bluuebunny/crossref_metadata_2025 huggingface dataset:
Joint-level mechanics of the walk-to-run transition in humans
Authors: Pires Neville J. , Lay Brendan S. , Rubenson Jonas
Published: August 2014

Two commonly proposed mechanical explanations for the WRT include the prevention of muscular over-exertion (effort) and the minimisation of peak musculoskeletal loads and thus injury risk. The purpose of this study was to address these hypotheses at a joint level by analysing the effect of speed on discrete lower-limb joint kinetic parameters in humans across a wide range of walking and running speeds including walking above and running below the WRT speed. Joint work, peak instantaneous joint power, and peak joint moments in the sagittal and frontal plane of the ankle, knee and hip from 8 participants were collected for 10 walking speeds (30–120% of their WRT) and 10 running speeds (80–170% of their WRT) on a force-plate instrumented treadmill. Of the parameters analysed, three satisfied our statistical criteria of the ‘effort-load’ hypothesis of the WRT. Mechanical parameters that provide an acute signal (peak moment and peak power) were more strongly associated with the gait transition than parameters that reflect the mechanical function across a portion of the stride. We found that both the ankle (peak instantaneous joint power during swing) and hip mechanics (peak instantaneous joint power and peak joint moments in stance) can influence the transition from walking to running in human locomotion and may represent a cascade of mechanical events beginning at the ankle and leading to an unfavourable compensation at the hip. Both the ankle and hip mechanisms may contribute to gait transition by lowering the muscular effort of running compared to walking at the WRT speed. Although few of the examined joint variables satisfied our hypothesis of the WRT, most showed a general marked increase when switching from walking to running across all speeds where both walking and running are possible, highlighting the fundamental differences in the mechanics of walking and running. While not eliciting the WRT per se, these variables may initiate the transition between stable walking and running patterns. Those variables that were invariant of gait were predominantly found in the swing phase.
Early deactivation of slower muscle fibres at high movement frequencies
Authors: Blake Ollie M. , Wakeling James M.
Published: August 2014

Animals produce rapid movements using fast cyclical muscle contractions. These types of movements are better suited to faster muscle fibres within muscles of mixed fibre types as they can shorten at faster velocities and achieve higher activation-deactivation rates than their slower counterparts. Preferential recruitment of faster muscle fibres has previously been shown during high velocity contractions. Additionally, muscle deactivation takes longer than activation and therefore may pose a limitation to fast cyclical contractions. It has been speculated that slower fibres maybe deactivated before faster fibres to accommodate their longer deactivation time. This study aimed to test whether shifts in muscle fibre recruitment occur with derecruitment of slow fibres before the faster fibres at high cycle frequencies. Electromyographic (EMG) signals were collected from the medial gastrocnemius at an extreme range of cycle frequencies and workloads. Wavelets were used to resolve the EMG signals into time and frequency space and the primary sources of variability within the EMG frequency spectra were identified through principal component analysis. A general early derecruitment of slower fibres was evident at the end of muscle excitation for the higher cycle frequencies, and additional slower fibre recruitment was present at the highest cycle frequency. The duration of muscle excitation reached a minimum of about 150 ms and did not change for the three highest cycle frequencies suggesting a duration limit for the medial gastrocnemius. This study provides further evidence of modifications of muscle fibre recruitment strategies to meet the mechanical demands of movement.
Complementary therapies: education for community practice
Authors: Stevensen Caroline
Published: August 2014

Complementary therapy education is in a state of rapid growth and development. Courses in a wide variety of therapies abound, offering different levels of qualifications and academic accreditation. It is very much the responsibility of the individual professional wishing to train in complementary therapies to sort through the maze of educational organisations and establishments. There are, at present, no specialist courses in complementary therapies for community health nurses. It is considered important to have introduced generalist training before specialism is embarked upon.

This paper addresses a number of professional issues. These include course validation, continuing education, clinical supervision and professional indemnity insurance.
Combined phototherapy/low intensity laser on venous ulceration
Authors: Ashford RL , Brown NP , Nolan C , Lenton B , Howell C
Published: August 2014

Some venous ulcers of the lower limb can prove to be extremely difficult to manage. The use of low intensity laser therapy is being used as an adjunct treatment modality in ulcer clinics.

This paper describes the use of this modality on two chronic venous ulcers, using the single case experiment methodology. A treatment regime over a period of eight weeks was devised, whereby the patients received active therapy one week, followed by non-active the following week. This pattern was continued for the eight week period.

The results presented are encouraging, both in terms of ulcer size reduction and pain levels.
A survey of patients' perceptions of life with an ileo-anal pouch
Authors: Bond Carolyn F , Bailey Bob , Corry Dominic , Jones Di , Notter Joy
Published: August 2014

Since the advent of ileo-anal pouch surgery in the 1970s, there has been a gradual increase in the number of patients undergoing such surgery instead of the more traditional formation of an ileostomy. However, although the surgical procedures are clearly described and research is gradually accumulating regarding overall functioning and complications, little is known about the day to day practicalities of living with an ileo-anal pouch.

A survey of over 200 people with ileo-anal pouches was conducted to gather information about daily living from the patients perspective. This paper presents some of the findings from the survey, which provided a wealth of information that not only highlights physiological factors and how they impinge on life, but also gives an indication of how the respondents view their quality of life and what additional help they feel would enhance it.
Community health nursing: choice and opportunity
Authors: Moores Yvonne
Published: August 2014

In an exclusive interview for British Journal of Community Health Nursing, Yvonne Moores discusses her views on issues surrounding the choices and opportunities which are evolving for community nurses through the current series of Primary Care White Papers.
Eating disabilities following stroke
Authors: McLaren Susan
Published: August 2014

Recent evidence suggests that individuals who have suffered a stroke are at risk of developing protein-energy malnutrition. Deterioration in nutritional status, dehydration and an increased morbidity and mortality have been associated with the presence of dysphagia and other eating problems.

This paper reviews selected impairments in physical and cognitive functions which can impair food intakes and which may influence development of malnutrition in this vulnerable group, together with the interventions which may improve patient outcomes. Some of the vital aspects of successful management in the acute stage of illness are suggested here; including assessment of nutritional status, eating disability, prompt referral for expert advice on safe, adequate dietary provision, and radiological investigation of swallowing problems together with the use of appropriate aids to eating.
Use of community resources following inpatient and day case surgery for cataract
Authors: Buckingham Ken , Campbell Susan E , Olver Lynn R
Published: August 2014

The aim of this research was to discover whether day case surgery for cataract is associated with an increased use of community resources in comparison with inpatient surgery. Retrospective postal questionnaires were sent to determine the use of resources in the community. More detailed information was gathered by interviews with a sub-sample. The response rate was high (86 per cent). Generally, the reported use of community resources was low. The most important formal care services appeared to be those provided by nurses, general practitioners and home helps/domestic assistance. Inpatients rather than day case patients made greater use of these services. Day case patients made greater use of some forms of informal care. It appears that, day case cataract surgery does not result in high levels of community health care. This might in part be as a result of more rigorous discharge protocols for inpatients.
Analysis of district nurse workload in the community
Authors: Olver Lynn , Buckingham Ken
Published: August 2014

The aim of this paper is to demonstrate which diseases and conditions are most prevalent among the workload of district nurses. The findings reported here are the result of a large project, which considered ways of allocating resources to health authorities for expenditure on community health care. As part of the data set for this project, a number of NHS trusts provided diagnoses relating to contacts for each of the community services. The conditions which cause the largest proportion of district nurses' contacts are reported, along with the average duration of contact for each of these conditions. It is hoped this evidence will provide an insight into the workload of district nurses.
Health authority view of a primary care-led NHS
Authors: Lewis Richard
Published: August 2014

A primary care-led NHS is not simply a blueprint for a new delivery system, it is an elastic term applied to many different visions of future service delivery. Health authorities face a number of challenges – they must define their role and delegate their direct contracting role to others, while focusing on strategic commissioning/coherent strategic planning. The temptation to delegate wholly the task of clinical prioritisation to primary health care teams should be resisted, because health authorities must articulate public views and values as part of the clinical decision making process. With purchasing decisions increasingly made at primary care level, this will most likely result in an unintended/unrecognised impact on local health services development. However, the growth of locality commissioning groups of general practitioners (GPs) invites local planning and the development of quality assurance and improvement systems. With locality structures identifying the variability between primary health care teams, health authorities are well placed to facilitate a dialogue between primary care teams and between primary and seconday care clinicians.
Shifting the balance: nursing in primary health care
Authors: Mackenzie Ann , Ross Fiona
Published: August 2014

Fundamental changes over the last five years in the NHS, general practice and community care are influencing the shape of nursing in primary health care. This paper considers in particular the impact of general practitioner (GP) fundholding and discusses ways in which nursing in primary health care has responded in terms of changing skill mix in district nursing, health visiting and practice nursing and the growth of new nursing roles. The contribution of nursing to developing a needs-led and evidence-based service is discussed. This paper draws on exemplars from nursing practice in order to interpret policy and explain trends.
In search of excellence
Authors: Dilloway Mark
Published: August 2014

Atrilogy of ambitious White Papers, the implementation of the Culyer Report (Department of Health (DoH) 1994) and the 1996 Research Assessment Exercise (RAE96) are providing a complex environment for all those associated with primary and community care.

In response to the Culyer Report, both acute and community NHS trusts are forming research and development departments charged with maximising research income. Clinical and academic alliances are being forged throughout the country to take advantage of the funding opportunities, but the most successful will be those that received high ratings in RAE96.

Primary Care: The Future – Choice and Opportunity (DoH 1996a) has set the agenda for the foreseeable future with its central proposal to deregulate general practice, but the established organisations will be the ones most favoured to undertake the extensive research and development opportunities that will arise through these DoH initiatives. Innovations in patient care must be supported by published evidence that can contribute to RAE2000 if organisations are to prosper.
Romancing feminism: From women’s studies to women’s fiction
Authors: Reid Boyd Elizabeth
Published: August 2014

After more than a decade as a feminist researcher and teaching women’s studies at tertiary level, I decided to investigate a new direction. Driven in part by the demise of women’s studies in universities – an international phenomenon – and looking for something completely different, I attended my first Romance Writers of Australia conference. To my surprise, the scene was all too familiar: predominantly female participants and presenters, a collaborative leadership model, a supportive atmosphere and lots of purple. In this article I muse upon arguments that romance is a form of feminism. Going back to its history in the Middle Ages and its invention by noblewomen who created the notion of courtly love, examining its contemporary popular explosion and the concurrent rise of popular romance studies in the academy that has emerged in the wake of women’s studies, and positing an empowering female future for the genre, I propose that reading and writing romantic fiction is not only personal escapism, but also political activism. Now also a published romance novelist, I chart my own Harlequin Escape from the ivory tower to the boudoir.
‘That complete fusion of spirit as well as body’: Heroines, heroes, desire and compulsory demisexuality in the Harlequin Mills & Boon romance novel
Authors: McAlister Jodi
Published: August 2014

In the romance novels published by Harlequin Mills & Boon, sex and love are inextricably intertwined. The governing paradigm of the romance is a concept I have termed ‘compulsory demisexuality’. Someone who is demisexual only experiences sexual attraction to someone with whom they have an emotional bond. In the romance, this means that sex is only truly pleasurable when the partners are in love. The intersection of this paradigm with the notion of one true love means that the romance hero and heroine can only find real sexual pleasure with the other. This paradigm manifests differently between genders. Generally, heroines are demisexual, whereas heroes become demisexual. This change wrought in the hero is the key to understanding the romance text as a text of feminine victory: the ubiquitous happily-ever-after of the romance takes place in the heroine’s world. The way in which compulsory demisexuality has been realized within category romances has also changed over time. This article will discuss the historical evolution of the gendered relationship between sex and love in relation to two key texts, Denise Robins’s Shatter the Sky (1933) and Lynne Graham’s Desert Prince, Bride of Innocence (2009), focusing particularly on how the heroine’s sexual desire has complicated this relationship.
The warrior woman in Harlequin’s Bombshell Athena Force series
Authors: Chivers Marian , Speed Lesley , Tasker Meg
Published: August 2014

The theme of the warrior woman – the woman prepared to fight – appears in popular romance and in multiple time settings. This article will explore the way in which Silhouette Bombshell’s Athena Force series presents a series of romance heroines who are professional, trained warrior women. Rather than presenting these characters as a radical alternative to the more ‘traditional’ romance heroine, it will be shown that they attempt to accommodate a range of ideas about gender; they extend rather than reverse conventional ideas about femininity. There are, however, significant implications for the conventional romance plot as gender roles are unsettled and reconfigured. How are relationships between male and female warriors in the novels characterized, and how does this distinguish them from other contemporary romance fiction? Warrior women in fiction may be seen to subvert gender characteristics traditionally linked to biological traits and the conventional binary opposition between male and female gender roles. By stepping outside the accepted behaviour of females, the warrior woman makes us question those norms we may take for granted and provides another intriguing sub-genre for romance fiction.
Romance, romantic love and the ‘want of a fortune’
Authors: Fordham Helen , Milech Barbara
Published: August 2014

The English novel arose in the mid-eighteenth century as a cultural expression of a new middle class, a class that absorbed contemporary philosophies of individualism and democracy, and emerged within societies anchored in both representative government and capitalistic economies. Contemporary reality television gives us versions of the modern novel. Sometimes reality programmes, like the earliest novels, are episodic: each episode is linked by a single narrative voice or character and tells us about some issue. Sometimes these programmes present a season of episodes shaped by conventions of character, theme, conflict and resolution: together the episodes of each season form chapters in a story of ordinary lives so the audience can eavesdrop on others’ lives and draw life lessons. The Bachelor and The Bachelorette are typical of the latter kind of reality television. Generically, the programmes are related to the modern romance novel – they recount the story of finding ‘true love. Across nine months of staged presentation and accompanying interviews, they portray individuals looking for love, despite hostile adversaries, personal misunderstandings and disappointed expectations. This narrative arc leads to a climax where love is either found or missed, but either way it is represented as a complex synthesis of sexual frisson, friendship and respect. And all this occurs within the (occluded) context of someone winning $250,000. This article takes Jane Austen’s Pride and Prejudice ([1813] 1995) as a touchstone for understanding the appeal and meanings of The Bachelor and The Bachelorette as contemporary versions of the romance novel in order to explore how the idealization of love remains tied to not only notions of women’s individualism/liberation, but also to capitalism.
Polar bears and evil scientists: Romance, comedy and climate change
Authors: Walker Lisa
Published: August 2014

Climate change has been called the most boring subject the science world has ever had to present. Despite media stunts such as nude lie-ins to draw attention to the issue, recent polls show that the urgency of public opinion in relation to climate change has waned. This article argues that popular culture such as genre fiction can be an important communicative device in responding to climate change. It examines how a climate change theme can be developed in fiction and why romance and, in particular, romantic comedy, may be a suitable genre to make this issue relevant to the reader by connecting a global issue to its local effects. Climate change poses particular challenges to an author. My novel-in-progress, Melt (2013), is used as a case study of how these challenges may be met.
Architectural Review
Authors: Newman Emily L.
Published: August 2014

Building Upon History: An architectural review of the East Building at the St. Louis Art Museum and the Piano Pavilion at the Kimbell Art Museum
Exhibition Review
Authors: Batalion Judy
Published: August 2014

The Fashion World of Jean Paul Gaultier: From the Sidewalk to the Catwalk, Brooklyn Museum, 25 October–23 February 2014
‘Hey little rich boy, take a good look at me’: Punk, class and British Oi!
Authors: Worley Matthew
Published: August 2014

This article looks at the controversial music genre Oi! in relation to youth cultural identity in late 1970s and early 1980s Britain. By examining the six compilation albums released to promote Oi! as a distinct strand of punk, it seeks to challenge prevailing dismissals of the genre as inherently racist or bound to the politics of the far right. Rather, Oi! – like punk more generally – was a contested cultural form. It was, moreover, centred primarily on questions of class and locality. To this end, Oi! sought to realize the working-class rebellion of punk’s early aesthetic; to give substance to its street-level pretentions and offer a genuine ‘song from the streets’.
‘Prole Art Threat’: The Fall, the Blue Orchids and the politics of the post-punk working-class autodidact
Authors: Wilkinson David
Published: August 2014

In much of the writing that exists on The Fall, a persistent myth is perpetuated of the inscrutable character of Mark E. Smith. One of the contributing factors to this myth concerns Smith’s politics, commonly seen as ambiguous yet so far not analysed in detail. Here I shed some light on this issue. Furthermore, I wish to open up academic discussion on the work of The Blue Orchids, an outgrowth of The Fall, which developed an outlook inchoate in the original line-up, one which was lost when Smith became its driving force. There is a fascinating comparison to be made between the Fall and Blue Orchids on the basis of working-class negotiations of leftist post-punk at the dawn of Thatcherism. I examine how the two bands’ cultural production and political attitudes towards freedom and pleasure were shaped by residual countercultural and class-based influences. I then consider the divergent outcomes of Smith’s affinities with Thatcherism (which nevertheless retained oppositional elements) and The Blue Orchids’ mystical rejection of both the New Right and New Pop in favour of an oppositional ethos of fulfilment that was part G. I. Gurdjieff and part Worker’s Educational Association.
Book Review
Authors: Loydell Rupert
Published: August 2014

On the Periphery: David Sylvian – A Biography (The Solo Years), Christopher E. Young (2012) Heswall: Malin, 384 pp., ISBN: 9780992722807, h/bk, £24.99
Comparison of a direct enzymatic assay and polyacrylamide tube gel electrophoresis for measurement of small, dense low-density lipoprotein cholesterol
Authors: Vanavanan Somlak , Srisawasdi Pornpen , Rochanawutanon Mana , Kerdmongkol Jirapa , Kroll Martin H.
Published: August 2014

Small, dense low-density lipoprotein cholesterol (sdLDL-C) has been linked to the progression of cardiovascular disease. We compared two methods for determination of sdLDL-C, a direct enzymatic (ENZ) method and a polyacrylamide tube gel electrophoresis (PGE) assay, and investigated the associations of both sdLDL-C measurements with metabolic syndrome.

We analyzed 242 patient sera for sdLDL and atherosclerosis-related markers. The PGE method separates the intermediate-density lipoprotein particles into three midbands (MID-A to MID-C) and the LDL particles into seven subfractions (LDL1 to LDL7); the sdLDL-PGE result is calculated as the sum of cholesterol concentrations from LDL3 to LDL7.

The regression equation for sdLDL-C was [ENZ

The ENZ assay for sdLDL-C correlated well with the PGE method. The ENZ method measures a broader range of atherogenic lipoprotein particles than PGE and has the potential to identify subjects with vascular risk, thus contributing in directing specific interventions for cardiovascular prevention.
Circulating keratan sulfate as a marker of metabolic changes of cartilage proteoglycan in juvenile idiopathic arthritis; influence of growth factors as well as proteolytic and prooxidative agents on aggrecan alterations
Authors: Winsz-Szczotka Katarzyna , Komosińska-Vassev Katarzyna , Kuźnik-Trocha Kornelia , Siwiec Andrzej , Żegleń Bogusław , Olczyk Krystyna
Published: August 2014

The aim of this study was to evaluate the plasma keratan sulfate (KS) level as a potential marker of joint damage in children with juvenile idiopathic arthritis (JIA). The influence of growth factors as well as proteolytic and prooxidative agents on aggrecan alterations were evaluated in this study.

Plasma levels of KS, transforming growth factor β1 (TGF-β1), platelet-derived growth factor BB (PDGF-BB), a disintegrin and metalloproteinase with thrombospondin motifs 4 and 5 (ADAMTS-4 and ADAMTS-5), and thiol groups (TG) were quantified in samples obtained from 30 healthy subjects and 30 patients with JIA before and after treatment.

Increased (p<0.01) plasma KS was observed in JIA patients before treatment. Therapy resulted in a decrease in KS level. However, plasma KS level remained higher (p<0.05) than in controls. Increased levels of TGF-β1 (p<0.01) and PDGF-BB (p<0.05) in untreated JIA patients were recorded. Clinical improvement was accompanied by significant decrease in TGF-β1 and PDGF-BB, compared with a pretreatment condition and a control group. The concentrations of proteinases were characterized by different trends of alterations. When the ADAMTS-4 level increased (p<0.01) in the blood of untreated patients, the concentration of ADAMTS-5 was found to be reduced (p<0.0001), compared with controls. JIA treatment resulted in the normalization of ADAMTS-4 level. Plasma TG concentration was decreased only in untreated patients (p<0.05). We have revealed a significant correlation between plasma KS level and ADAMTS-4, TGF-β1, TG, C-reactive protein, and erythrocyte sedimentation rate levels.

Plasma KS level in JIA patients, reflecting the aggrecan structure, indicates that treatment that modifies inflammation simultaneously does not contribute to total regeneration of articular matrix components and signalizes the need for further treatment.
Auto-validation of complete blood counts in an outpatient’s regional laboratory
Authors: Froom Paul , Barak Mira
Published: August 2014

The rate of auto-validation is dependent on the ability of the laboratory information system (LIS) to integrate historical data, on the frequency and methods for identifying analyzer errors, and on the criteria for reflex testing, including the need for peripheral smear review. The rate of auto-validation in outpatient laboratories, however, is unclear.

We examined 45,925 consecutive complete blood count (CBC) test results (1 January, 2014–31 January, 2014) from patients aged 50±24 years. The LIS auto-validates all samples according to set criteria. Technicians validated test results when previous CBC test results were required to determine: 1) the need for peripheral slide review and/or sample rerun or 2) the need for reflex testing to detect autoimmune hemolytic anemia or β-thalassemia minor.

The auto-validation rates were 97.6% after rejecting results requiring validation to determine the need for a peripheral smear review and/or sample rerun. This decreased to 92.9% after including reflex testing to determine the reasons for normocytic and microcytic anemia. We estimated that auto-validation decreased the workload by 7.7–11.6 h per 3000 test results.

We conclude that very high auto-validation rates are possible in outpatient general laboratories, leading to conformity in the validation process and a considerable estimated savings in technician time. Further studies are needed in other settings.
Urinary neutrophil gelatinase-associated lipocalin and clinical outcomes in chronic kidney disease patients
Authors: Lin Hugo You-Hsien , Hwang Daw-Yang , Lee Su Chu , Kuo Hung-Tien , Kuo Mei-Chuan , Chang Jer-Ming , Tsai Jer-Chia , Hung Chi-Chih , Hwang Shang-Jyh , Chen Hung-Chen
Published: August 2014

Tubulointerstitial damage is a final common pathway of most renal diseases. Whether urinary neutrophil gelatinase-associated lipocalin (uNGAL), a biomarker for renal tubular damage, is of prognostic value for clinical outcomes in chronic kidney disease (CKD) patients has not been well investigated.

The uNGAL and proteinuria levels were measured among a cohort of 473 advanced CKD patients of various etiologies recruited during 2002–2009.

The estimated glomerular filtration rate (eGFR) was 32.3±22.0 mL/min/1.73 m

Elevated uNGAL in CKD patients is associated with risks for ESRD and probably CV events. UNPR could improve the prediction for ESRD.
Poly(η-caprolactone) layered silicate nanocomposites: effect of clay surface modifiers on the melt intercalation process
Authors: Pantoustier Nadège , Alexandre Michaël , Degée Philippe , Calberg Cédric , Jérôme Robert , Henrist Catherine , Cloots Rudi , Rulmont André , Dubois Philippe
Published: August 2014

Nanocomposites based on biodegradable poly(e-caprolactone) (PCL) and layered silicates (montmorillonite) modified by various alkylammonium cations were prepared by melt intercalation. Depending on whether the ammonium cations contain non-functional alkyl chains or chains terminated by carboxylic acid or hydroxyl functions, microcomposites or nanocomposites were recovered as shown by X-ray diffraction and transmission electron microscopy. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. The layered silicate PCL nanocomposites exhibited some improvement of the mechanical properties (higher Young’s modulus) and increased thermal stability as well as enhanced flame retardant characteristics as result of a charring effect. This communication aims at reporting that the formation of PCL-based nanocomposites strictly depends on the nature of the ammonium cation and its functionality, but also on the selected synthetic route, i.e. melt intercalation vs. in situ intercalative polymerization. Typically, protonated w-aminododecanoic acid exchanged montmorillonite allowed to intercalate ε -caprolactone monomer and yielded nanocomposites upon in situ polymerization, whereas they exclusively formed microcomposites when blended with preformed PCL chains. In other words, it is shown that the formation of polymer layered silicate nanocomposites is not straightforward and cannot be predicted since it strongly depends on parameters such as ammonium cation type and functionality together with the production procedure, i.e., melt intercalation, solvent evaporation or in situ polymerization.
(9,9-Dialkylfluorene-co-fluorenone) copolymers containing low fluorenone fractions as model systems for degradation-induced changes in polyfluorene-type semiconducting materials
Authors: Scandiucci de Freitas Patricia , Scherf Ullrich , Collon Maximilien , List Emil J. W.
Published: August 2014

This short communication describes synthesis, optical and electronic properties of novel 9,9-dialkylfluorene-co-fluorenone copolymers which function as model systems for degradation-induced changes in polyfluorene-type semiconducting materials. Only very small fractions of incorporated fluorenone building blocks lead to a dramatic change of the solid state properties (photo- and electroluminescence). The results are discussed in terms of intra- vs. intermolecular excitation energy transfer.
Simulation of bubble growth and collapse in linear and pom-pom polymers
Authors: Agarwal Uday S.
Published: August 2014

Existing approaches to simulate the bubble growth/collapse in viscoelastic liquids use the integral form of a constitutive equation, that can additionally be analytically integrated over the radial domain. Here we represent the process by a system of simultaneous partial differential equations, with fixed and finite boundaries. This enables a direct computer implementation with commercially available software, with little additional programming effort. The involved co-ordinate transformation preferably does not correspond to the material co-ordinates. The surrounding liquid can be simulated as being a finite film or of infinite extent, with simply a change in one computational parameter. We simulate hydrodynamically induced bubble dynamics in viscolelastic liquids, and estimate the flow strength (elongational strain rate) and its possible role in flow induced scission of polymer chains in liquids experiencing bubble collapse. Calculations are also performed to evaluate the influence of backbone and branch lengths when the surrounding fluid is a branched polymer melt, using the pom-pom model to describe the rheological behavior.
Formation and blood compatibility of thin layers of hyperbranched polymers on polyurethane films
Authors: Park Yong Soon , Kang Yong Soo , Chung Dong June
Published: August 2014

Two kinds of hyperbranched polymers, star-shaped poly(ethylene oxide) and poly(2-ethyl-2-oxazoline)-bound polyamidoamine dendrimer, were immobilized on polyurethane (PU) films using photoreactive azidophenyl groups. Immobilization of the hyperbranched polymers was verified by ATR FT-IR observations and contact angle measurements. Using photoreactive molecules, this study shows a unique method to modify polymer films without functional groups easily through immobilization of other polymers on the film surface. PU surfaces modified with immobilized hyperbranched polymer showed significantly reduced platelet adhesion, i.e. increased blood compatibility, as measured via UV spectrometry and scanning electron microscopy.
Copolymerization of styrene with methyl-substituted styrenes in the presence of titanium monometallocenes
Authors: Oliva Haydée , Leal Gracia , Ismayel Alida , Arribas Guillermo , Bronco Simona
Published: August 2014

This paper investigates the homo- and copolymerization of styrene with p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene and 2,4,6-trimethylstyrene using a Cp*TiCl3 (Cp: cyclopentadienyl) semimetallocene catalyst activated with methylaluminoxane. Syndiotactic homo- and copolymers were obtained only for the monosubstituted monomers. For the di- or trisubstituted monomers, reduced reactivities, stereoregularities, and degrees of polymerization were obtained with respect to the monosubstituted monomers. More specifically, the homopolymerization of 2,5-dimethylstyrene and 2,4,6-trimethylstyrene and their copolymerization with styrene was inhibited. The reason for this are combined steric and inductive effects. The presence of methyl groups in para position seems to inhibit crystallization of the syndiotactic polymers. In contrast, crystallinity was evidenced in the materials produced in the presence of m-methyl substituted monomers.
Flocculation characteristics of organo-modified clay particles in poly(L-lactide) / montmorillonite hybrid systems
Authors: Nam Pham Hoai , Fujimori Atsuhiro , Masuko Toru
Published: August 2014

The stacking characteristics of organo-modified montmorillonite particles in poly(L-lactide) / clay hybrids have been investigated through FT-IR measurements and transmission electron microscopy. The clay particles tend to flocculate with hydrogen bonding among the hydroxyl groups of the surfactant, those located at the edge of clay particles, and/or those existing at the ends of polylactide chains.
Optical methods to study the behaviour of supported metallocene catalysts during olefin polymerisation
Authors: Jang Yong-Jun , Bieber Kirsten , Naundorf Corinna , Nenov Nikolay , Klapper Markus , Müllen Klaus , Ferrari Daniela , Knoke Stefan , Fink Gerhard
Published: August 2014

It is demonstrated that modern optical methods allow for a very fast study of the behaviour of supported metallocene catalysts. By videomicroscopy several polymeric supports functionalised with cyclopentadiene units or poly(ethylene oxide) and poly(propylene oxide) chains and loaded with a metallocene were simultaneously studied. In this example it is shown that this method allows for a direct comparison of different catalysts under identical conditions in a single experiment. In addition by this experiment more detailed information on the behaviour of the supports can be obtained by studying the growth kinetics of single grains. As a second tool, laser scanning confocal fluorescence microscopy (LSCFM) was applied. Using dye-labelled supports LSCFM can be used as a very rapid tool to study the fragmentation of supports. This is demonstrated by 3D images showing the distribution of different support fragments in the polyethylene product particles.
Use of mesoporous silica as a reinforcing agent in rubber compounds
Authors: López Betty L. , Pérez León Dario , Mesa Mónica , Sierra Ligia , Devaux Eric , Camargo Mauricio , Campagne Christine , Giraud Stéphane
Published: August 2014

Mesoporous silica is used as filler for styrene-butadiene rubber (SBR); filler-polymer interactions are compared with those exhibited when Ultrasil silica (VN3) is used. A silane coupling agent is added to improve filler dispersion and its influence on the bound-rubber formation is also investigated. The bound-rubber content is higher for the mesoporous silica and increases further for the sample containing silane. The increase is explained by chemical interactions between filler and rubber and penetration of the rubber chains into the mesopores. This is confirmed by 13C solid-state NMR, IR spectroscopy and differential scanning calorimetry. Dynamic mechanical thermal analysis shows higher storage modulus for the rubber filled with mesoporous silica.
Thermo-responsive polymers and hydrogels in tissue engineering
Authors: Schmaljohann Dirk
Published: August 2014

Various aspects of synthetic polymers and hydrogels in tissue engineering are discussed. A series of graft copolymers based on either N-isopropylacrylamide or N,N-diethylacrylamide as polymer backbone, and on poly(ethylene glycol) as side chain were prepared and characterized. These polymers were then used for the preparation of surface-immobilized hydrogels. The thermo-responsive behaviour was studied on model substrates by ellipsometry. The use of thermoresponsive polymers for in vitro studies allows the control of surface properties and thus the stimulation of cell adhesion and detachment through temperature changes. The cellular response was investigated by cultivation of mouse fibroblasts on surface-immobilized, thermo-responsive hydrogels. It was demonstrated that mouse fibroblasts adhere and detach as a function of the temperature, which then could be related to the change in surface properties. The concept is finally extended to the preparation of patterned hydrogels, which were studied by imaging ellipsometry.
Poly(vinyl alcohol) nanofibres by electrospinning: influence of molecular weight on fibre shape
Authors: Jun Zeng , Hou Haoqing , Wendorff Joachim H. , Greiner Andreas
Published: August 2014

Poly(vinyl alcohol) (PVA) nanofibres were obtained by electrospinning of PVA/water solutions. Formation of beaded fibres combined with decreased fibre diameters was observed for low PVA concentrations. Electrospinning of blends of PVA of different molecular weight resulted in less bead formation and smaller fibre diameters as compared to corresponding homopolymers of similar viscosity.
Development of high-temperature separation techniques for the chemical composition analysis of ethylene - methyl methacrylate block copolymers
Authors: Heinz Lars-Christian , Graef Sven , Macko Tibor , Brüll Robert , Balk Sven , Keul Helmut , Pasch Harald
Published: August 2014

Ethylene - methyl methacrylate block copolymers are semicrystalline polymers that dissolve in organic solvents only at high temperatures. Accordingly, microstructure analysis by solution methods must be conducted at temperatures above 130°C. For the analysis of block copolymers of different compositions several analytical techniques were used, including high-temperature size-exclusion chromatography (SEC), hyphenated SEC-FTIR, and CRYSTAF (crystallisation analysis fractionation). While SEC with refractive index detection indicated a certain multimodality of the samples, SEC coupled with FTIR revealed that the samples were chemically inhomogeneous and may contain homo- and copolymer fractions. The presence of polyethylene and poly(methyl methacrylate) homopolymers in the copolymer samples was confirmed by CRYSTAF analysis, when the total concentration as well as the carbonyl group distribution were monitored separately. Chromatographic separation of the different sample components was achieved when liquid chromatography at critical conditions (LC-CC) was used. For the first time, true high-temperature LC-CC methods were developed operating at a column temperature of 140°C. As the stationary phase, silica gel was used. Suitable mobile phases were binary mixtures of 1,2,4-trichlorobenzene or 1,2- dichlorobenzene with cyclohexanone. Using LC-CC, the samples were separated into the copolymer and the homopolymer fractions.
Effect of organoclay impurities on mechanical properties of EVA-layered silicate nanocomposites
Authors: Bellucci F. , Camino G. , Frache A. , Ristori V. , Sorrentino L. , Iannace S. , Bian X. , Guardasole M. , Vaccaro S.
Published: August 2014

The purification process of commercial organoclays and the beneficial effect of the impurities removal on the mechanical properties of the EVA exfoliated and intercalated nanocomposites are described in this paper. Mechanical properties such as Young modulus are improved, without any change in morphology in the exfoliated nanocomposites and an improvement of intercalation degree in the intercalated nanocomposite as demonstrated by rheological test is observed.
Modification of NR/BR blend with unsaturated thermo plastic polyurethane; polyurethane synthesis, blend morphology, vulcanization, and vulcanizate properties
Authors: Šebenik Urška , Poljanšek Ida , Krajnc Matjaž
Published: August 2014

The unsaturated polyurethane (PU) was synthesized, characterized, and used in rubber compound. To study the effect of PU incorporation in the blend a systematic approach was used where PU was added to the natural rubber (NR), butadiene rubber (BR), and NR/BR blends. Different un-vulcanized and vulcanized compounds were characterized and the vulcanization process was investigated. It was observed that the synthesized PU was able to crosslink with the rubber compounds during the vulcanization process. The lowered temperature of melting indicated a better processability of the composites containing thermoplastic PU which melted at processing temperature, thereby allowing improvement in blend viscosity mold flow and to some extent in its homogeneity, although the mechanical properties such as hardness, tensile strength, modulus, and elongation at break did not differ significantly from the properties of elastomer blends without PU. The thermal stability of compounds with PU did not significantly worsen.
Hyperbranched Polymers from Maleic Anhydride and Diethanolamine: Synthesis, Characterization and Solution Rheology
Authors: Song Weiqiang , Song Qinghuan , Wu Chengxun
Published: August 2014

Novel hyperbranched polyesteramides have been synthesized from diethanolamine and maleic anhydride with ethylene glycol as a core monomer. No gelation occurred in the melt polymerization when diethanolamine and maleic anhydride were used in equimolar amount in the feed and when content of ethylene glycol was varied. Obtained products were soluble in water and in organic solvents such as NMF. The obtained polymers were characterized by using IR and NMR spectroscopies as well as GPC. It was suggested that the hyperbranched polyesteramides formed via a mechanism of a combination of esterification and addition reactions. The addition of a hydroxyl group to the - CH=CH- in maleic anhydride unit results in a formation of CH methine group. The ratio of -CH=CH- to CH in the polymers were estimated from 1H NMR spectrum as 0.140, 0.155, 0.175, 0.190 and 0.204 for polymers P1 to P5, respectively as the content of ethylene glycol charged decreased. The molecular weights and their polydispersities showed reverse dependences on the feed ratio of ethylene glycol to diethanolamine. The rheological properties of the polymers in aqueous solution were also examined. The polymers exhibit a steady increase of intrinsic viscosity with increasing molecular weight, and the Mark-Houwink exponent for these polymers is 0.26, which is much lower than 0.5 and suggested that these polymers possess a highly branched architecture. The polymer solutions showed a Newtonian behavior with steady shear viscosities independent of shear rate, which indicated the absence of a physical entanglement.
Variable morphologies of poly(vinyl acetate)–montmorillonite nanocomposites obtained by emulsion polymerization in the presence of poly(vinyl pyrrolidone)
Authors: Corobea Mihai-Cosmin , Uricanu Violeta , Donescu Dan , Deladi Szabolcs , Radovici Constantin , Serban Sever , Constantinescu Elena
Published: August 2014

Nanocomposites containing poly(vinyl acetate) and montmorillonite (MMT) were prepared using a one-batch emulsion polymerization recipe, assisted by poly (vinylpyrrolidone). The relative clay concentration with respect to the other reaction partners influences drastically the morphological units in the end-products. For low [MMT], well-defined, spherical PVAc particles are formed. At the other extreme, for high [MMT], production of polymeric, water-swollen aggregates is favored. Depending on the MMT/PVP ratio, the clay will be dispersed in the final polymer matrix in variable forms, from individual platelets to agglomerates of reformed tactoids.
Synthesis and characterization of new phenanthrolinetriether copolymers with rotaxane architecture
Authors: Farcas Aurica , Harabagiu Valeria
Published: August 2014

This paper is devoted to the preparation and characterization of new phenanthroline-triether copolymers with rotaxane architecture by reaction of complexes of α- or β- cyclodextrin and tri(ethylene glycol) ditosylate with 2,9-di(4-hydroxyphenyl)-1,10- phenanthroline, which is large enough to prevent dethreading of cyclodextrin molecules. Comparative 1H-NMR analysis of tri(ethylene glycol) ditosylate complexes and of rotaxane copolymers evidenced the lower cyclodextrin content in rotaxane copolymers as compared to the calculated values. The rotaxane copolymers present bimodal molecular weight distributions attributed to the separation of the fractions with different content of cyclodextrin threaded on the copolymer chain. As evidenced by thermogravimetric analysis, the rotaxane copolymers show higher thermal stability than its non-complexed homologue.
Synthesis and characterization of carboxyl endfunctionalized poly(methylidene malonate 2.1.2)
Authors: Studer Peggy , Riess Gérard
Published: August 2014

α-Carboxyl end-functionalized poly(methylidene malonates 2.1.2) were prepared by free-radical polymerization in the molecular weight range 5 000 - 10 000 by using 4,4'-azobis(4-cyanopentanoic acid) as a functional initiator. A functionality of one carboxyl group per chain could be obtained. On the contrary, it was demonstrated that chain transfer functionalization with mercaptans is not applicable in this case. A Michael addition reaction between the mercaptan and the monomer becomes the predominant side-reaction. The corresponding mercaptanmonomer adduct was characterized in detail by 1H and 13C NMR.