrates, triggering consequences for brain development.
Synergistic Activation of Steroidogenic Acute Regulatory Protein Expression and Steroid Biosynthesis by Retinoids: Involvement of cAMP/PKA Signaling
Authors: Manna Pulak R. , Slominski Andrzej T. , King Steven R. , Stetson Cloyce L. , Stocco Douglas M.
Published: November 2013

Both retinoic acid receptors (RARs) and retinoid X receptors (RXRs) mediate the action of retinoids that play important roles in reproductive development and function, as well as steroidogenesis. Regulation of steroid biosynthesis is principally mediated by the steroidogenic acute regulatory protein (StAR); however, the modes of action of retinoids in the regulation of steroidogenesis remain obscure. In this study we demonstrate that all-trans retinoic acid (atRA) enhances StAR expression, but not its phosphorylation (P-StAR), and progesterone production in MA-10 mouse Leydig cells. Activation of the protein kinase A (PKA) cascade, by dibutyrl-cAMP or type I/II PKA analogs, markedly increased retinoid-responsive StAR, P-StAR, and steroid levels. Targeted silencing of endogenous RARα and RXRα, with small interfering RNAs, resulted in decreases in 9-cis RA-stimulated StAR and progesterone levels. Truncation of and mutational alterations in the 5′-flanking region of the StAR gene demonstrated the importance of the −254/−1-bp region in retinoid responsiveness. An oligonucleotide probe encompassing an RXR/liver X receptor recognition motif, located within the −254/−1-bp region, specifically bound MA-10 nuclear proteins and in vitro transcribed/translated RXRα and RARα in EMSAs. Transcription of the StAR gene in response to atRA and dibutyrl-cAMP was influenced by several factors, its up-regulation being dependent on phosphorylation of cAMP response-element binding protein (CREB). Chromatin immunoprecipitation studies revealed the association of phosphorylation of CREB, CREB binding protein, RXRα, and RARα to the StAR promoter. Further studies elucidated that hormone-sensitive lipase plays an important role in atRA-mediated regulation of the steroidogenic response that involves liver X receptor signaling. These findings delineate the molecular events by which retinoids influence cAMP/PKA signaling and provide additional and novel insight into the regulation of StAR expression and steroidogenesis in mouse Leydig cells.
Beyond the zebrafish: diverse fish species for modeling human disease
Authors: Schartl Manfred
Published: November 2013

In recent years, zebrafish, and to a lesser extent medaka, have become widely used small animal models for human diseases. These organisms have convincingly demonstrated the usefulness of fish for improving our understanding of the molecular and cellular mechanisms leading to pathological conditions, and for the development of new diagnostic and therapeutic tools. Despite the usefulness of zebrafish and medaka in the investigation of a wide spectrum of traits, there is evidence to suggest that other fish species could be better suited for more targeted questions. With the emergence of new, improved sequencing technologies that enable genomic resources to be generated with increasing efficiency and speed, the potential of non-mainstream fish species as disease models can now be explored. A key feature of these fish species is that the pathological condition that they model is often related to specific evolutionary adaptations. By exploring these adaptations, new disease-causing and disease-modifier genes might be identified; thus, diverse fish species could be exploited to better understand the complexity of disease processes. In addition, non-mainstream fish models could allow us to study the impact of environmental factors, as well as genetic variation, on complex disease phenotypes. This Review will discuss the opportunities that such fish models offer for current and future biomedical research.
Factors affecting energy cost of running during an ultra-endurance race
Authors: Lazzer Stefano , Taboga Paolo , Salvadego Desy , Rejc Enrico , Simunic Bostjan , Narici Marco , Buglione Antonio , Giovanelli Nicola , Antonutto Guglielmo , Grassi Bruno , Pisot Rado , di Prampero Pietro E.
Published: November 2013

Purpose: to investigate: 1) the role of V'O2max, fraction of it (F) and metabolic cost of transport (CoT) in determining performance during an ultra-endurance competition and 2) the effects of the race on several biomechanical and morphological parameters of the lower limbs that are likely to affect CoT. Methods: Eleven runners (age: 29-54 years) participated in an ultra-endurance competition consisting of three running stages of 25, 55 and 13 km on three consecutive days. Anthropometric characteristics, body composition, morphological properties of the gastrocnemius medialis, maximal explosive power of the lower limb and V'O2max were determined before the competition. In addition, biomechanics of running and CoT was determined, before and immediately after each running stage. Results: Performance was directly proportional to V'O2max (r=0.77), and F (r=0.36) and inversely proportional to CoT (r=-0.30). Low CoT values were significantly related to high maximal power of the lower limbs (r=-0.74), vertical stiffness (r=-0.65); and low foot-print index (FPI, r=0.70), step frequency (r=0.62) and external work (r=0.60). About 50% of the increase in CoT during the stages of the competition was accounted for by changes in FPI, which represents a global evaluation of medio-lateral displacement of the foot during the whole stance phase, which in turn are associated with the myotendinous characteristics of the lower limb. Conclusions: lower CoT values were related to greater muscular power and lower FPI, suggesting that a better ankle stability is likely to achieve better performance in ultra endurance running competition.
Thyroid hormone regulates cardiac performance during cold acclimation in Zebrafish (Danio rerio)
Authors: Little Alex G. , Seebacher Frank
Published: November 2013

Limitations to oxygen transport reduce aerobic scope and thereby activity at thermal extremes. Oxygen transport in fish is facilitated to a large extent by cardiac function so that climate variability may reduce fitness by constraining the performance of the heart. In zebrafish (Danio rerio), thyroid hormone (TH) regulates skeletal muscle function and metabolism in response to thermal acclimation. Here we aimed to determine whether TH also regulates cardiac function during acclimation. We used propylthiouracil and iopanoic acid to induce hypothyroidism in zebrafish over a 3-week acclimation period to either 18 or 28°C. We found that cold-acclimated fish had higher maximum heart rates and sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) activity than warm acclimated fish. Hypothyroid treatment significantly decreased these responses in the cold acclimated fish, but it did not affect the warm-acclimated fish. TH did not influence SERCA gene transcription, nor did it increase metabolic rate, of isolated whole hearts. To verify that physiological changes following hypothyroid treatment were in fact due to the action of TH, we supplemented hypothyroid fish with 3,5-diiodothryronine (T2) or 3,5,3′-triiodothyronine (T3). Supplementation of hypothyroid fish with T2 or T3 restored heart rates and SERCA activity to control levels. We also show that in zebrafish changes in cardiac output in response to warming are primarily mediated by heart rate, rather than by stroke volume. Thus changes in heart rate are important for the overall aerobic capacity of the fish. In addition to its local effects on heart phenotype, we show that TH increases sympathetic tone on the heart at rest and during maximum exercise. Our findings reveal a new pathway through which fish can mitigate the limiting effects of temperature variability on oxygen transport to maintain aerobic scope and promote thermal tolerance.
Melatonin action in a midbrain vocal-acoustic network
Authors: Feng Ni Y. , Bass Andrew H.
Published: November 2013

Melatonin is a well-documented time-keeping hormone that can entrain an individual's physiology and behavior to the day-night cycle, though surprisingly little is known about its influence on the neural basis of social behavior, including vocalization. Male midshipman fish (Porichthys notatus) produce several call types distinguishable by duration and by daily and seasonal cycles in their production. We investigated melatonin's influence on the known nocturnal- and breeding season-dependent increase in excitability of the midshipman's vocal network (VN) that directly patterns natural calls. VN output is readily recorded from the vocal nerve as a "fictive call." Five days of constant light significantly increased stimulus threshold levels for calls electrically evoked from vocally active sites in the medial midbrain, supporting previous findings that light suppresses VN excitability, while 2-iodomelatonin (2-IMel; a melatonin analogue) implantation decreased threshold. 2-IMel also increased fictive call duration evoked from medial sites as well as lateral midbrain sites that produced several-fold longer calls irrespective of photoregime or drug treatment. When stimulus intensity was incrementally increased, 2-IMel increased duration only at lateral sites, suggesting melatonin action is stronger in the lateral midbrain. For animals receiving five days of constant darkness, known to increase VN excitability, systemic injections of either of two mammalian melatonin receptor antagonists increased threshold and decreased duration for calls evoked from medial sites. Our results demonstrate melatonin modulation of vocal network excitability and suggest that social context-dependent call types differing in duration may be determined by neuro-hormonal action within specific regions of a midbrain vocal-acoustic network.
Fast growers sprint slower: effects of food deprivation and re-feeding on sprint swimming performance in individual juvenile European sea bass
Authors: Killen Shaun S. , Marras Stefano , McKenzie David J.
Published: November 2013

While many ectothermic species can withstand prolonged fasting without mortality, food-deprivation may have sublethal effects of ecological importance, including reductions in locomotor ability. Little is known about how such changes in performance in individual animals are related either to mass loss during food-deprivation or growth rate during re-feeding. This study followed changes in the maximum sprint swimming performance of individual European sea bass Dicentrarchus labrax throughout 45 days of food-deprivation and 30 days of re-feeding. Maximum sprint speed did not show a significant decline until 45 days of food deprivation. Among individuals, the reduction in sprinting speed at this time was not related to mass loss. After 30 days of re-feeding, mean sprinting speed had recovered to match that of control fish. Among individuals, however, maximum sprinting speed was negatively correlated with growth rate after the resumption of feeding. This suggests that the rapid compensatory growth that occurs during re-feeding after a prolonged fast carries a physiological cost in terms of reduced sprinting capacity, the extent of which shows continuous variation among individuals in relation to growth rate. The long-term repeatability of maximum sprint speed was low when fish were fasted or fed a maintenance ration, but was high among control fish fed to satiation. Fish that had been previously food deprived continued to show low repeatability in sprinting ability even after the initiation of ad libitum feeding, probably stemming from variation in compensatory growth among individuals and its associated negative effects on sprinting ability. Together these results suggest that food limitation can disrupt hierarchies of maximum sprint performance within populations. In the wild, the cumulative effects on locomotor capacity of fasting and re-feeding could lead to variable survival among individuals with different growth trajectories following a period of feed deprivation.
Crystal Structure of 1,3-Dimethylimidazolium Bis(fluorosulfonyl)amide: Unexpectedly High Melting Point Arising from Polydentate Hydrogen Bonding
Authors: Fujii Kozo , Mukai Tomohiro , Nishikawa Keiko
Published: November 2013

1,3-Dimethylimidazolium bis(fluorosulfonyl)amide, [C1mim]FSA, is an ionic liquid with a lower viscosity than the bis(trifluoromethanesulfonyl)amide salt, [C1mim]NTf2, but with a higher melting point. The single-crystal X-ray structure analysis reveals that this is because the [C1mim]FSA crystal has low coordination ion number and three types of highly symmetric polydentate C–H···O hydrogen bonds.
Role of multi-detector computed tomography (MDCT) in management of post percutaneous nephrolithotomy (PCNL) bleeding
Authors: Ganpule Arvind P , Shah Darshan H , Ganpule Sanika A , Sabnis Ravindra B , Rajapurkar Mohan M , Desai Mahesh R
Published: November 2013

Objective: To evaluate the role of multidetector computerized tomography (MDCT) angiography in post percutaneous nephrolithotomy (PCNL) bleed and compare findings with conventional angiography (CA).

Material and methods: We conducted a retrospective analysis of patients who had post PCNL bleeding and subsequently underwent a MDCT angiography followed by CA. We reviewed eight patients, who presented between January 2009 and January 2013. We performed a MDCT angiography on a 16 slice GE bright speed CT scanner. All angiographies were done by using the Digital Subtraction Angiography Suite. The angioembolisation, if required, was conducted by an interventional nephrologist, specializing in therapeutic embolisation.

Results: The mean age of the patients was 42±17 years. Mean time of post PCNL bleed presentation was 10.06±7.9 days. Five patients presented with aneurysm and three presented with an AV fistula with pseudoaneurysm. The right renal unit was involved in six cases and the left in two cases. The lower polar segmental artery was involved in six cases and the upper polar artery in two cases. The CA and MDCT findings matched in all cases and the MDCT helped the clinician to assess and embolise the appropriate arterial tree.

Conclusion: MDCT is rapid, reproducible and noninvasive. MDCT angiography performed in the setting of post PCNL bleeding provides an accurate assessment of the site and nature of bleeding. The MDCT angiography matched the CA findings in all patients in the present study.
Will the Global Village Fracture Into Tribes? Recommender Systems and Their Effects on Consumer Fragmentation
Authors: Hosanagar Kartik , Fleder Daniel , Lee Dokyun , Buja Andreas
Published: November 2013

Personalization is becoming ubiquitous on the World Wide Web. Such systems use statistical techniques to infer a customer's preferences and recommend content best suited to him (e.g., “Customers who liked this also liked…”). A debate has emerged as to whether personalization has drawbacks. By making the Web hyperspecific to our interests, does it fragment Internet users, reducing shared experiences and narrowing media consumption? We study whether personalization is in fact fragmenting the online population. Surprisingly, it does not appear to do so in our study. Personalization appears to be a tool that helps users widen their interests, which in turn creates commonality with others. This increase in commonality occurs for two reasons, which we term volume and product-mix effects. The volume effect is that consumers simply consume more after personalized recommendations, increasing the chance of having more items in common. The product-mix effect is that, conditional on volume, consumers buy a more similar mix of products after recommendations.

This paper was accepted by Sandra Slaughter, information systems.
Management Insights
Authors: Gorman Michael F.
Published: November 2013

In our monthly Management Insights we highlight—without using technical jargon—the insights and implications for practicing managers that are explored and developed in each article published in the issue.
Manna from heaven: Refuse from an arboreal ant links aboveground and belowground processes in a lowland tropical forest
Authors: Clay Natalie A. , Lucas Jane , Kaspari Michael , Kay Adam D.
Published: November 2013

Aboveground consumers can shape belowground processes by serving as conduits for resources. Social insects dominate in terms of biomass in tropical forests, but compared to studies on large mammals, or aggregate solitary insects, we know relatively little about the role of social insects as nutrient conduits particularly in complex environments like tropical forests. Social insects like ants in the tropical forest canopy can connect aboveground and belowground food webs by producing a nutrient stream (excreta) from large, long‐lived and stationary nests. The excreta, in turn, would create enduring spatial heterogeneity in the forest floor. Here we evaluate this scenario in a lowland Neotropical forest using Azteca trigona, a dominant canopy ant that feeds on honeydew and insects and rains refuse out of its hanging nests onto the leaf litter below. We investigate decomposition rates and detrital communities associated with areas near nests versus 10 m away. Further, we directly test refuse's impact on decomposition and detrital communities in a common garden experiment. Relative to leaf litter, refuse is enriched 7‐fold in P, 23‐fold in K, and 3‐fold in N, all elements shown to limit decomposition in this forest. Accordingly, both artificial substrates and natural leaf litter substrates decomposed over 1.5‐ and 1.2‐fold faster respectively below A. trigona nests and areas under nests supported more invertebrate detritivores and predators compared to controls 10 m away. These decomposition results were replicated in a 6‐wk common garden experiment, but the changes in detrital invertebrate composition were not. Canopy ants like A. trigona act as dependable nutritional conduits to patches of the forest floor, transferring significant quantities of aboveground exudates and necromass. The general capacity for such social insect colonies to generate ecosystem heterogeneity remains an open question.
Shade, nutrients, and grass competition are important for tree sapling establishment in a humid savanna
Authors: Vadigi Snehalatha , Ward David
Published: November 2013

The structure and function of savannas is contingent upon tree sapling establishment into the ecosystem. Frequent rainfall, canopy shade and nutrient availability are the main factors influencing recruitment of tree saplings. Grass competition has potential to change the tree establishment dynamics by interacting with these factors. The factors affecting tree sapling establishment have been well studied and tested in arid and semi‐arid environments (approx. 0.350–0.750 m mean annual precipitation [MAP]) compared to humid (>1.000 m MAP) savanna ecosystems. We studied the effects of water (frequent irrigation vs. rainfall), shade (presence vs. absence), nutrients (addition vs. no addition) and grass competition (presence vs. absence) on sapling survival and functional traits related to growth and size of four dominant humid savanna species and four dominant mesic savanna species (approx. 0.750 m MAP), under controlled field conditions in a humid South African savanna. None of the treatments had an effect on sapling survival. Growth of the saplings did not depend on the frequency of watering, probably due to high rainfall received in humid savannas. Shade had a strong negative effect on sapling growth, suppressing the beneficial effects of nutrient availability and absence of grass competition. Net positive effects of nutrient availability had less influence over sapling growth than the negative effects exerted by grass competition. Overall shoot growth increased with nutrient addition while investment in leaves drastically declined with grass competition. We conclude that canopy shade is a strong potential driver of structure and function of humid savanna ecosystems, although we recognize that nutrient limitation and grass competition additionally influence tree sapling establishment.
Soil respiration in a northeastern US temperate forest: a 22‐year synthesis
Authors: Giasson M.-A. , Ellison A. M. , Bowden R. D. , Crill P. M. , Davidson E. A. , Drake J. E. , Frey S. D. , Hadley J. L. , Lavine M. , Melillo J. M. , Munger J. W. , Nadelhoffer K. J. , Nicoll L. , Ollinger S. V. , Savage K. E. , Steudler P. A. , Tang J. , Varner R. K. , Wofsy S. C. , Foster D. R. , Finzi A. C.
Published: November 2013

To better understand how forest management, phenology, vegetation type, and actual and simulated climatic change affect seasonal and inter‐annual variations in soil respiration (Rs), we analyzed more than 100,000 individual measurements of soil respiration from 23 studies conducted over 22 years at the Harvard Forest in Petersham, Massachusetts, USA. We also used 24 site‐years of eddy‐covariance measurements from two Harvard Forest sites to examine the relationship between soil and ecosystem respiration (Re).

Rs was highly variable at all spatial (respiration collar to forest stand) and temporal (minutes to years) scales of measurement. The response of Rs to experimental manipulations mimicking aspects of global change or aimed at partitioning Rs into component fluxes ranged from −70% to +52%. The response appears to arise from variations in substrate availability induced by changes in the size of soil C pools and of belowground C fluxes or in environmental conditions. In some cases (e.g., logging, warming), the effect of experimental manipulations on Rs was transient, but in other cases the time series were not long enough to rule out long‐term changes in respiration rates. Inter‐annual variations in weather and phenology induced variation among annual Rs estimates of a magnitude similar to that of other drivers of global change (i.e., invasive insects, forest management practices, N deposition). At both eddy‐covariance sites, aboveground respiration dominated Re early in the growing season, whereas belowground respiration dominated later. Unusual aboveground respiration patterns—high apparent rates of respiration during winter and very low rates in mid‐to‐late summer—at the Environmental Measurement Site suggest either bias in Rs and Re estimates caused by differences in the spatial scale of processes influencing fluxes, or that additional research on the hard‐to‐measure fluxes (e.g., wintertime Rs, unaccounted losses of CO2 from eddy covariance sites), daytime and nighttime canopy respiration and its impacts on estimates of Re, and independent measurements of flux partitioning (e.g., aboveground plant respiration, isotopic partitioning) may yield insight into the unusually high and low fluxes. Overall, however, this data‐rich analysis identifies important seasonal and experimental variations in Rs and Re and in the partitioning of Re above‐ vs. belowground.
Safely Exceeding Buckling Loads in Long Horizontal Wells: Case Study in Shale Plays
Authors: Menand S.. , Chen D.C.K.. C.K.
Published: November 2013

Drilling operations face several limits that intensify uncertainty and risks. Because of the deeper and/or longer wells, drilling equipment is pushed to its mechanical and endurance limits. The general industry perception is that when drillstrings or casing strings exceed conventional helical-buckling criteria, they cannot be operated safely in the hole because the risk of failure or lockup is too high. However, some theoretical, experimental, and field case studies have shown that tubular may be run in the hole even in a buckling state, within safe limits. This paper shows a case study in long horizontal wells for which helical-buckling load has been exceeded without compromising the success of the operations.

Drilling data from Bakken field in North Dakota have been gathered, analyzed, and compared with an advanced drillstring-mechanics model that enables simultaneous calculation of torque, drag, and buckling. A strong focus has been placed on the comparison between conventional buckling criteria and drillpipe (DP) or tubular bending stresses. Field results supported by drillstring modeling suggest that the helical-buckling load has been exceeded during operation at some locations along the drillstring during slide drilling and liner running but with bending stresses at an acceptable level. However, in rotary drilling, buckling should be avoided because it will create high vibrations. In this case study, the effect of drillstring dynamics is not considered.
Nattokinase production: Medium components and feeding strategy studies
Authors: Berenjian Aydin , Mahanama Raja , Kavanagh John , Dehghani Fariba , Ghasemi Younes
Published: November 2013

In the present study, the effect of nutrients on nattokinase activity during
the fermentation of Bacillus subtilis natto was investigated. The highest
nattokinase activity of 587 U/mL was obtained in fermenter for a media
consisting of yeast extract (6%, w/v), soy peptone (1.2%, w/v) and glycerol
(6%, w/v). The second order polynomial equation was fitted to the results by
using central composite face design. The polynomial model fitted the
experimental data well with R2 = 0.939 and R2(Adj) = 0.861. In addition,
contribution of fed-batch glycerol addition on the nattokinase production
pathway was further investigated. Maximum nattokinase activity was resulted
when 3% (w/v) glycerol was added to the fermentation media during the cell
growth phase. Results demonstrate 25 fold increase of nattokinase activity
compared to the batch and not optimized culture. This study provides valuable
data on the key nutrients and feeding strategy for further investigations and
scale up of nattokinase production process.
Economizer water-wall damages initiated by feedwater impurities
Authors: Vidojkovic Sonja , Onjia Antonije , Devecerski Aleksandar , Grahovac Nebojsa , Nastasovic Aleksandra
Published: November 2013

The main causes of efficiency loss in thermal power plants are boiler tube
failures that diminish unit reliability and availability, and raise the cost
of the electric energy. For that reason, regular examination of boiler tubes
is indispensable measure for prevention future malfunctions of power units.
Microscopic examination of economizer inner wall microstructure, analysis of
chemical composition of deposit using x-ray diffraction (XRD) and scanning
electron microscopy/energy dispersive spectroscopy (SEM/EDS) has been
performed in a subcritical power plant. Stress corrosion cracking, pitting
corrosion, destroyed protective magnetite layer, presence of magnetite and
hematite in deposit and corrosive impurities within the cracks were indicated
the effect of inadequate quality of feedwater that can not entirely ensure
reliable operation of the boiler. It may be stated that maintenance of
present boiler does not provide its reliable operation. Extensive chemical
control of water/steam cycle was recommended.
Demand Uncertainty and Cost Behavior
Authors: Banker Rajiv D. , Byzalov Dmitri , Plehn-Dujowich Jose M.
Published: November 2013

We investigate analytically and empirically the relationship between demand uncertainty and cost behavior. We argue that with more uncertain demand, unusually high realizations of demand become more likely. Accordingly, firms will choose a higher capacity of fixed inputs when uncertainty increases in order to reduce congestion costs. Higher capacity levels imply a more rigid short-run cost structure with higher fixed and lower variable costs. We formalize this “counterintuitive” argument in a simple analytical model of capacity choice. Following this logic, we hypothesize that firms facing higher demand uncertainty have a more rigid short-run cost structure with higher fixed and lower variable costs. We test this hypothesis for the manufacturing sector using data from Compustat and the NBER-CES Industry Database. Evidence strongly supports our hypothesis for multiple cost categories in both datasets. The results are robust to alternative specifications.

Data Availability: All data used in this study are available from public sources.
Le rôle de l’aspect lexical et de la fréquence des formes dans l’input sur la production des formes du passé par des enfants apprenants du français L2 en début d’acquisition
Authors: Thomas Anita
Published: November 2013

Résumé :

L’objectif de cette étude est d’examiner le rôle de l’aspect lexical et de la fréquence des formes dans l’input dans la production orale des formes du passé par des enfants suédois (âgés de 4 à 9 ans) apprenants du français langue seconde (L2) en immersion. Le rôle de la fréquence dans l’input est souvent négligé dans les études sur l’influence de l’aspect lexical tout comme les caractéristiques spécifiques des verbes le sont dans les études consacrées à l’influence de la fréquence des formes. L’analyse de 21 verbes dans l’input puis dans la production des cinq enfants durant les deux premières années d’exposition au français montre un recoupement entre les deux facteurs. Bien que les enfants produisent la plupart des verbes selon leur aspect lexical, les fréquences type et d’occurrence dans l’input permettent d’expliquer à la fois le marquage correct du passé ainsi que la variation que l’on trouve dans les groupes de verbes étudiés. Les résultats confirment ainsi les prédictions d’une approche basée sur l’usage selon laquelle les apprenants construisent leur grammaire à partir de leur expérience de l’input.
Frequency and predictors of complications in neurological surgery: national trends from 2006 to 2011
Authors: Rolston John D. , Han Seunggu J. , Lau Catherine Y. , Berger Mitchel S. , Parsa Andrew T.
Published: November 2013

Object

Surgical complications increase the cost of health care worldwide and directly contribute to patient morbidity and mortality. In an effort to mitigate morbidity and incentivize best practices, stakeholders such as health insurers and the US government are linking reimbursement to patient outcomes. In this study the authors analyzed a national database to determine basic metrics of how comorbidities specifically affect the subspecialty of neurosurgery.

Methods

Data on 1,777,035 patients for the years 2006–2011 were acquired from the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database. Neurosurgical cases were extracted by querying the data for which the surgical specialty was listed as “neurological surgery.” Univariate statistics were calculated using the chi-square test, and 95% confidence intervals were determined for the resultant risk ratios. A multivariate model was constructed using significant variables from the univariate analysis (p < 0.05) with binary logistic regression.

Results

Over 38,000 neurosurgical cases were analyzed, with complications occurring in 14.3%. Cranial cases were 2.6 times more likely to have complications than spine cases, and African Americans and Asians/Pacific Islanders were also at higher risk. The most frequent complications were bleeding requiring transfusion (4.5% of patients) and reoperation within 30 days of the initial operation (4.3% of patients), followed by failure to wean from mechanical ventilation postoperatively (2.5%). Significant predictors of complications included preoperative stroke, sepsis, blood transfusion, and chronic steroid use.

Conclusions

Understanding the landscape of neurosurgical complications will allow better targeting of the most costly and harmful complications of preventive measures. Data from the ACS NSQIP database provide a starting point for developing paradigms of improved care of neurosurgical patients.