bluuebunny/crossref_metadata_2025 huggingface dataset:
The bioethical experiences of student dietitians on their final clinical placement
Authors: Tighe B. , Mainwaring J.
Published: November 2012

Background

Dietetic students are exposed to bioethical dilemmas on clinical placements; however, the nature of these situations has not been investigated. The present study aimed to analyse students' reports of incidents and their associated personal development plans (PDP) to assess the type of ethical incidents faced and how they cope with them.

Methods

Final‐year dietetic students were recruited via an announcement in class. The students' PDPs were analysed using thematic analysis to identify the type of ethical issues faced and how they felt about them. The 500‐word PDPs were submitted after the final placement.

Results

Thirteen (13/26) students identified ‘ethics’ as a learning need and most of these incidents were related to enteral feeding (10/13). Ethical issues identified related to nonmaleficence; best interest; consent and capacity; truth telling and integrity; autonomy and substituted decision‐making; futile treatment; beneficence and confidentially. The themes for how the students coped included being unsure; lack of confidence or knowledge with ethics and/or with communication; lack of experience; unease/concern about shared decision‐making; and their own role in the situation.

Conclusions

Student dietitians are exposed to a wide range of complex ethical clinical situations, with those related to enteral feeding being the most common. Students felt unsure of what to do and lacked confidence, which resulted in unease and concern; however, students appeared to have some ethical sensitivity. Communication problems with the multidisciplinary team or families were a common theme. Clinical educators need to support students in these situations and act as role models.
Arcuate Nucleus Homeostatic Systems are Not Altered Immediately Prior to the Scheduled Consumption of Large, Binge‐Type Meals of Palatable Solid or Liquid Diet in Rats and Mice
Authors: Bake T. , Duncan J. S. , Morgan D. G. A. , Mercer J. G.
Published: November 2012

Meal feeding is a critical issue in the over‐consumption of calories leading to human obesity. To investigate the mechanisms involved in the regulation of meal feeding in rodents, we studied a scheduled feeding regime that induces substantial food intake over short periods of time. Male Sprague–Dawley rats and C57BL6 mice were fed one of four palatable diets [45% fat pellet, 60% fat pellet or standard pellet supplemented with Ensure (EN; Abbott Laboratories, Maidenhead, UK) or 12.5% sucrose (SUC)] either ad lib. or with daily 2‐h scheduled access and standard pellet available for 22 h. Energy balance gene expression in the hypothalamic arcuate nucleus (ARC) and nucleus accumbens (NAcc) reward gene expression were assessed by in situ hybridisation. Rats fed ad lib. on 45% or 60% fat diet were heavier and fatter than controls, and had reduced neuropeptide Y (NPY) gene expression in the ARC. Mice fed ad lib. on any of the palatable diets were heavier, fatter and had higher blood leptin than controls, and had reduced NPY and increased cocaine‐ and‐amphetamine‐regulated transcript mRNA in the ARC. Schedule‐fed rats and mice quickly adapted their feeding behaviour to 2‐h access on palatable food. Three schedule‐fed groups binged: the percentage of daily calories consumed in 2 h on 45% fat diet, 60% fat diet or EN, respectively, was 55%, 63% and 49% in rats, and 86%, 86% and 45% in mice. However, changed feeding behaviour was not reflected in an induction of orexigenic neuropeptide or suppression of anorexigenic neuropeptide gene expression in the ARC, in the 2‐h period prior to scheduled feeding. The mechanisms underlying large meal/binge‐type eating may be regulated by nonhomeostatic processes involving other genes in the hypothalamus or other brain areas. However, assessment of opioid and dopamine receptor gene expression in the NAcc did not reveal evidence of the involvement of these genes in driving large meals, at least at the investigated time point.
Dynamics of Harvest Subcontracting: The Roles Played by Labour Contractors
Authors: Ortiz Sutti , Aparicio Susana , Tadeo Nidia
Published: November 2012

A historical perspective of three export agro‐industries inArgentina (lemons, sweet citrus and tobacco) illustrates the range of factors that may foster subcontracting and the choice of subcontracting modalities. The case studies also illustrate that subcontracting is often a fragile strategy that leads to the eventual reabsorption of subcontracted tasks. We argue that the fragility of subcontracting the harvest rests on the inability of producers and labour contractors to negotiate a relationship that favours collaboration and problem solving. This failure is at the root of the high transaction costs of harvest subcontracting that force producers to resort to ancillary investments or sanctions, or to reabsorb some or all of the delegated tasks. A mismatch of resources and technical competence between producers and harvest labour contractors also contributes to inadequate performance of services. It is thus not surprising that harvest labour contractors are not always permanent fixtures; they may appear, disappear and reappear, particularly in fresh fruit export industries.
Stress, Social Support, and Depression: A Test of the Stress‐Buffering Hypothesis in a Mexican Sample
Authors: Raffaelli Marcela , Andrade Flavia C. D. , Wiley Angela R. , Sanchez‐Armass Omar , Edwards Laura L. , Aradillas‐Garcia Celia
Published: November 2012

This study examined social support as a potential moderator between stress and depressive symptoms among Mexican university applicants aged 16–21 years (N = 6,715; M age = 17.9 years; 55% female). In bivariate analyses, perceived stress was associated with higher levels of depressive symptoms, and social support with lower levels of both stress and depression. Moderation analyses conducted using hierarchical multiple regressions indicated that global social support reduced the association between stress and depression. Analyses examining support from different sources (family, friends, and significant other) indicated that family support played a unique role in buffering the negative effects of stress. Findings are consistent with the stress‐buffering hypothesis and confirm the importance of the family as Mexican youth enter late adolescence.
Differential regulation of collagen, lysyl oxidase and MMP‐2 in human periodontal ligament cells by low‐ and high‐level mechanical stretching
Authors: Chen Y‐J. , Jeng J‐H. , Chang H‐H. , Huang M‐Y. , Tsai F‐F. , Jane Yao C‐C.
Published: November 2012

Background and Objective

Mechanical stretching modulates extracellular matrix (ECM) protein synthesis by periodontal ligament (PDL) cells. However, the mechanoregulation of lysyl oxidase (LOX), a key enzyme for collagen cross‐linking, is not fully understood. In the present study, we hypothesized that low‐level and high‐level mechanical stretching differentially regulates collagen deposition and the expression of LOX and the enzymes responsible for ECM degradation, such as MMP‐2 in PDL cells.

Material and Methods

Human PDL cells were cultured on flexible‐bottom culture plates and subjected to cyclic mechanical stretching (3% and 10% elongation at 0.1 Hz) for 24 and 48 h in a Flexercell FX‐4000 strain unit. The levels of expression of type I collagen alpha 1 (COL1A1), type III collagen alpha 1 (COL3A1), lysyl oxidase (LOX), MMP2 and TIMP2 mRNAs were analyzed using an RT‐PCR technique. The cell layer and the culture medium were separately collected and processed for detection of the following ECM‐related molecules: (i) total collagen content using a Sircol dye‐binding method; (ii) LOX protein expression by western blotting; (iii) LOX activity using a fluorometric assay; and (iv) MMP‐2 enzyme activity by gelatin zymography.

Results

Low‐level (3%) mechanical stretching of PDL cells upregulated the expression of COL1A1, COL3A1 and LOX mRNAs, enhanced the production of collagen and increased the LOX activity but did not change the level of expression of MMP2 or TIMP2 mRNA. The collagen content and LOX activity showed obvious elevation in the medium, but not in the cell layer. High‐level (10%) mechanical stretching downregulated COL1A1 mRNA but upregulated COL3A1 mRNA; however, the effect on COL3A1 was smaller, and occurred earlier, compared with the effect on the COL1A1 gene. High‐level mechanical stretching upregulated the expression of MMP2 and TIMP2 mRNAs but did not change collagen production or LOX activity. Moreover, high‐level mechanical stretching increased the level of pro‐MMP‐2, especially in the cell layer.

Conclusions

This study substantiates the mechanoregulation of the expression of ECM‐related molecules in PDL cells. High‐level mechanical stretching upregulated the expression of MMP2 and TIMP2 mRNAs, but did not affect collagen production or LOX activity. In addition to increasing the transcription of COL1A1, COL3A1 and LOX genes, low‐level mechanical stretching enhanced total collagen production and LOX activity, which should favor ECM stabilization. As an effective regulator of ECM remodeling, mechanical stretching can be exploited in periodontal regeneration and ligament tissue engineering via application of appropriate mechanical stimulation.
Echocardiographic Evidence of Left Ventricular Hypertrophy in Obese Dogs
Authors: Mehlman E. , Bright J.M. , Jeckel K. , Porsche C. , Veeramachaneni D.N.R. , Frye M.
Published: November 2012

Background

Cardiomyopathy of obesity occurs in humans, but the gross and cellular myocardial response to obesity in dogs is not well defined.

Objectives

To characterize in vivo myocardial morphology and function in normotensive obese dogs, and quantitate collagen, triglyceride and myocyte cross‐sectional area (CSA) in postmortem tissues from obese dogs.

Animals

Echocardiographic‐Doppler measurements of normotensive obese dogs (n = 19) without historical or physical examination evidence of disease, and lean healthy dogs (n = 19) matched for age and ideal weight. Postmortem data were obtained from a separate population of 4 obese and 12 lean dogs without evidence of cardiac disease.

Methods

A prospective, observational study of myocardial morphology and function was conducted by echocardiographic‐Doppler measurement. Left ventricular (LV) tissue was collected for quantitation of triglyceride, collagen, and myocyte CSA.

Results

Compared with lean control dogs, obese dogs had increased systolic blood pressure (obese 153 ± 19 mm Hg; lean 133 ± 20 mm Hg;P = .003), and increased LV free wall thickness at end‐diastole (obese 9.9 ± 1.8 mm, lean 8.7 ± 1.5 mm;P = .03) and end‐systole (obese 15.2 ± 2.3 mm, lean 12.9 ± 2.3 mm;P = .004). Isovolumic relaxation time was prolonged in 7/19 (37%) of obese dogs, compared with normal ranges. Myocardial triglyceride and collagen content and myocyte CSA were similar between groups.

Conclusions and Clinical Importance

As in humans, LV hypertrophy and diastolic dysfunction can be an early myocardial change in some obese dogs.
On the perception, production and function of blue colouration in animals
Authors: Umbers Kate D. L.
Published: November 2012

Bright colouration in animals has long attracted the attention of physicists, chemists and biologists. As such, studies on the functions of colours are interdisciplinary, focusing on the mechanisms of colour production and maintenance, the physical and chemical properties of the colour‐producing elements, and visual systems and behaviour of potential receivers. Blue colouration has received a large share of research attention and is fascinating for several reasons: blue has been attributed to a very broad range of functions, blue is achieved by a great variety of mechanisms (although their production and maintenance costs are currently unclear), and the blue part of the spectrum (450–490 nm) can be perceived by most taxa. This review explores the breadth of studies that propose a function for blue colouration. In so doing, it discusses the diversity of ways in which blue colours are produced both as pigments and structural colours, and that blue visual pigments are common across a broad range of taxa. This analysis of the current literature emphasizes the importance of multidisciplinary hypothesis testing when attempting to elucidate the function of colours, the need for manipulative over correlative evidence for the function of colours, and, as colour research becomes evermore interdisciplinary, the need for well‐defined consistent terminology.
Outlier loci highlight the direction of introgression in oaks
Authors: Guichoux E. , Garnier‐Géré P. , Lagache L. , Lang T. , Boury C. , Petit R. J.
Published: November 2012

Loci considered to be under selection are generally avoided in attempts to infer past demographic processes as they do not fit neutral model assumptions. However, opportunities to better reconstruct some aspects of past demography might thus be missed. Here we examined genetic differentiation between two sympatricEuropean oak species with contrasting ecological dynamics (Quercus roburandQuercus petraea) with both outlier (i.e. loci possibly affected by divergent selection between species or by hitchhiking effects with genomic regions under selection) and nonoutlier loci. We sampled 855 individuals in six mixed forests inFrance and genotyped them with a set of 262SNPs enriched with markers showing high interspecific differentiation, resulting in accurate species delimitation. We identified between 13 and 74 interspecific outlier loci, depending on the coalescent simulation models and parameters used. Greater genetic diversity was predicted inQ. petraea(a late‐successional species) than inQ. robur(an early successional species) as introgression should theoretically occur predominantly from the resident species to the invading species. Remarkably, this prediction was verified with outlier loci but not with nonoutlier loci. We suggest that the lower effective interspecific gene flow at loci showing high interspecific divergence has better preserved the signal of past asymmetric introgression towardsQ. petraeacaused by the species' contrasting dynamics. Using markers under selection to reconstruct past demographic processes could therefore have broader potential than generally recognized.
Does mating behaviour affect connectivity in marine fishes? Comparative population genetics of two protogynous groupers (Family Serranidae)
Authors: Portnoy D. S. , Hollenbeck C. M. , Renshaw M. A. , Cummings N. J. , Gold J. R.
Published: November 2012

Pelagic larval duration (PLD) has been hypothesized to be the primary predictor of connectivity in marine fishes; however, few studies have examined the effects that adult reproductive behaviour may have on realized dispersal. We assessed gene flow (connectivity) by documenting variation in microsatellites and mitochondrial DNA sequences in two protogynous species of groupers, the aggregate spawning red hind, Epinephelus guttatus, and the single‐male, harem‐spawning coney, Cephalopholis fulva, to ask whether reproductive strategy affects connectivity. Samples of both species were obtained from waters off three islands (Puerto Rico, St. Thomas and St. Croix) in the Caribbean Sea. Despite the notion that aggregate spawning of red hind may facilitate larval retention, stronger signals of population structure were detected in the harem‐spawning coney. Heterogeneity and/or inferred barriers, based on microsatellites, involved St. Croix (red hind and coney) and the west coast of Puerto Rico (coney). Heterogeneity and/or inferred barriers, based on mitochondrial DNA, involved St. Croix (coney only). Genetic divergence in both species was stronger for microsatellites than for mitochondrial DNA, suggesting sex‐biased dispersal in both species. Long‐term migration rates, based on microsatellites, indicated asymmetric gene flow for both species in the same direction as mean surface currents in the region. Red hind had higher levels of variation in microsatellites and lower levels of variation in mitochondrial DNA. Long‐term effective size and effective number of breeders were greater for red hind; estimates of θf, a proxy for long‐term effective female size, were the same in both species. Patterns of gene flow in both species appear to stem in part from shared aspects of larval and adult biology, local bathymetry and surface current patterns. Differences in connectivity and levels of genetic variation between the species, however, likely stem from differences in behaviour related to reproductive strategy.
Phosphatidylglycerophosphate synthase associates with a mitochondrial inner membrane complex and is essential for growth of Trypanosoma brucei
Authors: Serricchio Mauro , Bütikofer Peter
Published: November 2012

Maintenance of the lipid composition is important for proper function and homeostasis of the mitochondrion. In Trypanosoma brucei, the enzymes involved in the biosynthesis of the mitochondrial phospholipid, phosphatidylglycerol (PG), have not been studied experimentally. We now report the characterization of T. brucei phosphatidylglycerophosphate synthase (TbPgps), the rate‐limiting enzyme in PG formation, which was identified based on its homology to other eukaryotic Pgps. Lipid quantification and metabolic labelling experiments show that TbPgps gene knock‐down results in loss of PG and a reduction of another mitochondria‐specific phospholipid, cardiolipin. Using immunohistochemistry and immunoblotting of digitonin‐isolated mitochondria, we show that TbPgps localizes to the mitochondrion. Moreover, reduced TbPgps expression in T. brucei procyclic forms leads to alterations in mitochondrial morphology, reduction in the amounts of respiratory complexes III and IV and, ultimately, parasite death. Using native polyacrylamide gel electrophoresis we demonstrate for the first time in a eukaryotic organism that TbPgps is a component of a 720 kDa protein complex, co‐migrating with T. brucei cardiolipin synthase and cytochrome c1, a protein of respiratory complex III.
Analysis of Two Kinds of Tree as Physical Barriers Against Erythemal UVB Radiation Received
Authors: Ysasi Gonzalo G. , Ribera Luis J. C.
Published: November 2012

Differences between global radiation UVER (erythemal ultraviolet solar radiation) received under full sun and diffuse radiation received under the shadow of two types of tree are analyzed to check the importance of these components on human exposure to UV radiation. Blue Line spores dosimeters of VioSpor were used for measurement of erythemal dose of UV radiation (able to produce erythema in human skin.) The response profile of these devices is extremely similar to human skin, thus they are suitable to determine and predict the interactions between UV erythema and human skin. Measurements were obtained in relatively clear days from February to December 2009 between 9:30 and 15:30 h. Three dosimeters were placed on a horizontal surface: one in full sun and the other two under the shadow of each tree. Values of UVER in both cases, in full sun and under the shadow of pine and Sauce, were obtained. In addition, the comparison was made between values of dose received in each case and the exposure limits recommended by the International Commission on Non‐Ionizing Radiation Protection (ICNIRP). Finally, average daily irradiance received under the shadow of each tree in comparison with those received in full sun, was also analyzed using two PMA2100 radiometers situated on a horizontal surface.
The Bovine Luteal Histological Composition: A Topographic Point of View
Authors: Cools S , Van den Broeck W , De Vliegher S , Piepers S , Opsomer G
Published: November 2012

Contents

High‐yielding dairy cows are struggling with a high incidence of embryonic loss, among others caused by an insufficient peripheral progesterone concentration which for its part might be associated with an impaired luteal progesterone production. This impaired capacity to produce progesterone might be reflected in the histology of the gland. The aim of the present pilot study was the assessment of the variation in cell density within a bovine luteal gland (LG), to examine whether it is possible to analyse histologically the functionality of the gland based on one single tissue sample. Six LGs (stage II or III) were harvested out of just as many healthy cows at the slaughterhouse. The luteal cell density was assessed by calculating the nuclear density (ND) of the different luteal cell types on haematoxylin‐eosin‐stained histological sections from a number of topographic regions evenly spread throughout the glands, to give an overview of the pattern of cellular distribution within the whole gland. Cells were differentiated into ‘large luteal cells’, ‘small luteal cells’ and ‘non‐steroidogenic cells’. Results show that the cellular density, within a tissue sample is not significantly influenced by its location in relation to the gland's equatorial plane. However, the position with respect to the polar axis of the gland has a decisive effect, as the ND is significantly higher (p < 0.05) in the peripheral regions (outer zone) when compared with the central regions (inner zone) of the gland, and this counts for all three cell types.
Deprivation and Subjective Well‐Being: Evidence from Panel Data
Authors: Cuesta Maite Blázquez , Budría Santiago
Published: November 2012

This paper uses data from the 2000–08 waves of the German Socio‐Economic Panel dataset (SOEP) to assess the impact of deprivation in various life domains upon individual well‐being. Unobserved heterogeneity is controlled for by means of a random effects model extended to include a Mundlak term and explicit controls for the respondents' personality traits. The paper shows that people care about social comparison information in a number of domains, not just income. Using an equivalent income approach, the estimates suggest that a one standard deviation deterioration of the individual position in the income distribution is as important as a 33.5 percent decrease in own income. This monetary equivalent amounts to an income variation of between 25 and 43 percent when it comes to other deprivation domains, including durables, accommodation, health, and social relations. These results recommend that in the fight against deprivation more emphasis should be directed to these non‐monetary relevant dimensions.
High levels of jasmonic acid antagonize the biosynthesis of gibberellins and inhibit the growth of Nicotiana attenuata stems
Authors: Heinrich Maria , Hettenhausen Christian , Lange Theo , Wünsche Hendrik , Fang Jingjing , Baldwin Ian T. , Wu Jianqiang
Published: November 2012

Hormones play pivotal roles in regulating plant development, growth, and stress responses, and cross‐talk among different hormones fine‐tunes various aspects of plant physiology. Jasmonic acid (JA) is important for plant defense against herbivores and necrotic fungi and also regulates flower development; in addition, Arabidopsis mutants over‐producing JA usually have stunted stems and wound‐induced jasmonates suppress Arabidopsis growth, suggesting that JA is also involved in stem elongation. Gibberellins (GAs) promote stem and leaf growth and modulate seed germination, flowering time, and the development of flowers, fruits, and seeds. However, little is known about the interaction between the JA and GA pathways. Two calcium‐dependent protein kinases, CDPK4 and CDPK5, are important suppressors of JA accumulation in a wild tobacco species, Nicotiana attenuata. The stems of N. attenuata silenced in CDPK4 and CDPK5 (irCDPK4/5 plants) had dramatically increased levels of JA and exhibited stunted elongation and had very high contents of secondary metabolites. Genetic analysis indicated that the high JA levels in irCDPK4/5 stems accounted for the suppressed stem elongation and the accumulation of secondary metabolites. Supplementation of GA3 to irCDPK4/5 plants largely restored normal stem growth to wild‐type levels. Measures of GA levels indicated that over‐accumulation of JA in irCDPK4/5 stems inhibited the biosynthesis of GAs. Finally, we show that JA antagonizes GA biosynthesis by strongly inhibiting the transcript accumulation of GA20ox and possibly GA13ox, the key genes in GA production, demonstrating that high JA levels antagonize GA biosynthesis in stems.
Physical and electrical characteristics of atomic-layer deposition-HfO2 films deposited on Si substrates having different silanol Si-OH densities
Authors: Molina Joel , Zuniga Carlos , Calleja Wilfrido , Rosales Pedro , Torres Alfonso , Herrera-Gomez Alberto
Published: November 2012

In this work, ultrathin HfO2 films, less than 6 nm in thickness, are deposited by atomic-layer deposition (ALD) on Si substrates that have a variable density of silanol (Si-OH) chemical bonds after oxidizing the Si surface using hot H2O2. Given the surface chemistry needed for proper ALD growth of HfO2, OH-last surfaces are needed in order to react with the Hf-based precursor during half-cycle of this reaction. The later is important for proper nucleation and uniform growth of ultrathin HfO2 by ALD. Depending on the immersion time of an initially HF-last Si surface in hot H2O2, ultrathin and nonstoichiometric chemical oxides SiOx are formed presenting a variable density of Si-OH bonds which are measured after Fourier-transform infra red spectroscopy. Following SiOx formation, HfO2 is directly deposited on these surfaces by ALD using water (H2O) and tetrakis-dimethylamino-hafnium as precursors. Metal–insulator–semiconductor (MIS) capacitors are then formed using both HfO2/Si and HfO2/SiOx/Si stacked structures and their electrical characteristics are evaluated. It is found that a variable density of Si-OH chemical bonds have an impact on the physical and electrical characteristics of these MIS structures by reducing their atomic surface roughness (Rrms) and gate leakage current density (Jg), and at the same time, increasing their flat band voltage (Vfb) for the same immersion times in H2O2. Obtaining the lowest Rrms, Jg, and Vfb are possible by using intermediate H2O2 immersion times between 4 and 8 min, which is also directly related to an intermediate Si-OH bond density.
Self‐adapting cyclic registration for motion‐compensated cone‐beam CT in image‐guided radiation therapy
Authors: Brehm Marcus , Paysan Pascal , Oelhafen Markus , Kunz Patrik , Kachelrieß Marc
Published: November 2012

Purpose:

In image‐guided radiation therapy an additional kV imaging system next to the linear particle accelerator provides information for an accurate patient positioning. However, the acquisition time of the system is much longer than the patientˈs breathing cycle due to the low gantry rotation speed. Our purpose is a cyclic registration in the context of motion‐compensated image reconstruction that provides high quality respiratory‐correlated 4D volumes for on‐board flat panel detector cone‐beam CT scans.

Methods:

Based on the small motion assumption, widely used within registration algorithms, a strategy is developed for motion estimation. In this strategy temporal restrictions are incorporated, for example, the cyclic motion patterns of respiration. The resultant cyclic registration method is to show less sensitivity on image artifacts, in particular on artifacts due to projection data sparsification. Using a new cyclic registration method a motion estimation is performed on respiratory‐correlated reconstructions, and the obtained motion vector fields are used for motion compensation.

Results:

The proposed cyclic registration is evaluated in the context of motion‐compensated image reconstruction using simulated data and patient data. Motion artifacts of 3D standard reconstructions can be significantly reduced by the resulting cyclic motion compensation. The method outperforms the respiratory‐correlated reconstructions regarding sparse‐view artifacts and maintains the high temporal resolution at the same time. Image artifacts show only minor to almost no effect on the motion estimation using the cyclic registration.

Conclusions:

The cyclic motion compensation approach provides respiratory‐correlated volumes with high image quality. The cyclic motion estimation is of such low sensitivity to sparse‐view artifacts, that it is capable to determine high quality motion vector fields based on reconstructions of low sampled data.
Modeling a falling slinky
Authors: Cross R. C. , Wheatland M. S.
Published: November 2012

A slinky is an example of a tension spring: in an unstretched state a slinky is collapsed, with turns touching, and a finite tension is required to separate the turns from this state. If a slinky is suspended from its top and stretched under gravity and then released, the bottom of the slinky does not begin to fall until the top section of the slinky, which collapses turn by turn from the top, collides with the bottom. The total collapse time tc (typically ∼0.3 s for real slinkies) corresponds to the time required for a wave front to propagate down the slinky to communicate the release of the top end. We present a modification to an existing model for a falling tension spring [Calkin, Am. J. Phys. 61, 261–264 (1993)] and apply it to data from filmed drops of two real slinkies. The modification of the model is the inclusion of a finite time for collapse of the turns of the slinky behind the collapse front propagating down the slinky during the fall. The new finite-collapse time model achieves a good qualitative fit to the observed positions of the top of the real slinkies during the measured drops. The spring constant k for each slinky is taken to be a free parameter in the model. The best-fit model values for k for each slinky are approximately consistent with values obtained from measured periods of oscillation of the slinkies.
A Large-Scale Model of the Functioning Brain
Authors: Eliasmith Chris , Stewart Terrence C. , Choo Xuan , Bekolay Trevor , DeWolf Travis , Tang Yichuan , Rasmussen Daniel
Published: November 2012

Modeling the Brain

Neurons are pretty complicated cells. They display an endless variety of shapes that sprout highly variable numbers of axons and dendrites; they sport time- and voltage-dependent ion channels along with an impressive array of neurotransmitter receptors; and they connect intimately with near neighbors as well as former neighbors who have since moved away. Simulating a sizeable chunk of brain tissue has recently become achievable, thanks to advances in computer hardware and software.

Eliasmith
et al.

(p.
1202
; see the Perspective by

Machens

) present their million-neuron model of the brain and show that it can recognize numerals, remember lists of digits, and write down those lists—tasks that seem effortless for a human but that encompass the triad of perception, cognition, and behavior.
From Acid Rain to Climate Change
Authors: Reis S. , Grennfelt P. , Klimont Z. , Amann M. , ApSimon H. , Hettelingh J.-P. , Holland M. , LeGall A.-C. , Maas R. , Posch M. , Spranger T. , Sutton M. A. , Williams M.
Published: November 2012

Updated air pollution science and policies address human health, ecosystem effects, and climate change in Europe.
Superconducting Dome in a Gate-Tuned Band Insulator
Authors: Ye J. T. , Zhang Y. J. , Akashi R. , Bahramy M. S. , Arita R. , Iwasa Y.
Published: November 2012

What Do You Know? A Dome

The superconducting dome—the appearance of a maximum in the transition temperature as a function of a tuning parameter—has been observed in compounds such as cuprates, pnictides, and heavy fermion materials and is thought of as a signature of unconventional superconductivity.

Ye
et al.

(p.
1193
) used a liquid gating technique combined with back gating to finely tune the carrier density in the band insulator MoS
2
, which allowed them to observe the formation of a dome. The unexpected finding awaits theoretical explanation but may suggest that the appearance of an optimal carrier density may be a more common occurrence than was previously thought.
Growing Latin American Science
Authors: Garcia Celia R. S. , Parodi Armando J. , Oliva Glaucius
Published: November 2012

How can a country rapidly improve its capacity in science, technology, and innovation? Invest in people, as Latin America is doing. For Brazil, supporting this effort through international exchange and increased mobility over the past year will substantially enlarge the nation's corpus of highly qualified scientists and technologists. Argentina has increased its number of doctoral fellowships and is concentrating on recruiting back Argentine investigators working abroad to advance its own basic research and industry. And in Chile, special programs have been funding fellowships to send students abroad to obtain Ph.D. degrees in science. These activities reflect the growing desire of Latin American nations to train an educated workforce in the world's best institutions and foster “globalized” science on the continent.
Tough Financial Times Bring ESA Down to Earth
Authors: Clery Daniel
Published: November 2012

Europe will be going to Mars, but not to the moon, and it will have to wait for a decision on a next-generation Ariane 6 launcher.
Raising Up a Fallen Ivory Tower
Authors: Stone Richard
Published: November 2012

Myanmar's universities, benighted after decades of isolation and neglect, are striving to make up lost ground and recover lost student bodies.
Salt and the Sea Serpent
Authors: Pennisi Elizabeth
Published: November 2012

Despite millions of years living in the ocean, sea snakes still have to watch their salt intake.
Delayed presentation of congenital diaphragmatic hernia presenting with intrathoracic gastric volvulus: a case report and review
Authors: Nayak Hemanta K , Maurya Gaurav , Kapoor Neha , Kar Premashis
Published: November 2012

Acute gastric volvulus associated with congenital diaphragmatic hernia is an unusual surgical emergency and its presentation in adulthood is extremely rare. Gastric volvulus is an uncommon condition which is difficult to diagnose and treat. This case describes a middle aged man presenting with post-traumatic acute abdomen and finally being diagnosed as a case of gastric volvulus due to congenital diaphragmatic hernia which was till now asymptomatic and undiagnosed. Clinical examination and chest x-ray was suggestive of hiatus hernia. Contrast-enhanced CT of thorax and abdomen revealed hiatus hernia and gastric volvulus. A provisional diagnosis of post-traumatic hiatus hernia with associated gastric volvulus was made and was operated on  an emergency basis. Surprisingly, the intraoperative findings revealed significant adhesions near the diaphragm suggestive of congenital diaphragmatic hernia. Hence, a diagnosis of gastric volvulus due to congenital diaphragmatic hernia was made which remained asymptomatic and undiagnosed till adulthood. He responded well to operative management and remained asymptomatic afterwards.
Hodgkin's lymphoma with cutaneous involvement
Authors: Dhull Anil Kumar , Soni Abhishek , Kaushal Vivek
Published: November 2012

We report a case of a 22-year-old previously healthy woman with Hodgkin's lymphoma who presented initially with multiple lymphadenopathy and later, with a solitary cutaneous ulcer. Unlike Non-Hodgkin's lymphoma subtypes, skin involvement of Hodgkin's lymphoma is extremely rare. The prognosis of Hodgkin's lymphoma with skin infiltration is felt to be extremely poor. Contrary to other reports, this case demonstrates that a good response with standard therapy is possible.
Comparison of British and French expatriate doctors’ characteristics and motivations
Authors: Quantin Catherine , Abbas Rachid , Hagi Mathieu , Breton Gwenaelle Le , Romestaing M , Carnet Dider
Published: November 2012

Objective

The aim of this study was to analyse the migration of doctors between the UK and France, in an attempt to identify the reasons for these migrations.

Design

This was a cross-sectional study conducted using a self-completed questionnaire.

Setting

The questionnaire was sent to all British doctors practising in France and to all French doctors practising in the UK.

Participants

The doctors were identified, thanks to official data of the National Medical Councils. There were 244 French doctors practising in the UK and 86 British doctors practising in France.

Outcome measures

A questionnaire was specifically developed for the study to determine the reasons why doctors moved to the other country and their level of satisfaction with regard to their expatriation.

Results

A total of 98 French doctors (of 244) and 40 British doctors (of 86) returned the questionnaire. The motivations of the two studied populations were different: French doctors were attracted by the conditions offered by the National Health Service, whereas British doctors were more interested in opportunities for career advancement, moved to join a husband or wife or to benefit from favourable environmental conditions. Overall, the doctors who responded considered the expatriation a satisfactory experience. After expatriation, 84% of French doctors were satisfied with their new professional situation compared with only 58% of British doctors.

Conclusions

This study, which is the first of its kind and based on representative samples, has led to a clearer understanding of the migration of doctors between France and the UK.
Capsaicin induces de-differentiation of activated hepatic stellate cell
Authors: Bitencourt Shanna , de Mesquita Fernanda C. , Caberlon Eduardo , da Silva Gabriela V. , Basso Bruno S. , Ferreira Gabriela A. , de Oliveira Jarbas R.
Published: November 2012

Hepatic stellate cells (HSC) play a key role in liver fibrogenesis. Activation of PPARγ and inhibition of fibrogenic molecules are potential strategies to block HSC activation and differentiation. A number of natural products have been suggested to have antifibrotic effects for the de-activation and de-differentiation of HSCs. The purpose of this study was to investigate the in vitro effects of capsaicin on HSC de-activation and de-differentiation. The results demonstrated that capsaicin induced quiescent phenotype in GRX via PPARγ activation. Significant decrease in COX-2 and type I collagen mRNA expression was observed in the first 24 h of treatment. These events preceded the reduction of TGF-β1 and total collagen secretion. Thus, capsaicin promoted down-regulation of HSC activation by its antifibrotic and anti-inflammatory actions. These findings demonstrate that capsaicin may have potential as a novel therapeutic agent for the treatment of liver fibrosis.
ONIOM and ab-initio calculations on the mechanism of uncatalyzed peptide bond formation
Authors: Monajemi Hadieh , Daud Mohammad Noh , Mohd. Zain Sharifuddin , Wan Abdullah Wan Ahmad Tajuddin
Published: November 2012

Finding a proper transition structure for the peptide bond formation process can lead one to a better understanding of the role of ribosome in catalyzing this reaction. Using computer simulations, we performed the potential energy surface scan on the ester bond dissociation of P-site aminoacyl-tRNA and the peptide bond formation of P-site and A-site amino acids. The full fragments of initiator tRNAimet and elongator tRNAphe are attached to both cognate and non-cognate amino acids as the P-site substrate. The A-site amino acid for all four calculations is methionine. We used ONIOM calculations to reduce the computational cost. Our study illustrates the reduced rate of peptide bond formation for misacylated tRNAimet in the absence of ribosomal bases. The misacylated elongator tRNAphe, however, did not show any difference in its PES compared with that for the phe-tRNAphe. This demonstrates the structural specification of initiator tRNAimet for the amino acids side chain.
Gambogic acid promotes apoptosis and resistance to metastatic potential in MDA-MB-231 human breast carcinoma cells
Authors: Li Chenglin , Qi Qi , Lu Na , Dai Qinsheng , Li Fanni , Wang Xiaotang , You Qidong , Guo Qinglong
Published: November 2012

Gambogic acid (GA) is considered a potent anti-tumor agent for its multiple effects on cancer cells in vitro and in vivo. Low concentrations of GA (0.3–1.2 µmol/L) can suppress invasion of human breast carcinoma cells without affecting cell viability. To get a whole profile of the inhibition on breast cancers, higher concentrations of GA and spontaneous metastatic animal models were employed. Treatment with GA (3 and 6 µmol/L) induced apoptosis in MDA-MB-231 cells and the accumulation of reactive oxygen species (ROS). Furthermore, GA induced PARP cleavage, activation of caspase-3, caspase-8, and caspase-9, as well as an increased ratio of Bax/Bcl-2. Moreover, the translocation of apoptotic inducing factor (AIF) and the release of cytochrome c (Cyt c) from mitochondria were observed, indicating that GA induced apoptosis through accumulation of ROS and mitochondrial apoptotic pathway. GA also inhibited cell survival via blocking Akt/mTOR signaling. In vivo, GA significantly inhibited the xenograft tumor growth and lung metastases in athymic BALB/c nude mice bearing MDA-MB-231 cells. Collectively, these data provide further support for the multiple effects of GA on human breast cancer cells, as well as for its potential application to inhibit tumor growth and prevent metastasis in human cancers.
My road to Damascus: how I converted to the prohormone theory and the proprotein convertases
Authors: Chrétien Michel
Published: November 2012

My desire as a young endocrinologist to improve my clinical skills through a better knowledge of hormone chemistry led me to serendipitous discoveries and unexpected horizons. The first discovery, published in 1967, revealed that peptide hormones are derived from endoproteolytic cleavages of larger precursor polypeptides. It was the foundation of the prohormone theory. Initially thought to apply to a few hormones, the theory rapidly extended to many proteins, including neuropeptides, neurotrophins, growth and transcription factors, receptors, extracellular matrix proteins, bacterial toxins, and viral glycoproteins. Its endoproteolytic activation mechanism has become a fundamental cellular process, affecting many biological functions. It implied the existence of specific endoproteolytic enzymes. These proprotein convertases were discovered in 1990. They have been shown to play a wide range of important roles in health and disease. They have opened up novel therapeutic avenues. Inactivation of PCSK9 to reduce plasma cholesterol is currently the most promising. To make this good thing even better, I recently discovered in a French Canadian family a potent PCSK9 (Gln152His) mutation that significantly lowers plasma cholesterol and should confer cardiovascular longevity. The discovery helped me to complete the loop: “From the bedside to the bench and back to the bedside.”
Memory of chirality in rebound cyclizations of α-amide radicals
Authors: Sasmal Aniruddha , Taniguchi Tsuyoshi , Wipf Peter , Curran Dennis P.
Published: November 2012

Reduction of (S)-N-(2-bromoallyl)-N-(tert-butyl)-2-methyl-3-phenylpropanamide with tributyltin hydride provides (3S,4S)-3-benzyl-1-(tert-butyl)-3,4-dimethylpyrrolidin-2-one with about 80% retention of chirality at the stereocenter adjacent to the amide carbonyl group. This memory of chirality is suggested to occur by transfer of chirality from a stereocenter to an axis, then from the axis back to a new stereocenter.
GEOMETRIC APPROACHES TO PRODUCE PROLONGATIONS FOR NONLINEAR PARTIAL DIFFERENTIAL EQUATIONS
Authors: BRACKEN PAUL
Published: November 2012

The prolongation structure of a two-by-two problem is formulated very generally in terms of exterior differential forms on a standard representation of Pauli matrices. The differential system is general without making reference to any specific equation. An integrability condition is provided which gives by construction the equation to be investigated and whose components involve the structure constants of an SU(2) Lie algebra. Along side this, a related, different kind of prolongation, a type of Wahlquist–Estabrook prolongation, over a closed differential ideal is discussed and some applications are given.
Implementing the data center energy productivity metric
Authors: Sego Landon H. , Márquez Andrés , Rawson Andrew , Cader Tahir , Fox Kevin , Gustafson William I. , Mundy Christopher J.
Published: November 2012

As data centers proliferate in size and number, the endeavor to improve their energy efficiency and productivity is becoming increasingly important. We discuss the properties of a number of the proposed metrics of energy efficiency and productivity. In particular, we focus on the Data Center Energy Productivity (DCeP) metric, which is the ratio of useful work produced by the data center to the energy consumed performing that work. We describe our approach for using DCeP as the principal outcome of a designed experiment using a highly instrumented, high-performance computing data center. We found that DCeP was successful in clearly distinguishing different operational states in the data center, thereby validating its utility as a metric for identifying configurations of hardware and software that would improve (or even maximize) energy productivity. We also discuss some of the challenges and benefits associated with implementing the DCeP metric, and we examine the efficacy of the metric in making comparisons within a data center and among data centers.
Barely alive memory servers
Authors: Anagnostopoulou Vlasia , Biswas Susmit , Saadeldeen Heba , Savage Alan , Bianchini Ricardo , Yang Tao , Franklin Diana , Chong Frederic T.
Published: November 2012

Current resource provisioning schemes in Internet services leave servers less than 50% utilized almost all the time. At this level of utilization, the servers' energy efficiency is substantially lower than at peak utilization. A solution to this problem could be dynamically consolidating workloads into fewer servers and turning others off. However, services typically resist doing so, because of high response times during reactivation in handling traffic spikes. Moreover, services often want the memory and/or storage of all servers to be readily available at all times.

In this article, we propose a family of
barely alive
active low-power server states that facilitates both fast reactivation and access to memory while in a low-power state. We compare these states to previously proposed active and idle states. In particular, we investigate the impact of load bursts in each energy-saving scheme. We also evaluate the additional benefits of memory access under low-power states with a study of a search service using a cooperative main-memory cache. Finally, we propose a system that combines a barely-alive state with the off state. We find that the barely alive states can reduce service energy consumption by up to 38%, compared to an energy-oblivious system. We also find that these energy savings are consistent across a large parameter space.
Self-healing in unattended wireless sensor networks
Authors: Pietro Roberto Di , Ma Di , Soriente Claudio , Tsudik Gene
Published: November 2012

Wireless sensor networks (WSNs) appeal to a wide range of applications that involve the monitoring of various physical phenomena. However, WSNs are subject to many threats. In particular, lack of pervasive tamper-resistant hardware results in sensors being easy targets for compromise. Having compromised a sensor, the adversary learns all the sensor secrets, allowing it to later encrypt/decrypt or authenticate messages on behalf of that sensor. This threat is particularly relevant in the novel unattended wireless sensor networks (UWSNs) scenario. UWSNs operate without constant supervision by a trusted sink. UWSN's unattended nature and increased exposure to attacks prompts the need for special techniques geared towards regaining security after being compromised.

In this article, we investigate cooperative self-healing in UWSNs and propose various techniques to allow unattended sensors to recover security after compromise. Our techniques provide seamless healing rates even against a very agile and powerful adversary. The effectiveness and viability of our proposed techniques are assessed by thorough analysis and supported by simulation results. Finally, we introduce some real-world issues affecting UWSN deployment and provide some solutions for them as well as a few open problems calling for further investigation.