bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and stability of B6, B, and B clusters
Authors: Li Qian Shu , Jin Qiao , Luo Qiong , Tang Au Chin , Yu Jian Kang , Zhang Hong Xing 
Published: July 2003

AbstractWe investigated various isomers of B6, B, and B clusters with ab initio [Hartree–Fock (HF), MP2)] and density functional theory (DFT) methods. Ten B6 isomers, 6 B isomers, and 6 B isomers are determined to be local minima on their potential energy hypersurfaces by the HF, B3LYP, B3PW91, and MP2 methods. Fourteen of these structures are first reported. The most stable neutral B6 cluster is the capped pentagonal pyramid (C5v), in agreement with the results reported previously. Hexagon B (C2h) isomer and fan‐shaped B (C2v) isomer are found to be the most stable on the cationic and anionic energy hypersurfaces, respectively. Natural bond orbital analysis suggests that there are three‐centered bonds in the most stable B6 neutral and ionic clusters. The multicentered bonds are responsible for the special stability of the lowest‐energy isomer. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 269–278, 2003
Direct solution of the Schrödinger equation by a parallel genetic algorithm: Cases of an exactly solvable 2‐D interacting oscillator and the hydrogen atom
Authors: Saha Rajendra , Bhattacharyya S. P. , Taylor Christopher D. , Zhao Yong , Cundari Thomas R. 
Published: July 2003

AbstractThe Schrödinger equation for an exactly solvable 2‐D interacting oscillator problem is solved numerically by application of a parallel genetic algorithm on a fixed coordinate grid (n × n). The critical energy evaluation step for the wave function strings is parallelized. A fast Fourier transform is used for computing the kinetic energy while the potential energy is obtained by quadrature. Comparison with the exact result indicates viability of the method. As a second case, the hydrogen atom problem is solved by the same method. Parallel performance of the code is also assessed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 243–250, 2003
Coupled‐perturbed Hartree–Fock theory for quasi–one‐dimensional periodic systems: Calculation of static and dynamic nonlinear optical properties of model systems
Authors: Martinez A. , Otto P. , Ladik J. 
Published: July 2003

AbstractAn alternative method to solve the coupled‐perturbed Hartree–Fock (CPHF) equations for infinite quasi–one‐dimensional systems is presented. The new procedure follows a proposal made by Langhoff, Epstein, and Karplus to obtain perturbed wavefunctions free from arbitrary phase factors in each order of perturbation. It is based on the intermediate orthonormalization of the perturbed wavefunctions (which is different from the usual one) and a corresponding selection of the Lagrangian multipliers. In this way it is possible to incorporate the orthonormalization conditions into the set of CPHF equations. Moreover, a new, advantageous procedure to determine the derivatives of the wavefunction with respect to the quasimomentum k is presented. We report calculations of the dipole moment, the polarizability α, and the first hyperpolarizability β for different polymers (poly‐HF, poly‐H2O, trans‐polyacetylene, polyyne, and polycarbonitrile) for different frequencies. These results are extensively compared with oligomer calculations. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 251–268, 2003
Effect of knowledge integration activities on students' perception of the earth's crust as a cyclic system
Authors: Kali Yael , Orion Nir , Eylon Bat‐Sheva 
Published: July 2003

AbstractSystems thinking is regarded as a high‐order thinking skill required in scientific, technological, and everyday domains. However, little is known about systems thinking in the context of science education. In the current research, students' understanding of the rock cycle system after a learning program was characterized, and the effect of a concluding knowledge integration activity on their systems thinking was studied. Answers to an open‐ended test were interpreted using a systems thinking continuum, ranging from a completely static view of the system to an understanding of the system's cyclic nature. A meaningful improvement in students' views of the rock cycle toward the higher side of the systems thinking continuum was found after the knowledge integration activity. Students became more aware of the dynamic and cyclic nature of the rock cycle, and their ability to construct sequences of processes representing material transformation in relatively large chunks significantly improved. Success of the knowledge integration activity stresses the importance of postknowledge acquisition activities, which engage students in a dual process of differentiation of their knowledge and reintegration in a systems context. We suggest including such activities in curricula involving systems‐based contents, particularly in earth science, in which systems thinking can bring about environmental literacy. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 545–565, 2003
Use of learner‐centered instruction in college science and mathematics classrooms
Authors: Walczyk, Jeffrey J. , Ramsey Linda L. 
Published: July 2003

AbstractLearner‐centered approaches to science and mathematics instruction assume that only when students are active participants will learning be deep, enduring, and enjoyable, and transfer to contexts beyond the classroom. Although their beneficial effects are well known, the extent to which learner‐centered practices are used in college classrooms may be low. Surveys of undergraduate science and math majors reveal general dissatisfaction with how courses in their majors are taught, and their number is half what it was 2 decades ago. In response, federally funded systemic reform initiatives have targeted increasing the use learner‐centered instruction in science and mathematics courses to improve undergraduate education generally and the training of preservice teachers specifically. Few data exist regarding how effective these initiatives have been or how frequently learned‐centered instruction occurs as assessed from faculty's perspective, which may not corroborate undergraduate perceptions. Accordingly, a survey was developed to assess the use of learner‐centered techniques and was administered to science and math professors of Louisiana over the Internet. The return rate was 28%. Analyses reveal that they are used infrequently, but when used, are applied to all aspects of teaching. Data also suggest that federal funding has been slightly effective in promoting its use. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 566–584, 2003
Development of an instrument for measuring cognitive conflict in secondary‐level science classes
Authors: Lee Gyoungho , Kwon Jaesool , Park Sang‐Suk , Kim Jung‐Whan , Kwon Hyeok‐Gu , Park Hac‐Kyoo 
Published: July 2003

AbstractBased on conceptual change theory, cognitive conflict is known as an important factor in conceptual change even though there are still questions about its positive and negative effects on science learning. However, there is no reliable method by which to assess the cognitive conflict students experience in their learning. The purpose of this research was to develop an instrument for measuring secondary students' cognitive conflict levels as they learned science. The results of this study indicate that our instrument is a valid and reliable tool for measuring cognitive conflict levels. Factor analysis supported the model that cognitive conflict consists of four constructs: recognition of an anomalous situation, interest, anxiety, and cognitive reappraisal of the conflict situation. Implications for instruction and possibilities for future research are discussed. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 585–603, 2003
A beneficial effect of a short‐term formal training course in epiluminescence microscopy on the diagnostic performance of dermatologists about cutaneous malignant melanoma
Authors: Troyanova Petranka 
Published: July 2003

Background: Epiluminescence microscopy (ELM) is a useful tool, which, in the hands of experienced dermatologists successfully helps in the diagnosis of early cutaneous malignant melanoma (CMM). As all imaging diagnostic methods, ELM also requires preliminary training of the physicians.Objective: The aim of the study was to evaluate a possible beneficial effect of a short‐term formal training course in ELM on the diagnostic performance of dermatologists about CMM.Methods: The test group consisted of 32 dermatologists. Tests were performed in the beginning and in the end of the teaching course. Every time a total 50 histologically proven pigmented skin lesions (PSLs) photographed without oil immersion—Surface microscopy (SM) and with oil immersion—ELM was presented by slide projection. To assess the effect on the diagnostic performance before and after short‐ term training the data concerning diagnoses were analysed for the following: sensitivity, specificity, positive predictive value, and negative predictive value, index of suspicion and diagnostic accuracy.Results: Before the training course the implementation of ELM leads to relative increasing of all studied indicators of ELM diagnosis towards SM diagnosis, but differences are not statistically significant (P > 0.05). After the course there is an improvement of diagnostic performance of dermatologists by ELM, manifested by enhancement of all indicators. The changes of the sensitivity, negative predictive value and diagnostic accuracy of ELM diagnosis was statistically significant (P < 0.05).Conclusion: The short‐term formal course in ELM has a beneficial effect on the diagnostic performance of dermatologists about CMM. The improvement of early detection of CMM requires dermatologists enhanced training and higher qualification in the field of dermoscopy.
Assessment of skin lesions and skin cancer using simple electrical impedance indices
Authors: Åberg Peter , Nicander Ingrid , Holmgren Ulf , Geladi Paul , Ollmar Stig 
Published: July 2003

Background/aims: Purpose of this investigation was to assess benign pigmented cellular nevus (BEN), basal cell carcinoma (BCC), dermatofibroma (DER), dysplastic nevus (DYS), and seborrheic keratoses (SEB) using in vivo non‐ invasive electrical impedance technique.Methods: Electrical impedance was measured at 258 BEN, 34 BCC, 17 DER, 35 DYS, and 26 SEB lesions. Controls were measured at healthy skin close to the lesions. The impedance was measured between 1 kHz and 1 MHz at five depth settings. After the impedance measurements the lesions were histopathologically diagnosed. The impedance spectra were parameterized to four indices prior to the statistical analysis of the data.Results: There were significant differences between the lesions and their controls for BEN (P < 0.001), BCC (P < 0.001), DYS (P < 0.01), and SEB (P < 0.01).Conclusions: There are clear statistical differences between impedance of common lesions and control skin. With some further developments, the impedance technique can be useful as a diagnostic decision support tool for skin cancer assessment.
Determination of antioxidant efficacy of cosmetic formulations by non‐invasive measurements
Authors: Vertuani S. , Ziosi P. , Solaroli N. , Buzzoni V. , Carli M. , Lucchi E. , Valgimigli L. , Baratto G. , Manfredini S. 
Published: July 2003

Background/aims: Antioxidants have been proposed, over the last decade, as functional ingredients for anti aging preparations and to prevent and modulate oxidative skin damages. Up to date, beside the photo‐induced oxidative skin damages model, none in vivo protocols have shown sufficient reproducibility for the validation of the antioxidant claim for a cosmetic finished product. To this aim, we have recently anticipated a new in vivo protocol based on a microinflammatory model, driven by reactive oxygen species. In the present study our model was validated by comparison with four different instrumental methods.Methods: The effects of a pre‐treatment of two different formulations based on antioxidant functional ingredients, were investigated on forearm skin of 15 healthy volunteers, and compared to a cosmetic base and control area. The instruments considered in the study were Chromameter (CR‐300 Minolta), Tewameter TM 210 (Courage‐khazaka, Cologne, Germany), Laser Doppler Perfusion Imager (PIM1.0 Lisca Development AB, Sweden), in comparison to DermAnalyzer®, an easy to use software program developed by us, using the CIE L*a*b* color space parameters.Results: The comparative measurements showed that the antioxidant formulations tested were all able to reduce, in different but statistically significant extent, the intensity of skin redness, and of cutaneous blood flow, when compared to control area (P < 0.0001).Conclusions: The methyl nicotinate (MN) based microinflammatory model, in conjunction with objective measure‐ ments, resulted an effective tool for in vivo assessment of oxidative skin injuries. In view of the high level of repeatability, short time of answer and simplicity, the procedure by us developed, is proposed as a possible protocol for the evaluation of in vivo efficacy of antioxidant functional ingredients in cosmetic formulations.
A numerical‐experimental method to characterize the non‐linear mechanical behaviour of human skin
Authors: Hendriks F. M. , Brokken D. , Van Eemeren J. T. W. M. , Oomens C. W. J. , Baaijens F. P. T. , Horsten J. B. A. M. 
Published: July 2003

Background/aims: Human skin is a complex tissue consisting of several distinct layers. Each layer consists of various components with a specific structure. To gain a better insight into the overall mechanical behaviour of the skin, we wish to study the mechanical properties of the different layers. A numerical‐experimental method was developed to characterize the non‐linear mechanical behaviour of human dermis.Methods: Suction measurements at varying pressures were performed on the volar forearm skin of 10 subjects aged 19–24 years old. Deformation of dermis and fat during suction was measured using ultrasound. The experiment was simulated by a finite element model exhibiting extended Mooney material behaviour to account for the non‐linear stress–strain relationship. An identification method is used to compare the experimental and numerical results to identify the parameters of the material model.Results: C
10, dermis was found to be 9.4 ± 3.6 kPa and C11, dermis to be 82 ± 60 kPa. A first rough estimate of C10, fat was 0.02 kPa.Conclusions: The resulting finite element model demonstrated its ability to describe the response of the skin to suction at various pressures. In the future, this method can be used to characterize the mechanical behaviour of different skin layers using various aperture sizes and to characterize the skin behaviour under various loading conditions.
Electrical impedance scanning: a new approach to skin cancer diagnosis
Authors: Glickman Yaël A. , Filo Orna , David Magda , Yayon Avner , Topaz Moris , Zamir Bosmat , Ginzburg Alexander , Rozenman Dganit , Kenan Gad 
Published: July 2003

Background/aims: Skin cancer diagnosis depends, to a great extent, on visual inspection and histopathological examination of excised tissues. The aim of this study is to evaluate the ability of electrical impedance scanning to differentiate between benign and malignant skin lesions.Methods: A preclinical study was conducted on 40 nude mice injected subcutaneously with a human melanoma strain. Impedance measurements were recorded every week to correlate electrical changes with tumor growth and histological findings. A clinical study was also performed on 178 human suspicious skin lesions before excision. The impedance measurements were correlated to the histopathological results.Results: Normalized conductivity and capacitance, recorded on growing skin tumors in nude mice, were shown to change relative to lesion size. Necrosis, present in most of the larger lesions, was associated with a decrease in the electrical conductivity. Similar electrical parameters were used to classify human melanoma lesions with 92% sensitivity and 67% specificity. In addition, four out of five BCC lesions were correctly diagnosed. Moreover, dysplastic lesions were diagnosed with 91% sensitivity and 59% specificity. For comparison, physicians diagnosed melanoma lesions with 75% sensitivity and 87% specificity and dysplastic lesions with 46% sensitivity and 80% specificity.Conclusions: The animal study showed that electrical impedance measurements reflect morphological changes related to the growth of a cancerous skin lesion. These findings are in agreement with a preliminary clinical study. Electrical Impedance Scanning can therefore be considered as an objective and non‐invasive tool for differentiation between benign and malignant skin lesions.
Collagen crosslinking and cell density have distinct effects on fibroblast‐mediated contraction of collagen gels
Authors: Redden Robert A. , Doolin Edward J. 
Published: July 2003

Background/purpose: Fibroblasts are actively and dynamically involved in wound healing (dermal regeneration, wound contraction, and scar contracture) and fibrosis. Fibroblast‐seeded collagen gels provide an in vitro model for these processes. Over time, fibroblasts will contract the gels, but the mechanisms are not completely understood. This research investigated the influence of cell density and collagen crosslinking on the contraction of fibroblast‐populated gels by varying seeding density and blocking the catalyzing enzyme lysyl oxidase, respectively.Methods: Collagen gels were seeded with fibroblasts at either 3 × 104 or 1 × 105 cells/mL and incubated with or without the lathyrogen β‐aminoproprionitrile (BAPN) for 8 days. In all, four experimental groups were analyzed: low cell density control, high cell density control, low density plus BAPN, and high density plus BAPN. Digital images were taken daily and gel area was calculated.Results: Contraction was dependent on cell concentration, with higher density gels being contracted to a greater extent. BAPN had no effect until after day 2 when it inhibited (high density) or almost completely blocked (low density) the gel contraction. BAPN also reduced total long‐term contraction.Conclusion: The results demonstrated a bimodal nature to fibroblast‐mediated gel contraction: a cell density‐dependent component, most likely mediated through cellular forces, and a delayed collagen crosslinking component that could be blocked by BAPN. In the long‐term, similar contraction rates among the four experimental groups, particularly between the two BAPN groups, implies that the collagen crosslinking effect is discrete and independent of cell density.
Effect of age, breast size, menopausal and hormonal status on mammographic skin thickness
Authors: Ulger Harun , Erdogan Nuri , Kumanlioglu Sadan , Unur Erdogan 
Published: July 2003

Background/purpose: The localized or generalized skin thickness detected on mammography may reflect an underlying pathology of breast or a systemic disease involving the skin. The aim of this report is to describe the range of normal breast skin thickness in women using a film‐screen mammographic technique.Methods: Measurement of the mammographic skin thickness over different parts of the breast was performed in 144 women who had normal findings in a combined mammographic and ultrasonographic examination. Patients were grouped as premenopause, postmenopause and surgical menopause who were under continuous oestrogen treatment. The skin thickness in four regions (superior, inferior, medial, lateral) of both breasts was compared, and their relations with age, breast size, menopausal and hormonal status were investigated. The interobserver reliability was tested in a small subgroup of patients.Results: Interobserver agreement was good for all measurements. The range of normal breast skin thickness was between 0.50 and 3.10 mm. There were no differences in skin thickness between the corresponding regions of the breasts, with significant differences between the regions in the same breast. While breast size increased with age, skin thickness decreased in all regions.Conclusion: The breast size, age, regional variations and hormonal status of the patients should be considered when defining the normal range of skin thickness in mammographic examinations. We assume that upper limit of mammographic skin thickness should be set as 3.0 mm, regardless of the focal spot size and film‐focus distance.
Dermatoglyphics in patients with eczema, psoriasis and alopecia areata
Authors: Pour‐Jafari H. , Farhud D. D. , Yazdani A. , Hashemzadeh Chaleshtori M. 
Published: July 2003

Background/aims: The study of patterns of fingerprints is important in anthropology and medical genetics, chiefly because of their diagnostic usefulness. In the present work, we studied the frequencies of various types of skin ridges of the first phalanx in patients with eczema, psoriasis and alopecia areata.Methods: In a double‐blind case‐control study, we determined the frequencies of fingerprints in 551 patients (240 cases with eczema, 164 cases with psoriasis and 147 cases with alopecia areata) as well as in general population of Hamadan City (control group: 188 males and 529 females). We compared the frequencies between various fingers, hands and sexes in all three case groups as well as between case groups and control group.Results: The frequencies of various types of fingerprints are presented in some tables. The results showed that frequencies are not statistically different according to types of fingers, hands (left or right) and sexes as well. But they are significantly different in various case groups and between case groups and control group.Conclusions: We can conclude that frequencies of various patterns of skin ridges differ in eczema, psoriasis and alopecia areata from normal population.
A rapid, accurate, and facile method to quantify the antioxidative capacity of topical formulations
Authors: Zhai Hongbo , Choi Myeong Jun , Arens‐Corell Michaela , Neudecker Birgit A. , Maibach Howard I. 
Published: July 2003

Background/aims: Various methodologies have been developed to quantify antioxidant activity. A simple, rapid and accurate method is demanded. This study examined the antioxidative status of a pH balanced vitamin E containing formulation versus its vehicle control utilizing a photochemiluminescence device.Methods/results: A pH balanced 5% Vitamin E containing formulation and its vehicle control were tested. The quantity of antioxidant capacity for the pH balanced vitamin E formulation and its vehicle control were 2.28 ± 0.05 and 0.16 ± 0.03, respectively. The pH balanced vitamin E formulation showed a significant (P < 0.001) higher antioxidant capacity compared to its vehicle control.Conclusions: This method not only provides quantitative data, but also is rapid, accurate, and facile in performance. The in vitro data obtained in this study require validation by in vivo studies to properly place them in context to alternate methods.