Publications by authors named "Katrin Winkel"

16 Publications

  • Page 1 of 1

Health-related quality of life in overweight German children and adolescents: do treatment-seeking youth have lower quality of life levels? Comparison of a clinical sample with the general population using a multilevel model approach.

BMC Public Health 2013 Jun 8;13:561. Epub 2013 Jun 8.

School of Public Health, Bielefeld University, Universitätsstraße 25, Bielefeld, D-33615, Germany.

Background: Health-related quality of life (HRQoL) is reduced in obese children and adolescents, especially in clinical samples. However, little is known regarding the HRQoL of moderately overweight youth. Moreover, several studies have indicated perceived overweight as a critical factor associated with lower HRQoL. Our main objective was to compare HRQoL between treatment-seeking overweight youth and the general adolescent population, whilst separating the effects of treatment-seeking status and perceived weight from those of objective weight status.

Methods: We compared the HRQoL of a clinical sample of overweight youth (N=137 patients, mean age±s.e.=11.24±0.15 years) with that of a representative population sample (N=6354, mean age=12.75±0.03 years). The population sample was subdivided into groups based on measured and perceived weight status. We used hierarchical linear models to compare HRQoL subscale scores (self- and parent-reported) between patients and population groups, adjusted for sociodemographic characteristics and taking into account clustering of the population sample.

Results: The parent-reported HRQoL of the treatment sample was significantly lower than that of other overweight youth perceived as 'too fat' on two subscales: 'self-esteem' and 'friends' (effect sizes: d=0.31 and 0.34, respectively). On other subscales, patients scored lower than adolescents perceived as having a 'proper weight' by their parents. The patterns for self-reported HRQoL in adolescents were different: patients reported higher self-esteem than other overweight youth feeling 'too fat' (d=-0.39). Female patients also reported higher physical well-being (d=-0.48), whereas males scored lowest among all compared groups (d=0.42-0.95). Patients did not differ from other overweight youth who felt 'too fat' with respect to other HRQoL dimensions. In general, lower HRQoL was primarily associated with a perceived, rather than actual, overweight status.

Conclusions: The treatment-seeking status of overweight youth was notably associated with low social well-being, which may therefore be the main motive for seeking treatment. Other HRQoL domains were not consistently reduced in treatment-seekers. Our results further indicate that perceived overweight rather than actual overweight impacts HRQoL in youth with a modest excess weight. These results have implications for interventions in overweight youth and in individuals who are dissatisfied with their weight.

Trial Registration: 'Obeldicks light' is registered at clinicaltrials.gov (NCT00422916).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1471-2458-13-561DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3683337PMC
June 2013

Changes in self-reported and parent-reported health-related quality of life in overweight children and adolescents participating in an outpatient training: findings from a 12-month follow-up study.

Health Qual Life Outcomes 2013 Jan 2;11. Epub 2013 Jan 2.

Bielefeld University, School of Public Health, Bielefeld, Germany.

Background: Health-related quality of life (HRQoL) was found to improve in participants of weight management interventions. However, information on moderately overweight youth as well as on maintaining HRQoL improvements following treatment is sparse. We studied the HRQoL of 74 overweight, but not obese participants (32.4% male, mean age = 11.61 ± 1.70 SD) of a comprehensive and effective six-month outpatient training at four time-points up to 12 months after end of treatment.

Methods: HRQoL was measured by self-report and proxy-report versions of the generic German KINDL-R, including six sub domains, and an obesity-specific additional module. Changes in original and z-standardized scores were analyzed by (2×4) doubly multivariate analysis of variance. This was done separately for self- and proxy-reported HRQoL, taking into account further socio-demographic background variables and social desirability. Additionally, correlations between changes in HRQoL scores and changes in zBMI were examined.

Results: There were significant multivariate time effects for self-reported and proxy-reported HRQoL and a significant time-gender interaction in self-reports revealed (p < .05). Improvements in weight-specific HRQoL were evident during treatment (partial η² = 0.14-0.19). Generic HRQoL further increased after end of treatment. The largest effects were found on the dimension self-esteem (partial η² = 0.08-0.09 for proxy- and self-reported z-scores, respectively). Correlations with changes in weight were gender-specific, and weight reduction was only associated with HRQoL improvements in girls.

Conclusions: Positive effects of outpatient training on generic and weight-specific HRQoL of moderately overweight (not obese) children and adolescents could be demonstrated. Improvements in HRQoL were not consistently bound to weight reduction. While changes in weight-specific HRQoL were more immediate, generic HRQoL further increased after treatment ended. An extended follow-up may therefore be needed to scrutinize HRQoL improvements due to weight management.

Trial Registration: clinicaltrials.gov NCT00422916.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1477-7525-11-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3547728PMC
January 2013

Effect of lifestyle intervention on features of polycystic ovarian syndrome, metabolic syndrome, and intima-media thickness in obese adolescent girls.

J Clin Endocrinol Metab 2011 Nov 31;96(11):3533-40. Epub 2011 Aug 31.

Department of Pediatric Endocrinology, Diabetes, and Nutrition Medicine, Vestische Hospital for Children and Adolescents, University of Witten/Herdecke, Dr. F. Steiner Strasse 5, D-45711 Datteln, Germany.

Context: Polycystic ovarian syndrome (PCOS) is associated with cardiovascular risk factors (CRF). Lifestyle intervention is regarded as therapy of choice even if studies in adolescent girls with PCOS are scarce.

Objective: Our objective was to analyze the impact of lifestyle intervention on menses irregularities, hyperandrogenemia, CRF, and intima-media thickness (IMT) in adolescent girls with PCOS.

Patients: Patients included 59 obese girls with PCOS aged 12-18 yr.

Intervention: Intervention was a 1-yr lifestyle intervention based on nutrition education, exercise training, and behavior therapy.

Main Outcome Measures: Menses cycles, IMT, waist circumference, blood pressure, fasting lipids, insulin, glucose, testosterone, dehydroepiandrosterone sulfate, androstenedione, and SHBG were evaluated.

Results: In contrast to the 33 girls without weight loss, the 26 girls reducing their body mass index during the lifestyle intervention (by a mean of -3.9 kg/m(2)) improved most CRF and decreased their IMT (by a mean of -0.01 cm). Testosterone concentrations decreased (by a mean of -0.3 nmol/liter) and SHBG concentrations increased (by a mean of +8 ng/ml) significantly in girls with weight loss in contrast to girls with increasing weight. The prevalence of amenorrhea (-42%) and oligoamenorrhea (-19%) decreased in the girls with weight loss. The changes in insulin in the 1-yr follow-up were significantly correlated to changes in testosterone (r = 0.38; P = 0.002) and SHBG (r = -0.35; P = 0.048). A linear regression model with changes in IMT as dependent variable demonstrated a significant association with changes in blood pressure and weight status but not with changes in testosterone.

Conclusions: Weight loss due to lifestyle intervention is effective to treat menses irregularities, normalize androgens, and improve CRF and IMT in obese adolescent girls with PCOS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1210/jc.2011-1609DOI Listing
November 2011

Cryoflotation: densities of amorphous and crystalline ices.

J Phys Chem B 2011 Dec 31;115(48):14167-75. Epub 2011 Aug 31.

Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

We present an experimental method aimed at measuring mass densities of solids at ambient pressure. The principle of the method is flotation in a mixture of liquid nitrogen and liquid argon, where the mixing ratio is varied until the solid hovers in the liquid mixture. The temperature of such mixtures is in the range of 77-87 K, and therefore, the main advantage of the method is the possibility of determining densities of solid samples, which are instable above 90 K. The accessible density range (~0.81-1.40 g cm(-3)) is perfectly suitable for the study of crystalline ice polymorphs and amorphous ices. As a benchmark, we here determine densities of crystalline polymorphs (ices I(h), I(c), II, IV, V, VI, IX, and XII) by flotation and compare them with crystallographic densities. The reproducibility of the method is about ±0.005 g cm(-3), and in general, the agreement with crystallographic densities is very good. Furthermore, we show measurements on a range of amorphous ice samples and correlate the density with the d spacing of the first broad halo peak in diffraction experiments. Finally, we discuss the influence of microstructure, in particular voids, on the density for the case of hyperquenched glassy water and cubic ice samples prepared by deposition of micrometer-sized liquid droplets.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jp204752wDOI Listing
December 2011

Equilibrated high-density amorphous ice and its first-order transition to the low-density form.

J Phys Chem B 2011 Dec 27;115(48):14141-8. Epub 2011 Jul 27.

Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

We investigate the downstroke transition from high- (HDA) to low-density amorphous ice (LDA) at 140 (H(2)O) and 143 K (D(2)O). The visual observation of sudden phase separation at 0.07 GPa is evidence of the first-order character of the transition. Powder X-ray diffractograms recorded on chips recovered from the propagating front show a double halo peak indicative of the simultaneous presence of LDA and HDA. By contrast, chips picked from different parts of the sample cylinder show either HDA or LDA. Growth of the low-density form takes place randomly somewhere inside of the high-density matrix. The thermal stability of HDA against transformation to LDA at ambient pressure significantly increases with decreasing recovery pressure and reaches its maximum at 0.07 GPa. A sample decompressed to 0.07 GPa is by ~17 K more stable than an unannealed HDA sample. An increasingly relaxed nature of the sample is also evident from the progressive disappearance of the broad calorimetric relaxation exotherm, preceding the sharp transition to LDA. Finally, we show that two independent thermodynamic paths lead to a very similar state of (relaxed) HDA at 140 K and 0.2 GPa. We argue that these observations imply an equilibrated nature of the amorphous sample in the pressure range of p ≲ 0.2 GPa and speculate that the observation of macroscopic phase separation involves two ultraviscous liquid phases at 140 K. This supports the scenario of a first-order liquid-liquid transition in bulk water.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jp203985wDOI Listing
December 2011

How many amorphous ices are there?

Phys Chem Chem Phys 2011 May 23;13(19):8783-94. Epub 2011 Mar 23.

Institute of Physical Chemistry University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

Many acronyms are used in the literature for describing different kinds of amorphous ice, mainly because many different preparation routes and many different sample histories need to be distinguished. We here introduce these amorphous ices and discuss the question of how many of these forms are of relevance in the context of polyamorphism. We employ the criterion of reversible transitions between amorphous "states" in finite intervals of pressure and temperature to discriminate between independent metastable amorphous "states" and between "substates" of the same amorphous "state". We argue that the experimental evidence suggests we should consider there to be three polyamorphic "states" of ice, namely low-(LDA), high-(HDA) and very high-density amorphous ice (VHDA). In addition to the realization of reversible transitions between them, they differ in terms of their properties, e.g., compressibility, or number of "interstitial" water molecules. Thus they cannot be regarded as structurally relaxed variants of each other and so we suggest considering them as three distinct megabasins in an energy landscape visualization.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c0cp02600jDOI Listing
May 2011

Obesity in disabled children and adolescents: an overlooked group of patients.

Dtsch Arztebl Int 2010 Apr 16;107(15):268-75. Epub 2010 Apr 16.

Institut für Pädiatrische Ernährungsmedizin, Vestische Kinder- und Jugendklinik Datteln, Universität Witten/Herdecke, 5711 Datteln, Germany.

Background: There is an ongoing debate concerning the relationship between disability and obesity in childhood and adolescence.

Methods: The literature available in Medline was selectively searched for the terms: "(children /OR/ adolescents) /AND/ disability /AND/ (overweight /OR/ obesity)". This search was complemented by inspection of journals in the fields of obesity, pediatrics, and neurology.

Results: A total of 38 relevant articles were identified. All studies agreed that the prevalence of overweight and obesity in children with disabilities was almost twice that in their non-disabled peers. No effective, long-lasting interventions for obesity in disabled children and adolescents have been published.

Conclusion: Since a high proportion of disabled children and adolescents are overweight or obese, effective strategies for preventing and managing excess weight need to be developed so as not to further endanger their social participation. Moreover, risk factors for overweight in disabled children and adolescents should be identified and their weight status carefully monitored.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3238/arztebl.2010.0268DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2864441PMC
April 2010

Reversibility and isotope effect of the calorimetric glass --> liquid transition of low-density amorphous ice.

Phys Chem Chem Phys 2010 Jan 20;12(3):708-12. Epub 2009 Nov 20.

Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

We here report differential scanning calorimetry (DSC) scans recorded by repeatedly heating the H(2)O (D(2)O) low density amorph (LDA) which was made by isothermal decompression of very high-density amorphous ice (VHDA) at 140 K from 1.1 to 0.006 GPa. These DSC scans show a glass --> liquid transition endotherm with an onset temperature (T(g)) of approximately 137 (140) K at a heating rate of 30 K min(-1) accompanied by an increase in heat capacity of approximately 1.7 (1.5) J K(-1) mol(-1). We establish the reversibility of this effect by thermally cycling between its glassy state below 137 K and its highly viscous liquid state at 149 K. All calorimetric signatures, including H/D isotope effect, are highly similar to the signatures in hyperquenched glassy water (HGW). We argue that the observation of almost identical calorimetric traces for HGW and LDA implies that there is no need to reassign HGWs T(g) to higher temperatures provided that the viscous liquid state connected to both LDA and HGW behaves as an ideally "strong" liquid in the Angell classification. We furthermore show that LDA prepared by isothermal decompression of VHDA is more crystallization-resistant than LDA made from high-density amorphous ice (HDA) by isobaric warming. We suggest that the former route via VHDA removes "nanocrystalline remnants" in LDA which are still present in the latter after pressure-amorphization of hexagonal ice to HDA at 77 K.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/b917662dDOI Listing
January 2010

Hexagonal ice transforms at high pressures and compression rates directly into "doubly metastable" ice phases.

J Chem Phys 2009 Dec;131(22):224514

Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

We report compression and decompression experiments of hexagonal ice in a piston cylinder setup in the temperature range of 170-220 K up to pressures of 1.6 GPa. The main focus is on establishing the effect that an increase in compression rate up to 4000 MPa/min has on the phase changes incurred at high pressures. While at low compression rates, a phase change to stable ice II takes place (in agreement with earlier comprehensive studies), we find that at higher compression rates, increasing fractions and even pure ice III forms from hexagonal ice. We show that the critical compression rate, above which mainly the metastable ice III polymorph is produced, decreases by a factor of 30 when decreasing the temperature from 220 to 170 K. At the highest rate capable with our equipment, we even find formation of an ice V fraction in the mixture, which is metastable with respect to ice II and also metastable with respect to ice III. This indicates that at increasing compression rates, progressively more metastable phases of ice grow from hexagonal ice. Since ices II, III, and V differ very much in, e.g., strength and rheological properties, we have prepared solids of very different mechanical properties just by variation in compression rate. In addition, these metastable phases have stability regions in the phase diagrams only at much higher pressures and temperatures. Therefore, we anticipate that the method of isothermal compression at low temperatures and high compression rates is a tool for the academic and industrial polymorph search with great potential.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.3271651DOI Listing
December 2009

Overweight children and adolescents--is there a subjective need for treatment?

Int J Public Health 2009 ;54(2):112-6

Institute of Public Health and Nursing Research (IPP), University of Bremen, P.O. Box 330 440, D-28334, Bremen, Germany.

Objectives: We report on the first months of recruitment for a study to evaluate outpatient training for moderately overweight youths.

Methods: Various recruitment strategies were employed, including media exposure, paediatricians, school events, and the distribution of flyers. Roughly 6 160 overweight and 4 720 obese children and adolescents of the target age range were estimated to live in the study area.

Results: Altogether, 172 families enrolled for participation. Only 38 enrolled children (22.1%), however, were overweight and thereby eligible for participation, 132 children (76.7%) were obese and two were normal weight. Most eligible participants were recruited via media or paediatricians.

Conclusions: Reaching overweight, but not obese, children and adolescents for intervention is difficult, where a low recognition of the condition in its less extreme form might be a particular problem.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00038-009-8004-xDOI Listing
July 2009

Raman spectroscopic study of the phase transition of amorphous to crystalline beta-carbonic acid.

Angew Chem Int Ed Engl 2009 ;48(15):2690-4

Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Austria.

What's the matter? The laboratory Raman spectra for carbonic acid (H(2)CO(3)), both for the beta-polymorph and its amorphous state, are required to detect carbonic acid on the surface of the pole caps of Mars in 2009, when the Mars Microbeam Raman Spectrometer lands on the planet. The picture shows a martian crater with ice of unknown composition, possibly containing carbonic acid (image adapted from DLR, with permission from ESA, DLR, and FU Berlin--G. Neukum).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.200805300DOI Listing
May 2009

Water polyamorphism: reversibility and (dis)continuity.

J Chem Phys 2008 Jan;128(4):044510

Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, AustriaInstitute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

An understanding of water's anomalies is closely linked to an understanding of the phase diagram of water's metastable noncrystalline states. Despite the considerable effort, such an understanding has remained elusive and many puzzles regarding phase transitions in supercooled liquid water and their possible amorphous proxies at low temperatures remain. Here, decompression of very high density amorphous ice (VHDA) from 1.1 to 0.02 GPa at 140 K is studied by means of dilatometry and powder x-ray diffraction of quench-recovered states. It is shown that the three amorphous states of ice are reversibly connected to each other, i.e., LDA<-->e-HDA<-->VHDA. However, while the downstroke VHDA-->e-HDA transition takes place in the pressure range of 0.06 GPaLDA transition takes place quasi-discontinuously at p approximately 0.06 GPa. That is, two amorphous-amorphous transitions of a distinct nature are observed for the first time in a one-component system-a first-order-like transition (e-HDA-->LDA) and a transition which is not first-order like but possibly of higher order (VHDA-->e-HDA). VHDA and e-HDA are established as the most stable and limiting states in the course of the transition. We interpret this as evidence disfavoring the hypothesis of multiple first-order liquid-liquid transitions (and the option of a third critical point), but favoring a single first-order liquid-liquid transition (and the option of a second critical point).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.2830029DOI Listing
January 2008

Carbonic acid: from polyamorphism to polymorphism.

J Am Chem Soc 2007 Nov 18;129(45):13863-71. Epub 2007 Oct 18.

Institute of General, Inorganic, and Theoretical Chemistry, University of Innsbruck, A-6020 Innsbruck, Austria.

Layers of glassy methanolic (aqueous) solutions of KHCO3 and HCl were deposited sequentially at 78 K on a CsI window, and their reaction on heating in vacuo in steps from 78 to 230 K was followed by Fourier transform infrared (FTIR) spectroscopy. After removal of solvent and excess HCl, IR spectra revealed formation of two distinct states of amorphous carbonic acid (H2CO3), depending on whether KHCO3 and HCl had been dissolved in methanol or in water, and of their phase transition to either crystalline alpha- or beta-H2CO3. The main spectral features in the IR spectra of alpha- and beta-H2CO3 are observable already in those of the two amorphous H2CO3 forms. This indicates that H-bond connectivity or conformational state in the two crystalline phases is on the whole already developed in the two amorphous forms. The amorphous nature of the precursors to the two crystalline polymorphs is confirmed using powder X-ray diffraction. These diffractograms also show that alpha- and beta-amorphous H2CO3 are two distinct structural states. The variety of structural motifs found within a few kJ/mol in a computational search for possible crystal structures provides a plausible rationalization for (a) the observation of more than one amorphous form and (b) the retention of the motif observed in the amorphous form in the corresponding crystalline form. The polyamorphism inferred for carbonic acid from our FTIR spectroscopic and powder X-ray diffraction studies is special since two different crystalline states are linked to two distinct amorphous states. We surmise that the two amorphous states of H2CO3 are connected by a first-order-like phase transition.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja073594fDOI Listing
November 2007

The relation between high-density and very-high-density amorphous ice.

Phys Chem Chem Phys 2006 Jun 18;8(24):2810-8. Epub 2006 May 18.

Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

The exact nature of the relationship between high-density (HDA) and very-high-density (VHDA) amorphous ice is unknown at present. Here we review the relation between HDA and VHDA, concentrating on experimental aspects and discuss these with respect to the relation between low-density amorphous ice (LDA) and HDA. On compressing LDA at 125 K up to 1.5 GPa, two distinct density steps are observable in the pressure-density curves which correspond to the LDA --> HDA and HDA --> VHDA conversion. This stepwise formation process LDA --> HDA --> VHDA at 125 K is the first unambiguous observation of a stepwise amorphous-amorphous-amorphous transformation sequence. Density values of amorphous ice obtained in situ between 0.3 and 1.9 GPa on isobaric heating up to the temperatures of crystallization show a pronounced change of slope at ca. 0.8 GPa which could indicate formation of a distinct phase. We infer that the relation between HDA and VHDA is very similar to that between LDA and HDA except for a higher activation barrier between the former. We further discuss the two options of thermodynamic phase transition versus kinetic densification for the HDA --> VHDA conversion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/b603159eDOI Listing
June 2006

High density amorphous ice from cubic ice.

Chemphyschem 2006 Jun;7(6):1203-6

Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Austria.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cphc.200600011DOI Listing
June 2006

Amorphous ice: stepwise formation of very-high-density amorphous ice from low-density amorphous ice at 125 K.

Phys Rev Lett 2006 Jan 18;96(2):025702. Epub 2006 Jan 18.

Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innsbruck, Austria.

On compressing low-density amorphous ice (LDA) at 125 K up to 1.6 GPa, two distinct density steps accompanied by heat evolution are observable in pressure-density curves. Samples recovered to 77 K and 1 bar after the first and second steps show the x-ray diffraction pattern of high-density amorphous ice (HDA) and very HDA (VHDA), respectively. The compression of the once formed HDA takes place linearly in density up to 0.95 GPa, where nonlinear densification and HDA --> VHDA conversion is initiated. This implies a stepwise formation process LDA--> HDA --> VHDA at 125 K, which is to the best of our knowledge the first observation of a stepwise amorphous-amorphous-amorphous transformation sequence. We infer that the relation of HDA and VHDA is very similar to the relation between LDA and HDA except for a higher activation barrier between the former. We discuss the two options of thermodynamic versus kinetic origin of the phenomenon.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevLett.96.025702DOI Listing
January 2006