bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of oligotrophication on primary production in peri‐alpine lakes
Authors: Finger David , Wüest Alfred , Bossard Peter
Published: June 2013

During the second half of the 20th century untreated sewage released from housing and industry into natural waters led to a degradation of many freshwater lakes and reservoirs worldwide. In order to mitigate eutrophication, wastewater treatment plants, including Fe‐induced phosphorus precipitation, were implemented throughout the industrialized world, leading to reoligotrophication in many freshwater lakes. To understand and assess the effects of reoligotrophication on primary productivity, we analyzed 28 years of 14C assimilation rates, as well as other biotic and abiotic parameters, such as global radiation, nutrient concentrations and plankton densities in peri‐alpine Lake Lucerne, Switzerland. Using a simple productivity‐light relationship, we estimated continuous primary production and discussed the relation between productivity and observed limnological parameters. Furthermore, we assessed the uncertainty of our modeling approach based on monthly 14C assimilation measurements using Monte Carlo simulations. Results confirm that monthly sampling of productivity is sufficient for identifying long‐term trends in productivity and that conservation management has successfully improved water quality during the past three decades via reducing nutrients and primary production in the lake. However, even though nutrient concentrations have remained constant in recent years, annual primary production varies significantly from year to year. Despite the fact that nutrient concentrations have decreased by more than an order of magnitude, primary production has decreased only slightly. These results suggest that primary production correlates well to nutrients availability but meteorological conditions lead to interannual variability regardless of the trophic status of the lake. Accordingly, in oligotrophic freshwaters meteorological forcing may reduce productivity impacting on the entire food chain of the ecosystem.
Synthesis, Structures, and Luminescent Properties of two 3, 5‐Dimethyl‐1‐H‐1, 2,4‐triazole‐Based Zinc Metal‐Organic Frameworks with Aromatic Carboxylate as Coligand
Authors: Huang Yao , Liu Long‐Jiang , Zhou Ming‐Shan , Zhou Xiao‐Jun , Zhu Chao , Fu Fei‐E , Zhang Yong‐Ming
Published: June 2013

Two metal‐organic frameworks, [Zn(dmtrz)(btrc)1/3]n (1) and [Zn2(dmtrz)2(btec)(H2O)2]n (2) (dmtrz = 3, 5‐dimethyl‐1‐H‐1, 2,4‐triazole, btrc = 1, 3,5‐benzenetricarboxylate, btec = 1, 2,4, 5‐benzenetetracarboxylate), were synthesized by hydrothermal reaction. The crystal structure analysis reveals that compound 1 is a dense 3D framework with Schläfli symbols of {43}2{46·66·83}3, which is a loh1 structure. Compound 2 is a 2D network. In addition, the photoluminescence of two compounds were studied in solid state at room temperature, together with their thermal analysis.
Flavoured naturalness
Authors: Blanke Monika , Giudice Gian F. , Paradisi Paride , Perez Gilad , Zupan Jure
Published: June 2013

Abstract

We show that a large mixing between the right-handed charm and top squarks (i) is allowed by low-energy flavour constraints; (ii) reduces the experimental bound on the stop mass; (iii) has a mild, but beneficial, effect on fine-tuning; (iv) leads to interesting signatures at the LHC not presently investigated by experiments. We estimate the current bound on the stop mass, in presence of flavour mixing, and discuss the new collider signatures. The signal in the "Image missing" channel is large enough that it can be immediately searched for experimentally, while the signature with same-sign tops and "Image missing" requires a luminosity upgrade of the LHC.
Barriers to Accessing Surgical Care: A Cross‐Sectional Survey Conducted at a Tertiary Care Hospital in Karachi, Pakistan
Authors: Samad Lubna , Jawed Fayez , Sajun Sana Zehra , Arshad Mohammad Hussham , Baig‐Ansari Naila
Published: June 2013

Background

The need for surgical care far exceeds available facilities, especially in low income and poor countries. Limited data are available to help us understand the extent and nature of barriers that limit access to surgical care, particularly in the Asian subcontinent. The aim of this study was to understand factors that influence access to surgical care in a low‐income urban population.

Methods

An observational cross‐sectional study was conducted on 199 consecutive patients admitted for elective surgery from February to April 2010 to identify the presence and causes of delay in accessing surgical care.

Results

The median duration of symptoms were 7 and 4 months in women and men, respectively. The odds of delay between the onset of symptoms and seeking initial health care (first interval) is twice as likely for women than for men [52.7 vs. 37.5 %, odds ratio (OR) 1.9]. Lack of knowledge regarding treatment options [OR 3.8; 95 % confidence interval (CI) 1.4–10.3] and about disease implications (OR 2.4; 95 % CI 1.2–4.8) were cited most often. A second interval of delay (time from when surgery was first advised to the surgery) was reported by 123 (61.8 %) patients. Financial constraints (29.6 %) and environment‐related delays (10.6 %) were cited most often. More women than men thought there was a second delay interval (73 vs. 58 %). The odds of women having more co‐morbid conditions were nearly 4.7 times that of men (95 % CI 1.5–15.1).

Conclusions

A complex interaction of factors limits access to surgical care in developing countries. Women appear to face greater hurdles to accessing health care. Understanding local factors is essential to make care accessible.
Insulin receptor substrate‐1 (IRS‐1) forms a ribonucleoprotein complex associated with polysomes
Authors: Ozoe Atsufumi , Sone Meri , Fukushima Toshiaki , Kataoka Naoyuki , Arai Toshiya , Chida Kazuhiro , Asano Tomoichiro , Hakuno Fumihiko , Takahashi Shin-Ichiro
Published: June 2013

Insulin receptor substrates (IRSs) are known to play important roles in mediating intracellular insulin‐like growth factors (IGFs)/insulin signaling. In this study, we identified components of messenger ribonucleoprotein (mRNP) as IRS‐1‐associated proteins. IRS‐1 complex formation analysis revealed that IRS‐1 is incorporated into the complexes of molecular mass more than 1000 kDa, which were disrupted by treatment with RNase. Furthermore, oligo(dT) beads precipitated IRS‐1 from cell lysates, showing that the IRS‐1 complexes contained messenger RNA. Taken together with the data that IRS‐1 was fractionated into the polysome‐containing high‐density fractions, we concluded that IRS‐1 forms the novel complexes with mRNPs.
Resveratrol modulates ATPase activity of liposome‐reconstituted ABCG1
Authors: de Athayde Moncorvo Collado Alejandro , Corbalán Natalia , Homolya László , Morero Roberto , Minahk Carlos
Published: June 2013

ABCG1 is a half‐sized transporter with an unquestionable importance in cholesterol homeostasis. So far, its expression and thus its activity was suggested to be regulated at transcriptional level by LXR and PPAR agonists including polyphenols. However, it is unknown whether there are other mechanisms of up‐regulation of ABCG1 activity. In the present work resveratrol was shown to induce a nearly twofold increase in ATPase activity of reconstituted ABCG1. Evidence is presented for the first time suggesting that resveratrol is able to activate ABCG1 activity by an alternative mechanism that involves an indirect interaction.
Regulation of miR‐17‐92a cluster processing by the microRNA binding protein SND1
Authors: Heinrich Eva-Marie , Wagner Jasmin , Krüger Marcus , John David , Uchida Shizuka , Weigand Julia E. , Suess Beatrix , Dimmeler Stefanie
Published: June 2013

MicroRNAs are small non‐coding RNAs that regulate gene expression. Although all seven members of the miR‐17‐92a cluster originate from one primary transcript they are differentially expressed suggesting the presence of posttranscriptional regulation. By RNA pulldown and mass spectrometry we identified SND1, a known regulator of edited RNAs, interacting with pre‐miR‐92a and all mature miR‐17‐92a members. Hypoxic conditions lead to an elevation of the pri‐miR‐17‐92a transcript and significantly increased levels of the precursors whereas the mature miRs were not significantly changed. SND1 silencing resolved this block in processing and induced an increase in mature miRs. Together, SND1 might be the missing link between hypoxia and the differential regulation of miRNA processing.
ON A QUESTION OF HARTWIG AND LUH
Authors: DITTMER SAMUEL J. , KHURANA DINESH , NIELSEN PACE P.
Published: June 2013

In 1977 Hartwig and Luh asked whether an element $a$ in a Dedekind-finite ring $R$ satisfying $aR= {a}^{2} R$ also satisfies $Ra= R{a}^{2} $. In this paper, we answer this question in the negative. We also prove that if $a$ is an element of a Dedekind-finite exchange ring $R$ and $aR= {a}^{2} R$, then $Ra= R{a}^{2} $. This gives an easier proof of Dischinger’s theorem that left strongly $\pi $-regular rings are right strongly $\pi $-regular, when it is already known that $R$ is an exchange ring.
Modulational instability analysis of the cylindrical nonlinear von Neumann equation
Authors: FEDELE R. , MANNAN A. , TANJIA F. , DE NICOLA S. , JOVANOVIĆ D. , GIANFRANI L.
Published: June 2013

A theoretical investigation of both deterministic and statistical approaches to modulational instability arising in the cylindrical nonlinear von Neumann equation (CNLvNE) is carried out. This is done on the basis of a recently discovered exact mapping that relates the CNLvNE to the standard one. We show that the dispersion relations of the cylindrical case (for the examples considered here) do not depend explicitly on time and their functional forms do not change with respect to the corresponding standard cases. These results differ from the previous investigations.
Atypical interference effect of action observation in autism spectrum conditions
Authors: Cook J. , Swapp D. , Pan X. , Bianchi-Berthouze N. , Blakemore S-J.
Published: June 2013

Background

Observing incongruent actions interferes with ongoing action execution. This ‘interference effect’ is larger for observed biological actions than for non-biological actions. The current study used virtual reality to investigate the biological specificity of interference effects of action observation in autism spectrum conditions (ASC).

Method

High-functioning adults with ASC and age- and IQ-matched healthy controls performed horizontal sinusoidal arm movements whilst observing arm movements conducted by a virtual reality agent with either human or robot form, which moved with either biological motion or at a constant velocity. In another condition, participants made the same arm movements while observing a real human. Observed arm movements were either congruent or incongruent with executed arm movements. An interference effect was calculated as the average variance in the incongruent action dimension during observation of incongruent compared with congruent movements.

Results

Control participants exhibited an interference effect when observing real human and virtual human agent incongruent movements but not when observing virtual robot agent movements. Individuals with ASC differed from controls in that they showed no interference effects for real human, virtual human or virtual robot movements.

Conclusions

The current study demonstrates atypical interference effects in ASC.
Incidence ofChlamydia trachomatisinfection in women in England: two methods of estimation
Authors: PRICE M. J. , ADES A. E. , DE ANGELIS D. , WELTON N. J. , MACLEOD J. , TURNER K. , HORNER P. J.
Published: June 2013

Information on the incidence ofChlamydia trachomatis(CT) is essential for models of the effectiveness and cost-effectiveness of screening programmes. We developed two independent estimates of CT incidence in women in England: one based on an incidence study, with estimates ‘recalibrated’ to the general population using data on setting-specific relative risks, and allowing for clearance and re-infection during follow-up; the second based on UK prevalence data, and information on the duration of CT infection. The consistency of independent sources of data on incidence, prevalence and duration, validates estimates of these parameters. Pooled estimates of the annual incidence rate in women aged 16–24 and 16–44 years for 2001–2005 using all these data were 0·05 [95% credible interval (CrI) 0·035–0·071] and 0·021 (95% CrI 0·015–0·028), respectively. Although, the estimates apply to England, similar methods could be used in other countries. The methods could be extended to dynamic models to synthesize, and assess the consistency of data on contact and transmission rates.
Neuroanatomical Correlates of Executive Functions: A Neuropsychological Approach Using the EXAMINER Battery
Authors: Robinson Heather , Calamia Matthew , Gläscher Jan , Bruss Joel , Tranel Daniel
Published: June 2013

Executive functions (EF) encompass a variety of higher-order capacities such as judgment, planning, decision-making, response monitoring, insight, and self-regulation. Measuring such abilities quantitatively and establishing their neural correlates has proven to be challenging. Here, using a lesion-deficit approach, we report the neural correlates of a variety of EF tests that were developed under the auspices of the NINDS-supported EXAMINER project (Kramer, 2011;www.examiner.ucsf.edu). We administered a diverse set of EF tasks that tap three general domains—cognitive, social/emotional, and insight—to 37 patients with focal lesions to the frontal lobes, and 25 patients with lesions outside the frontal lobes. Using voxel-based lesion-symptom mapping (VLSM), we found that damage to the ventromedial prefrontal cortex (vmPFC) was predominately associated with deficits in social/emotional aspects of EF, while damage to dorsolateral prefrontal cortex (dlPFC) and anterior cingulate was predominately associated with deficits in cognitive aspects of EF. Evidence for an important role of some non-frontal regions (e.g., the temporal poles) in some aspects of EF was also found. The results provide further evidence for the neural basis of EF, and extend previous findings of the dissociation between the roles of the ventromedial and dorsolateral prefrontal sectors in organizing, implementing, and monitoring goal-directed behavior. (JINS, 2013,19, 1–12)
Towards healthy and sustainable food consumption: an Australian case study
Authors: Friel Sharon , Barosh Laurel J , Lawrence Mark
Published: June 2013

Objective

To articulate a healthy and sustainable (H&S) diet; outline key health and environmental sustainability principles that can be applied in the selection of foods for inclusion in such a diet; and describe a methodology with which to assess the availability and affordability of a H&S food basket.

Design

We synthesized publically available evidence on the environmental impact of different foods from academic, government, industry and non-government sources and constructed a hypothetical H&S equivalent of the typical Australian diet. Based on this, we constructed a weekly H&S food basket for a household of two adults and two children.

Setting

Australia.

Subjects

Australian populations.

Results

The H&S diet is based on three overarching principles: (i) any food that is consumed above a person's energy requirement represents an avoidable environmental burden in the form of greenhouse gas emissions, use of natural resources and pressure on biodiversity; (ii) reducing the consumption of discretionary food choices, which are energy-dense and highly processed and packaged, reduces both the risk of dietary imbalances and the use of environmental resources; and (iii) a diet comprising less animal- and more plant-derived foods delivers both health and ecological benefits.

Conclusions

We have focused on the articulation of a H&S diet not to facilitate ‘policy drift’ to focus on individual dietary choice, but rather to provide evidence to extend dietary guideline recommendations so as to integrate environmental considerations within the scope of food and health policy advice in Australia and elsewhere.
Training oncology and palliative care clinical nurse specialists in psychological skills: Evaluation of a pilot study
Authors: Clark Jane E. , Aitken Susan , Watson Nina , McVey Joanne , Helbert Jan , Wraith Anita , Taylor Vanessa , Catesby Sarah
Published: June 2013

Objective:

National guidelines in the United Kingdom recommend training Clinical Nurse Specialists in psychological skills to improve the assessment and intervention with psychological problems experienced by people with a cancer diagnosis (National Institute for Health and Clinical Excellence, 2004). This pilot study evaluated a three-day training program combined with supervision sessions from Clinical Psychologists that focused on developing skills in psychological assessment and intervention for common problems experienced by people with cancer.

Methods:

Questionnaires were developed to measure participants’ levels of confidence in 15 competencies of psychological skills. Participants completed these prior to the program and on completion of the program. Summative evaluation was undertaken and results were compared. In addition, a focus group interview provided qualitative data of participants’ experiences of the structure, process, and outcomes of the program.

Results:

Following the program, participants rated their confidence in psychological assessment and skills associated with providing psychological support as having increased in all areas. This included improved knowledge of psychological theories, skills in assessment and intervention and accessing and using supervision appropriately. The largest increase was in providing psycho-education to support the coping strategies of patients and carers. Thematic analysis of interview data identified two main themes including learning experiences and program enhancements. The significance of the clinical supervision sessions as key learning opportunities, achieved through the development of a community of practice, emerged.

Significance of results:

Although this pilot study has limitations, the results suggest that a combined teaching and supervision program is effective in improving Clinical Nurse Specialists’ confidence level in specific psychological skills. Participants’ experiences highlighted suggestions for refinement and development of the program. Opportunities for further research and developments in this area are discussed.
Development of Body Mass Index of Japanese Triplets From Birth Until the Onset of Puberty
Authors: Yokoyama Yoshie , Pitkäniemi Janne , Kaprio Jaakko , Silventoinen Karri
Published: June 2013

We aimed to analyze the characteristics of development of relative weight in Japanese triplets from birth until 12 years of age. Data were collected through a mailed questionnaire sent to mothers of triplets asking for information recorded in medical records. Altogether we had information on 1,061 triplet children of 354 mothers born between 1978 and 2006. For these births, data on triplets’ height and weight growth, gestational age, sex, parity, and maternal age at delivery were obtained from records in the maternal and child health handbooks and records from the schools where children receive health check-ups. In addition, information on maternal height and weight was obtained. Triplets have a lower ponderal index at birth and lower body mass index (BMI) compared with the general population until 12 years of age, except for the period during 1 and 3 years of age. Moreover, birth weight had the strongest contribution to BMI of triplets until 6 years of age. After 9 years of age, maternal BMI was a significant factor affecting BMI of triplets.
FilGAP and its close relatives: a mediator of Rho–Rac antagonism that regulates cell morphology and migration
Authors: Nakamura Fumihiko
Published: June 2013

Cell migration, phagocytosis and cytokinesis are mechanically intensive cellular processes that are mediated by the dynamic assembly and contractility of the actin cytoskeleton. GAPs (GTPase-activating proteins) control activities of the Rho family proteins including Cdc42, Rac1 and RhoA, which are prominent upstream regulators of the actin cytoskeleton. The present review concerns a class of Rho GAPs, FilGAP (ARHGAP24 gene product) and its close relatives (ARHGAP22 and AHRGAP25 gene products). FilGAP is a GAP for Rac1 and a binding partner of FLNa (filamin A), a widely expressed F-actin (filamentous actin)-cross-linking protein that binds many different proteins that are important in cell regulation. Phosphorylation of FilGAP serine/threonine residues and binding to FLNa modulate FilGAP's GAP activity and, as a result, its ability to regulate cell protrusion and spreading. FLNa binds to FilGAP at F-actin-enriched sites, such as at the leading edge of the cell where Rac1 activity is controlled to inhibit actin assembly. FilGAP then dissociates from FLNa in actin networks by myosin-dependent mechanical deformation of FLNa's FilGAP-binding site to relocate at the plasma membrane by binding to polyphosphoinositides. Since actomyosin contraction is activated downstream of RhoA–ROCK (Rho-kinase), RhoA activity regulates Rac1 through FilGAP by signalling to the force-generating system. FilGAP and the ARHGAP22 gene product also act as mediators between RhoA and Rac1 pathways, which lead to amoeboid and mesenchymal modes of cell movements respectively. Therefore FilGAP and its close relatives are key regulators that promote the reciprocal inhibitory relationship between RhoA and Rac1 in cell shape changes and the mesenchymal–amoeboid transition in tumour cells.
N-terminal tagging of two-pore channels interferes with NAADP action
Authors: Guse Andreas H.
Published: June 2013

NAADP (nicotinic acid–adenine dinucleotide phosphate) is the most potent Ca2+-releasing second messenger known to date. Since its discovery in 1995 identifying the NAADP receptor protein/Ca2+ channel has been a major persuit of the Ca2+ signalling community. In their paper ‘The N-terminal region of two-pore channel 1 regulates trafficking and activation by NAADP’ published in this issue of the Biochemical Journal Patel and colleagues describe that the N-terminus of one of the NAADP receptor protein/Ca2+ channel candidates, TPC1 (two-pore channel 1), is crucial for protein targeting and for sensitivity to NAADP.
Fluorescence enhancement mechanism in phosphor CaAl12O19:Mn4 + modified with alkali‐chloride
Authors: Li Yanan , Xiao Zunhong , Xu Lizhi , Zou Yingping , Guo Mingchun
Published: June 2013

CaMAl12 − xO19:x Mn4 + (M is one or more of K+, Na+, Li+) materials were prepared by a combustion method in air atmosphere. The Mn concentration, the influence of one or more alkali‐chloride on luminescence properties, crystal phases and surface morphology of the samples were investigated. The fluorescence intensity of CaAl11.98O19:0.02Mn4 + modified by combining three kinds of alkali‐chloride can be enhanced by three times. Blue shift of CaMAl12 − xO19:x Mn4 + luminescence is explained from the point of view of enhancing electron cloud deformation after doping. Alkali metal ions were beneficial to form hexagonal CaAl12O19 while there was certain inhibition to other peak strengths. The mechanism is the coexistence of alkali‐chloride replacing Al3 + or Ca2 + instead of Mn2 + based on the difference of cation radius, this would increase the luminous centre of Mn4 + and provide charge compensation at the same time. The size of red phosphors was 5–10 μm, which is useful for light emitting diode applications.
Vibration response of an atomic force microscopy piezoelectrically actuated microcantilever in liquid environment
Authors: Korayem M. H. , Ghaderi R.
Published: June 2013

Piezoelectric microcantilevers (MCs) are a new generation of atomic force microscopy (AFM) beams. They are capable of imaging at a high speed and consuming low energy. These MCs are also built commercially, with non‐uniform geometry; and they can be utilised in different environments (gases and liquid). The objective of this Letter is to investigate the vibration behaviour of these types of MCs in liquid. The modelling of the MCs' vibrating motion has been carried out by using the non‐uniform beam model, and also by the proposed lumped mass model consisting of three spheres. The obtained results of these two models are compared with each other and with the experimental results. In addition, the effects of liquid mechanical properties, the distance of the MC to the sample surface and also the MC inclined angle at higher fundamental modes are investigated. Sensitivity analysis was performed through the Sobol method to study the effect of the MCs' geometrical dimensions on Reynolds number. Such information can be used to choose appropriate parameters to apply an AFM piezoelectric MC in a liquid environment.
Nanoencapsulation of Hypericum perforatum and doxorubicin anticancer agents in PLGA nanoparticles through double emulsion technique
Authors: Amjadi I. , Rabiee M. , Hosseini M.S. , Sefidkon F. , Mozafari M.
Published: June 2013

A comparative study is performed on Hypericum perforatum (H. perforatum) and doxorubicin (Dox) anticancer agents. Double emulsion and sonication techniques were used to enhance drug loading efficiency in poly(lactic‐co‐glycolic acid) (PLGA) nanoparticles (NPs). To distinguish the efficiency of the double emulsion method, drug entrapment efficiency was measured. In vitro release studies were carried out to evaluate drug release profiles. Entrapment efficiency was estimated to be 48 and 21% for Dox‐loaded and H. perforatum ‐loaded NPs, respectively. Surprisingly, the encapsulation process disrupted the formation of Dox crystals (Dox in NPs converted from the crystalline to the amorphous phase), whereas disordered crystalline was observed for H. perforatum. In vitro release studies suggested that the total released drug was about 71% of the whole entrapped drug after 20 days. MTT assay confirmed that Dox was more toxic than H. perforatum. This study revealed that H. perforatum is a good choice for further experiments in drug delivery systems because of low cardiotoxicity according to the herbaceous nature of this anticancer agent.
Classical line shapes based on analytical solutions of bimolecular trajectories in collision induced emission. II. Reactive collisions
Authors: Reguera David , Rawlings Philip K. , Birnbaum George
Published: June 2013

The classical theory of collision induced emission (CIE) from pairs of dissimilar rare gas atoms was developed in Paper I [D. Reguera and G. Birnbaum, J. Chem. Phys. 125, 184304 (2006)]10.1063/1.2371097 from a knowledge of the straight line collision trajectory and the assumption that the magnitude of the dipole could be represented by an exponential function of the inter-nuclear distance. This theory is extended here to deal with other functional forms of the induced dipole as revealed by ab initio calculations. Accurate analytical expression for the CIE can be obtained by least square fitting of the ab initio values of the dipole as a function of inter-atomic separation using a sum of exponentials and then proceeding as in Paper I. However, we also show how the multi-exponential fit can be replaced by a simpler fit using only two analytic functions. Our analysis is applied to the polar molecules HF and HBr. Unlike the rare gas atoms considered previously, these atomic pairs form stable bound diatomic molecules. We show that, interestingly, the spectra of these reactive molecules are characterized by the presence of multiple peaks. We also discuss the CIE arising from half collisions in excited electronic states, which in principle could be probed in photo-dissociation experiments.
Symmetry analysis of wave equation on static spherically symmetric spacetimes with higher symmetries
Authors: Azad H. , Al-Dweik Ahmad Y. , Ghanam R. , Mustafa M. T.
Published: June 2013

Symmetry analysis of wave equation on all static spherically symmetric spacetimes admitting maximal isometry groups G10 or G7 or G6 is carried out. Symmetry algebras of the wave equation are found and their structural information-in the sense of Iwasawa decomposition-is obtained. Joint invariants of appropriate subalgebras are utilized to obtain many exact solutions of the wave equation on static spherically symmetric spacetimes.
Electron and hole deep levels related to Sb-mediated Ge quantum dots embedded in n-type Si, studied by deep level transient spectroscopy
Authors: Rangel-Kuoppa Victor-Tapio , Tonkikh Alexander , Werner Peter , Jantsch Wolfgang
Published: June 2013

The deep level transient spectroscopy technique is used on a Ti Schottky diode on n-Si with embedded Ge quantum dots (QDs) obtained by Sb-mediated growth. We discover an electron trap and two hole traps within the Si band gap at the plane of the Ge QDs. The electron trap has an activation energy of 87 ± 7 meV. One hole trap has an activation energy of 304 ± 32 meV, The second hole trap is represented by an energy sub-band between 125 and 250 meV above the top of the Si valence band. The electron level (87 ± 7 meV) and the hole energy sub-band (125–250 meV) are identified as energy levels of the Ge QDs array. The deepest trap level for holes (304 meV) has not been identified yet.
Ultrasound generation and high-frequency motion of magnetic nanoparticles in an alternating magnetic field: Toward intracellular ultrasound therapy?
Authors: Carrey J. , Connord V. , Respaud M.
Published: June 2013

We show theoretically that, in an inhomogeneous alternating magnetic field of frequency f, due to the alternating gradient, magnetic nanoparticles oscillate mechanically and generate ultrasound waves. This effect is maximized and better controlled if a static magnetic field is superimposed to an alternating gradient. It makes possible the generation of ultrasounds intracellularly and might also explain recent experiments in magnetic hyperthermia in which cells have been killed without any global temperature increase. Combined to an efficient targeting, it could permit ultrasound therapy with an unprecedented spatial resolution.
Origins of magnetic damping measurement variations using ferromagnetic resonance for nano-sized devices
Authors: Eason Kwaku , Patricia Rouelli Garcia Sabino Maria , Tran Michael , Fook Liew Yun
Published: June 2013

It is shown that ferromagnetic resonance measured in larger thin films yield varying results for damping in nanosized devices. Results are shown to critically depend on magnetic parameters, scalar and vector. Results here also explain why different experiments have concluded different size-dependent trends measuring damping with in-plane devices. The observed variation is due, in part, to a crossover in the dominant eigen-mode and unique eigen-mode evolution. However, antithesizing in-plane devices, we find that for out-of-plane magnetization, distinct symmetric eigen-modes demonstrates ideal stability, leading to no variation in apparent damping, suggesting a better measurement configuration using larger samples.
Exchange bias effect in the martensitic state of Ni-Co-Mn-Sn film
Authors: Machavarapu Ramudu , Jakob Gerhard
Published: June 2013

We report a relatively large exchange bias (EB) effect in epitaxially grown Ni-Co-Mn-Sn film. EB effect has been observed at low temperature below 60 K with a maximum EB field of 139 Oe at 5 K which is high compared to Ni-Mn-Sn thin films. Systematic studies on the magnetic properties show that both EB field and coercivity decreased with increase in temperature. Martensitic transformation at room temperature was confirmed from the atomic force microscopy micrograph exhibiting twin pattern. The observed EB behavior in Ni45.0Co4.4Mn41.5Sn9.1 film is attributed to the coexistence of antiferromagnetic and ferromagnetic exchange interactions in the system.
Physisorption-induced electron scattering on the surface of carbon-metal core-shell nanowire arrays for hydrogen sensing
Authors: Yick S. , Yajadda M. M. A. , Bendavid A. , Han Z. J. , Ostrikov K.
Published: June 2013

Palladium is sputtered on multi-walled carbon nanotube forests to form carbon-metal core-shell nanowire arrays. These hybrid nanostructures exhibited resistive responses when exposed to hydrogen with an excellent baseline recovery at room temperature. The magnitude of the response is shown to be tuneable by an applied voltage. Unlike the charge-transfer mechanism commonly attributed to Pd nanoparticle-decorated carbon nanotubes, this demonstrates that the hydrogen response mechanism of the multi-walled carbon nanotube-Pd core-shell nanostructure is due to the increase in electron scattering induced by physisorption of hydrogen. These hybrid core-shell nanostructures are promising for gas detection in hydrogen storage applications.
Femtosecond laser-induced microstructures on diamond for microfluidic sensing device applications
Authors: Su Shi , Li Jiangling , Lee Graham C. B. , Sugden Kate , Webb David , Ye Haitao
Published: June 2013

This paper reported a three-dimensional microfluidic channel structure, which was fabricated by Yb:YAG 1026 nm femtosecond laser irradiation on a single-crystalline diamond substrate. The femtosecond laser irradiation energy level was optimized at 100 kHz repetition rate with a sub-500 femtosecond pulse duration. The morphology and topography of the microfluidic channel were characterized by a scanning electron microscope and an atomic force microscope. Raman spectroscopy indicated that the irradiated area was covered by graphitic materials. By comparing the cross-sectional profiles before/after removing the graphitic materials, it could be deduced that the microfluidic channel has an average depth of ∼410 nm with periodical ripples perpendicular to the irradiation direction. This work proves the feasibility of using ultra-fast laser inscription technology to fabricate microfluidic channels on biocompatible diamond substrates, which offers a great potential for biomedical sensing applications.
Local structure around rare-earth ions in B2O3 glass at high pressure
Authors: Funabiki Fuji , Matsuishi Satoru , Hosono Hideo
Published: June 2013

Melt quenching of B2O3 with less than 25 mol. % rare-earth oxide (RE2O3) at ambient pressure results in a milky white glass because of liquid-liquid phase separation into B2O3 and RE2O3·3B2O phases. In contrast, we have found that melt quenching under GPa-order pressure realizes a transparent RE-doped B2O3 glass. This study investigates the local structure around the RE ions in the B2O3 glass prepared at 3 GPa using optical measurements and electron-spin-echo envelope modulation spectroscopy. It is shown that the RE-rich microparticles disappear and the RE ions are isolated from each other in a highly symmetric crystal field formed by triangular and tetrahedral boron units. This result is consistent with that extrapolated from the data for RE-doped sodium borate glasses.
Improved cation valence state in molybdenum oxides by ultraviolet-ozone treatments and its applications in organic light-emitting diodes
Authors: Shi Xiao-Bo , Xu Mei-Feng , Zhou Dong-Ying , Wang Zhao-Kui , Liao Liang-Sheng
Published: June 2013

The authors demonstrate a thick MoO3 layer (60 nm) as a good short reduction layer in organic light emitting diodes (OLEDs), which is especially useful for large-area and flexible OLEDs to prevent short circuit issues. The crystallization of organic material and the increase of driving voltage induced by a thick MoO3 layer in OLEDs were resolved by a simple ultraviolet-ozone (UV-ozone) treatment. Ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, contact angle, and atomic force microscope analyses revealed that a longer UV-ozone treatment resulted in an optimized fraction of oxygen vacancies in MoO3, which is responsible for the improved device performance.
Designed azurins show lower reorganization free energies for intraprotein electron transfer
Authors: Farver Ole , Marshall Nicholas M. , Wherland Scot , Lu Yi , Pecht Israel
Published: June 2013

Low reorganization free energies are necessary for fast electron transfer (ET) reactions. Hence, rational design of redox proteins with lower reorganization free energies has been a long-standing challenge, promising to yield a deeper understanding of the underlying principles of ET reactivity and to enable potential applications in different energy conversion systems. Herein we report studies of the intramolecular ET from pulse radiolytically produced disulfide radicals to Cu(II) in rationally designed azurin mutants. In these mutants, the copper coordination sphere has been fine-tuned to span a wide range of reduction potentials while leaving the metal binding site effectively undisrupted. We find that the reorganization free energies of ET within the mutants are indeed lower than that of WT azurin, increasing the intramolecular ET rate constants almost 10-fold: changes that are correlated with increased flexibility of their copper sites. Moreover, the lower reorganization free energy results in the ET rate constants reaching a maximum value at higher driving forces, as predicted by the Marcus theory.
Chimera states in mechanical oscillator networks
Authors: Martens Erik Andreas , Thutupalli Shashi , Fourrière Antoine , Hallatschek Oskar
Published: June 2013

The synchronization of coupled oscillators is a fascinating manifestation of self-organization that nature uses to orchestrate essential processes of life, such as the beating of the heart. Although it was long thought that synchrony and disorder were mutually exclusive steady states for a network of identical oscillators, numerous theoretical studies in recent years have revealed the intriguing possibility of “chimera states,” in which the symmetry of the oscillator population is broken into a synchronous part and an asynchronous part. However, a striking lack of empirical evidence raises the question of whether chimeras are indeed characteristic of natural systems. This calls for a palpable realization of chimera states without any fine-tuning, from which physical mechanisms underlying their emergence can be uncovered. Here, we devise a simple experiment with mechanical oscillators coupled in a hierarchical network to show that chimeras emerge naturally from a competition between two antagonistic synchronization patterns. We identify a wide spectrum of complex states, encompassing and extending the set of previously described chimeras. Our mathematical model shows that the self-organization observed in our experiments is controlled by elementary dynamical equations from mechanics that are ubiquitous in many natural and technological systems. The symmetry-breaking mechanism revealed by our experiments may thus be prevalent in systems exhibiting collective behavior, such as power grids, optomechanical crystals, or cells communicating via quorum sensing in microbial populations.
The yeast dynein Dyn2-Pac11 complex is a dynein dimerization/processivity factor: structural and single-molecule characterization
Authors: Rao Lu , Romes Erin M. , Nicholas Matthew P. , Brenner Sibylle , Tripathy Ashutosh , Gennerich Arne , Slep Kevin C.
Published: June 2013

Cytoplasmic dynein is the major microtubule minus end–directed motor. Although studies have probed the mechanism of the C-terminal motor domain, if and how dynein's N-terminal tail and the accessory chains it binds regulate motor activity remain to be determined. Here, we investigate the structure and function of the Saccharomyces cerevisiae dynein light (Dyn2) and intermediate (Pac11) chains in dynein heavy chain (Dyn1) movement. We present the crystal structure of a Dyn2-Pac11 complex, showing Dyn2-mediated Pac11 dimerization. To determine the molecular effects of Dyn2 and Pac11 on Dyn1 function, we generated dyn2Δ and dyn2Δpac11Δ strains and analyzed Dyn1 single-molecule motor activity. We find that the Dyn2-Pac11 complex promotes Dyn1 homodimerization and potentiates processivity. The absence of Dyn2 and Pac11 yields motors with decreased velocity, dramatically reduced processivity, increased monomerization, aggregation, and immobility as determined by single-molecule measurements. Deleting dyn2 significantly reduces Pac11-Dyn1 complex formation, yielding Dyn1 motors with activity similar to Dyn1 from the dyn2Δpac11Δ strain. Of interest, motor phenotypes resulting from Dyn2-Pac11 complex depletion bear similarity to a point mutation in the mammalian dynein N-terminal tail (Loa), highlighting this region as a conserved, regulatory motor element.
Stacked reverberation mapping
Authors: Fine S. , Shanks T. , Green P. , Kelly B. C. , Croom S. M. , Webster R. L. , Berger E. , Chornock R. , Burgett W. S. , Chambers K. C. , Kaiser N. , Price P. A.
Published: June 2013

Over the past 20 years reverberation mapping has proved one of the most successful techniques for studying the local (<1 pc) environment of supermassive black holes that drive active galactic nuclei. Key successes of reverberation mapping have been direct black hole mass estimates, the radius–luminosity relation for the Hβ line and the calibration of single-epoch mass estimators commonly employed up to z ∼ 7. However, observing constraints mean that few studies have been successful at z > 0.1, or for the more-luminous quasars that make up the majority of current spectroscopic samples, or for rest-frame ultraviolet emission lines available in optical spectra of z > 0.5 objects. Previously, we described a technique for stacking cross-correlations to obtain reverberation mapping results at high z. Here, we present the first results from a campaign designed for this purpose. We construct stacked cross-correlation functions for the C iv and Mg ii lines and find a clear peak in both. We find that the peak in the Mg ii correlation is at longer lags than C iv consistent with previous results at low redshift. For the C iv sample, we are able to bin by luminosity and find evidence for increasing lags for more-luminous objects. This C iv radius–luminosity relation is consistent with previous studies but with a fraction of the observational cost.
Targeted mutations in a highly conserved motif of the nsp1β protein impair the interferon antagonizing activity of porcine reproductive and respiratory syndrome virus
Authors: Li Yanhua , Zhu Longchao , Lawson Steven R. , Fang Ying
Published: June 2013

Non-structural protein 1β (nsp1β) of porcine reproductive and respiratory syndrome virus (PRRSV) contains a papain-like cysteine protease (PLPβ) domain and has been identified as the main viral protein antagonizing the host innate immune response. In this study, nsp1β was determined to suppress the expression of reporter genes as well as to suppress ‘self-expression’ in transfected cells, and this activity appeared to be associated with its interferon (IFN) antagonist function. To knock down the effect of nsp1β on IFN activity, a panel of site-specific mutations in nsp1β was analysed. Double mutations K130A/R134A (type 1 PRRSV) or K124A/R128A (type 2 PRRSV) targeting a highly conserved motif of nsp1β, GKYLQRRLQ (in bold), impaired the ability of nsp1β to suppress IFN-β and reporter gene expression, as well as to suppress ‘self-expression’ in vitro. Subsequently, viable recombinant viruses vSD01-08-K130A/R134A and vSD95-21-K124A/R128A, containing double mutations in the GKYLQRRLQ motif were generated using reverse genetics. In comparison with WT viruses, these nsp1β mutants showed impaired growth ability in infected cells, but the PLPβ cleavage function was not directly affected. The expression of selected innate immune genes was determined in vSD95-21-K124A/R128A mutant-infected cells. The results consistently showed that gene expression levels of IFN-α, IFN-β and IFN-stimulated gene 15 were upregulated in cells that were infected with the vSD95-21-K124A/R128A compared with that of WT virus. These data suggest that PRRSV nsp1β may selectively suppress cellular gene expression, including expression of genes involved in the host innate immune function. Modifying the key residues in the highly conserved GKYLQRRLQ motif could attenuate virus growth and improve the cellular innate immune responses.
Genomic analysis of coxsackieviruses A1, A19, A22, enteroviruses 113 and 104: viruses representing two clades with distinct tropism within enterovirus C
Authors: Tokarz Rafal , Haq Saddef , Sameroff Stephen , Howie Stephen R. C. , Lipkin W. Ian
Published: June 2013

Coxsackieviruses (CV) A1, CV-A19 and CV-A22 have historically comprised a distinct phylogenetic clade withinEnterovirus(EV)C. Several novel serotypes that are genetically similar to these three viruses have been recently discovered and characterized. Here, we report the coding sequence analysis of two genotypes of a previously uncharacterized serotype EV-C113 from Bangladesh and demonstrate that it is most similar to CV-A22 and EV-C116 within the capsid region. We sequenced novel genotypes of CV-A1, CV-A19 and CV-A22 from Bangladesh and observed a high rate of recombination within this group. We also report genomic analysis of the rarely reported EV-C104 circulating in the Gambia in 2009. All available EV-C104 sequences displayed a high degree of similarity within the structural genes but formed two clusters within the non-structural genes. One cluster included the recently reported EV-C117, suggesting an ancestral recombination between these two serotypes. Phylogenetic analysis of all available complete genome sequences indicated the existence of two subgroups within this distinctEnterovirus Cclade: one has been exclusively recovered from gastrointestinal samples, while the other cluster has been implicated in respiratory disease.
Libraries and student persistence at southern colleges and universities
Authors: Teske Boris , DiCarlo Michael , Cahoy Dexter
Published: June 2013

Purpose

The aim of this paper is to determine whether or how academic libraries affect student achievement.

Design/methodology/approach

The paper uses computation of Pearson's r coefficients and predictor values for correlations of academic library statistics with first‐year retention and six‐year graduation rates reported to the Integrated Postsecondary Education Data System by Southern Regional Education Board four‐year colleges and universities in 2010.

Findings

Book collection size in doctoral university libraries has the strongest correlation with retention and graduation rates, in the sample, and predicts for every 10 percent increase a 0.5 percent improvement in retention and a 0.7 percent higher graduation rate.

Originality/value

The paper documents the first impact study to correlate library statistics with both retention and graduation rates from a large sample of doctoral, Masters' and bachelors' degree‐conferring institutions. It calculates 21 predictor values of interest to academic administrators.
Academic library participation in recruitment and retention initiatives
Authors: Hubbard Melissa A. , Loos Amber T.
Published: June 2013

Purpose

The purpose of this study is to determine the extent to which academic libraries participate in and assess initiatives to increase or maintain student enrollment levels at colleges and universities in the US.

Design/methodology/approach

An online survey of academic library directors in the US was conducted. The 31 question survey was distributed via email to 321 librarians in the sample population. The survey response rate was 42.7 percent. Quantitative data were analyzed using SPSS 19.0 and qualitative data were coded according to recruitment or retention strategy.

Findings

Regardless of institution type or size, libraries in the sample population were just as likely to participate in recruitment and retention initiatives. However, some libraries stood out as particularly active in recruitment and retention initiatives. Indicators of active library participation were identified.

Research limitations/implications

The response rate for the survey did not generate a statistically significant sample size, given the population. However, the data generated here contribute significantly to the relatively scant literature on academic library participation in retention and recruitment activities. The findings also suggest the need for the profession to focus on creating assessment tools to measure library impact on recruitment and retention.

Originality/value

No other studies have surveyed the academic library field to document the extent to which they participate in and assess recruitment and retention initiatives.