bluuebunny/crossref_metadata_2025 huggingface dataset:
Depressiveness and social relations of juvenile offenders deprived of their liberty
Authors: Hrncic Jasna
Published: September 2008

The article examines the interrelations between depressiveness and social relations of adolescents, deprived of their liberty due to their offences. The model of unipolar depression is proposed, that assumes that basic conditions for occurrence of depression are adversity and insufficiency of current and past, real or internalized affective relations with social environment, and inefficiency of adaptive mechanisms to overcome that state. 191 male juveniles 15 - 22 years of age, in residential and correctional institutions in Serbia, completed three self-rating scales of depression, and 18 self-rating scales of family and peer relations. The correlation between depression and social relations was 0.745 that explains even 55.50% of the variance. It was largely explained by negative and dismissive family and peer relations, and insufficient individuation in a family. Both family and peer variables gave significant mutually independent contribution to the explanation of depressiveness. Both current and past peer relations had significant mutually independent contribution to the explanation of depressiveness. Findings are in favor to proposed model of depression.
Characteristics of sensorineural hearing loss secondary to inner ear acoustic trauma
Authors: Spremo Slobodan , Stupar Zdenko
Published: September 2008

INTRODUCTION Cochlear damage secondary to exposure to acoustic trauma is the consequence of the acoustic energy effects on the hearing cells in Korti's organ. OBJECTIVE The objective was to assess the correlation between the degree of sensorineural hearing loss and the type of audiogram registered in acoustic trauma exposed patients. METHOD We analyzed 262 audiograms of patients exposed to acoustic trauma in correlation to 146 audiograms of patients with cochlear damage and hearing loss not related to acoustic trauma. "A" group consisted of acoustic trauma cases, while "B" group incorporated cases with hearing loss secondary to cochlear ischaemia or degeneration. All audiograms were subdivided with regard to the mean hearing loss into three groups: mild (21-40 dB HL), moderate (41-60 dB HL) and severe (over 60 dB HL) hearing loss. Based on audiogram configuration five types of audiogram were defined: type 1 flat; type 2 hearing threshold slope at 2 kHz, type 3 hearing threshold slope at 4 kHz; type 4 hearing threshold notch at 2 kHz; type 5 notch at 4 kHz. RESULTS Mild hearing loss was recorded in 163 (62.2%) ears in the acoustic trauma group, while in 78 (29.8%) ears we established moderate hearing loss with the maximum threshold shift at frequencies ranging from 4 kHz to 8 kHz. The least frequent was profound hearing loss, obtained in 21 (8%) audiograms in the acoustic trauma group. Characteristic audiogram configurations in the acoustic trauma patient group were: type 1 (N=66; 25.2%), type 2 (N=71; 27.1%), and type 3 (N=68; 25.9%). Audiogram configurations were significanly different in the acoustic trauma group in comparison to the cochlear ischaemia group of patients (p=0.0005). CONCLUSION Cochlear damage concomitant to acoustic trauma could be assessed by the audiogram configuration. Preserved hearing acuity at low and mild frequency range indicates the limited damage to the hearing cells in Korti's organ in the apical cochlear turn.
Ultrastructural investigation of root canal dentine surface after application of active ultrasonic method
Authors: Mitic Aleksandar , Mitic Nadica , Muratovska Ilijana , Stojanovska Vera , Popovska Lidija , Mitic Vladimir
Published: September 2008

INTRODUCTION The basic work principle of all ultrasonic techniques is the piezoelectric effect of producing high frequency ultrasounds of small length, which are transmitted over the endodontic extensions or canal instruments into the root canal. When in contact with the tissue, ultrasonic vibrations are converted into mechanical oscillations. Ultrasonic waves and the obtained oscillations along with the synergic effect of irrigation bring about the elimination of smear layer from the root canal walls. OBJECTIVE The aim of the study was to ultrastucturally examine the effect of smear layer removal from the walls of canals by the application of the active ultrasonic method without irrigation, that is by the application of ultrasound and irrigation using distilled water and 2.5% NaOCl. METHOD The investigation comprised 35 single-canal, extracted human teeth. After removal of the root canal content, experimental samples were divided into three groups. According to the procedure required, the first group was treated by ultrasound without irrigation; the second one by ultrasound with irrigation using distilled water; and the third group was treated by ultrasound and irrigation using 2.5% NaOCl solution. The control samples were treated by machine rotating instruments (Pro-File) and were rinsed by distilled water. RESULTS The obtained results showed that the ultrasonic treatment of the root canal without irrigation did not remove the smear layer. The dentine canals are masked, and big dentine particles are scattered on the intertubular dentine. The ultrasonic treatment by using irrigation with distilled water provides cleaner dentine walls and open dentine tubules but with smaller particles on the intertubular dentine. The ultrasound treatment by using irrigation with 2.5% NaOCl solution provides a clean intertubular dentine surface without a smear layer and clearly open dentine tubules. CONCLUSION Instrumentation of the root canal by application of ultrasound by using NaOCl as irrigation provides a clean dentine surface of the root canal without a smear layer.
Surgical treatment of abdominal tumors closely related to major blood vessels
Authors: Davidovic Lazar , Sindjelic Radomir , Savic Nebojsa , Kostic Dusan , Cvetkovic Slobodan , Kuzmanovic Ilija , Markovic Dragan , Markovic Miroslav , Cinara Ilijas , Maksimovic Zivan , Djoric Predrag , Jadranin Dragica
Published: September 2008

INTRODUCTION Radical operative treatment of abdominal tumors closely related to major blood vessels often demands complex vascular procedures. OBJECTIVE The aim of this paper was to present elementary principles and results of the complex procedures, based on 46 patients operated on at the Institute for Cardiovascular Diseases, Clinical Centre of Serbia, Belgrade, from January 1999 to July 2006. METHOD Primary localization of the tumor was the kidney in 14 patients, the suprarenal gland in 2, the retroperitoneum in 23 and the testis in 7 patients. Histologically, the most frequent were the following: renal carcinoma in 14 patients, teratoma in 7, liposarcoma in 5, fibrosarcoma and lymphoma in 3 patients. The tumor compressed abdominal aorta occurred in 3 cases, vena cava inferior in 5 and both the abdominal aorta and vena cava inferior in 11 cases. In 4 cases the tumor infiltrated the abdominal aorta, in 11 the vena cava inferior and in 8 both of them. In two patients, the tumor compressed the vena cava inferior and infiltrated the aorta; in two patients the aorta was compressed and the vena cava was infiltrated. In three cases only the exploration was performed due to multiple abdominal organ infiltration. The ex tempore biopsy showed the type of tumor in which the radical surgical treatment did not improve the prognosis. In 20 cases of tumor compression, subadventitional excision was performed. In 23 cases of infiltration, the tumor excision and vascular reconstruction had to be performed. Intraoperative blood cell saving and autotransfusion were applied in 27 patients. RESULTS The lethal outcome happened in 3 (6.5%) patients during hospitalization. In other patients all reconstructed blood vessels were patent during the postoperative hospitalization period. CONCLUSION Treatment of the abdominal tumors closely related to major blood vessels must be interdisciplinary, considering diagnostics, operability estimation and additional measures. Tumor reduction cannot improve long term prognosis, and has no major impact on life quality. There have been not many papers that analyze the long term results after such complex operations proving their appropriateness.
Early rehabilitation and cardiorespiratory response in children after correction of congenital heart defects
Authors: Petronic Ivana , Milincic Zeljka , Nikolic Dejan , Cirovic Dragana , Ilic Slobodan , Parezanovic Vojislav , Radlovic Vladimir , Knezevic Tatjana , Pavicevic Polina
Published: September 2008

INTRODUCTION Significant improvement in survival and quality of life in patients after the correction of congenital heart defects was enabled by the introduction of surgical procedures. Due to increased vulnerability in the period after defect correction, early rehabilitation have found its place in recovery. Various studies suggest good effects of a rehabilitation programme especially in the early rehabilitation period. OBJECTIVE In our study we wanted to stress the importance of early rehabilitation as well as its effects of implementation. METHOD We evaluated the children treated at the University Children's Hospital during a four-year period. All participants were divided into two groups according to age: the first group included children up to the age of one year, and the second group included those from the first till the third year of life. Patients were divided into two groups according to the presence of complications. We monitored children with 4 types of congenital heart defects: Tetralogy of Fallot, Transposition of the Great Arteries, Coarctation of the Aorta and Stenosis of the Aorta. All exercises were implemented twice daily. Out of the pulmonary system parameters we monitored saturation of oxygen during the entire programme. Other parameters that were evaluated were: heart rate, ECG and breathing frequency. RESULTS In the children with corrected defects, the most frequent complication was athelectasis especially in the group of patients till the first year of life. The patients with the onset of complications had a longer rehabilitation programme. Saturation of oxygen at the end of the programme was significantly elevated. CONCLUSION From the above-mentioned it can be concluded that individual rehabilitation assessment for every patient is needed. Early rehabilitation measures give sustained effects of well-being after completion of the programme.
Hashimoto's thyroiditis in children and adolescents
Authors: Markovic Slavica , Kostic Gordana , Igrutinovic Zoran , Vuletic Biljana
Published: September 2008

INTRODUCTION Hashimoto's thyroiditis (HT) is a common cause of goitre and hypothyroidism in children and adolescents. Spontaneous remission may occur in up to 50% patients, but the development of hypothyroidism is possible. OBJECTIVE We investigated the clinical manifestations, course and long-term outcome of HT. METHOD We reviewed charts of 43 children (36 females) with HT, mean age at presentation 12.3 years, and mean follow-up duration 4.6 years. RESULTS HT is five times more common in females. The common complaints leading to referral were goitre in 19 children (44.3%), diffuse in 17 children (89.5%). As to the prevalence of goitre, it accounted for significantly more referrals in females (14 girls, and 5 boys; 73.7% vs 26.3%, t-test; p<0.005). Goitre was either isolated in 15 (34.4%) or associated with other complaints in 4 children: anemia in 7 (16.2%), fatigue in 5 (11.8%), increased appetite in 4 (9.7%), weight gain in 3 (7.0%), growth retardation in 2 children (4.7%), at irregular menses in 3 pubertal girls. Hypothyroidism was present in 18 patients (41.1%), 7 (38.8%) on initial admission, and 11 (61.8%) had the mean follow-up duration of 4.6 years. There were 25 euthyroid HT patients (59.9%). The family history of the thyroid disease was positive in 16 children (37.1%) and 12 of them (71.4%) had hypothyroidism. There were 6 patients (13.9%) in whom the disease was associated with some other autoimmune disease. CONCLUSION HT is five times more common in females. The usual complaints leading to referral were diffuse goitre, which accounted for significantly more referrals in females. A positive family history of autoimmune thyroid disease is associated with a higher risk of hypothyroidism in children with HT. Hypothyroid patients may appear in higher percentage of children and adolescents than previously reported.
Impact of valproates on haemostasis and blood cell count in children
Authors: Igrutinovic Zoran , Obradovic Slobodan , Vuletic Biljana , Markovic Slavica
Published: September 2008

INTRODUCTION Epilepsy is a highly prevalent disease affecting 0.5-1.5% of the world's population. One of the most frequently used antiepileptics are valproates. These medicines show a negative impact on haemostasis and peripheral blood count. OBJECTIVE The objective of the study was to examine the negative impact of valproates on haemostasis and peripheral blood count in children and to analyse whether these disturbances were dependent on the dosage of valproates and drug level in blood. METHOD A two-year research was conducted. The research included: 35 children using valproates, 12 children using the therapy of both valproates and carbamazepine and 30 healthy children. Complete peripheral blood count, screening tests of haemostasis (bleeding time, prothrombin time, prothrombin ratio, activated partial thromboplastin time, fibrinogen) and capacity of thrombocyte aggregation research were done in all the children. RESULTS We found significantly more common frequency of leukopenia and neutropenia in children using valproates in comparison with the healthy children group. We also found the more common frequency of eosinophilia in comparison with healthy children. The children with the valproate therapy have lower approximate values of the number of platelets, fibrinogen and platelet aggregation in comparison with healthy children, but they have a higher approximate value of bleeding time and prothrombin time. These disturbances are in correlation with the dosage and the level of the medicine in blood. CONCLUSION Valproates have a negative effect on certain blood count parameters and haemostasis in children. Drug dosage and blood drug level are correlated with their negative impact on haemostasis parameters.
Long-term evaluation of undergraduate family medicine curriculum in Slovenia
Authors: Svab Igor , Petek-Ster Marija
Published: September 2008

Introduction In 1994, as a result of curriculum reform, the Ljubljana medical school established its first department of family medicine and introduced its first curriculum of family medicine. The new subject was well accepted by the students and the medical school. Nevertheless, there was no comprehensive analysis of the curriculum during this period. Objective Our aims were to assess the quality of teaching based on fulfilled expectations, pre-defined learning objectives and satisfaction in a 10-year period, and to measure changes in career preference towards family medicine. Method An analysis of two sets of questionnaires, routinely given to medical students in academic years 1997/1998 and 2006/2007, was made. Results Most of the students' expectations were met, and the level increased over ten years. The level of achievement of learning objectives has been high and increased over the ten-year period. Family medicine still receives high scores in students' satisfaction. Although there is evidence that the family medicine curriculum is well accepted and that it improves some of the attitudes towards family medicine, it does not influence the career choice of students. Conclusion The level of achievement of learning objectives increased with the experiences of the teachers. We improved the attitude of medical students toward general practice and general practitioners. We have not been successful in influencing career choice of students, which is an objective that is probably outside our reach.
Root canal treatment of mandibular second premolar tooth with taurodontism
Authors: Vujaskovic Mirjana , Karadzic Branislav , Miletic Vesna
Published: September 2008

INTRODUCTION Taurodontism is a morphoanatomical change in the shape of a tooth. An enlarged body of a tooth with smaller than usual roots is a characteristic feature. Internal tooth anatomy correlates with this appearance, which means that a taurodontal tooth has a large pulp chamber and apically positioned furcations. This dental anomaly may be associated with different syndromes and congenital discoders. CASE OUTLINE The case report presents the patient of a rare case of taurodontism in the mandibular second premolar with chronic periodontitis. Endodontic treatment was performed after dental history and clinical examination. Special care is required in all segments of endodontic treatment of a taurodontal tooth from the identification orifice, canal exploration, determining working length, cleaning and shaping and obturation of the root canal. Precurved K-file was used for canal exploration and location of the furcation. One mesial and one distal canal with the buccal position were identified in the apical third of the root canal. The working lengths of two canals were determined by radiographic interpretation with two K-files in each canal and verified with the apex locator. During canal instrumentation, the third canal was located in the disto-lingual position. The working length of the third canal was established using the apex locator. CONCLUSION Thorough knowledge of tooth anatomy and its variations can lead to lower percentage of endodontic failure. Each clinical case involving these teeth should be investigated carefully, clinically and radiographically to detect additional root canals. High quality radiographs from different angles and proper instrumentarium improve the quality of endodontic procedure.
Olanzapine-high potency antipsychotic drug inducing significant weight gain: A case report
Authors: Maric Nadja , Josifovic-Kostic Dragana , Vukovic Olivera , Britvic Dubravka , Jasovic-Gasic Miroslava
Published: September 2008

INTRODUCTION Olanzapine is a second generation antipsychotic (SGA) with a high level of therapeutic effectiveness in schizophrenia and other psychotic disorders. Along with the positive therapeutic effects, an increase of the body weight frequently occurs. According to the literature, the average weight gain is about 6-7 kg during several months of treatment. This could be valued as a moderate weight increase. CASE OUTLINE This article presents a case of a young female with schizophrenia, without clinical improvement with several antipsychotics (clozapine, risperidone, haloperidol) and with the occurrence of significant neurological side effects. The treatment started with olanzapine (baseline) was associated with good initial response (PANSS reduction 20% in the first two weeks) and the improvement was maintained further on (PANSS reduction 50% after 16 weeks). Significant increase (20 kg, 40%) in weight appeared during the following 16 weeks (BMI at baseline 17.9 kg/m2; BMI 16 weeks later 25.1 kg/m2). CONCLUSION High effectiveness of olanzapine in schizophrenia symptoms reduction was accompanied by a significant weight gain. However, this drug leads to impaired glucoregulation, dyslipidaemia etc. It also increases the risk of diabetes and cardio-vascular diseases, i.e. the main causes of mortality in schizophrenia after a suicide. Therefore, clinicians are suggested to focus on possible predictors of weight gain during olanzapine therapy, and act accordingly in order to prevent serious health consequences.
Cardiovascular morbidity and mortality risk factors in peritoneal dialysis patients
Authors: Jovanovic Dijana
Published: September 2008

Cardiovascular (CVS) morbidity and mortality in the endstage renal disease (ESRD) patients on peritoneal dialysis therapy is 10-30 folds higher than in general population. The prevalence of well known traditional risk factors such as age, sex, race, arterial hypertension, hyperlipidaemia, diabetes, smoking, physical inactivity is higher in the uraemic patients. Besides these, there are specific, nontraditional risk factors for dialysis patients. Mild inflammation present in peritoneal dialysis (PD) patients which can be confirmed by specific inflammatory markers is the cause of CVS morbidity and mortality in these patients. Hypoalbuminaemia, hyperhomocysteinaemia and a higher level of leptin are important predictors of vascular complications as well as CVS events in the PD patients. Plasma norepinephrine, an indicator of sympathetic activity, is high in the ESRD patients and higher in the PD patients than in the patients on haemodialysis (HD). Therefore, norepinephrine may be a stronger risk factor in the PD patients. The same applies to asymmetric dimethylargine (ADMA), an endogenous inhibitor of nitric oxide synthase, which is an important risk factor of CVS morbidity and mortality 15 % higher in the PD than the HD patients. Hyperphosphataemia, secondary hyperparathyroidism and high calcium x phosphate product have been associated with the progression of the coronary artery calcification and valvular calcifications and predict all-cause CVS mortality in the PD patients. Residual renal function (RRF) declines with time on dialysis but is slower in the PD than the HD patients. RRF decline is associated with the rise of proinflammatory cytokines and the onset of hypervolaemia and hypertension which increase the risk of CVS diseases, mortality in general and CVS mortality. In conclusion, it is very important to establish all CVS risk factors in the PD patients to prevent CVS diseases and CVS mortality in this population.
Chronic lymphocytic leukaemia: An immunobiology approach
Authors: Kostareli Efterpi , Smilevska Tatjana , Stamatopoulos Kostas , Kouvatsi Anastasia , Anagnostopoulos Achilles
Published: September 2008

B cell chronic lymphocytic leukaemia (CLL) is the most common adult leukaemia that follows an extremely variable clinical course. Several important prognostic parameters defining pathogenic and clinical subgroups of CLL have been identified and validated recently. The biological significance of immunoglobulin (Ig) heavy chain variable region gene (IgHV) mutational status and associated ZAP-70 over-expression, CD38 and chromosomal aberrations have enabled to identify patients at high risk for early disease progression and inferior survival. Moreover, studies of the B cell antigen receptor (BCR) structure and receptor signaling have been most helpful in revealing some new aspects of the biology of this disease. In particular, the analysis of IG genes has revealed that the expressed IgHV/IgKV/IgLV gene repertoires of CLL cells differ from those of normal B cells. A further unique feature of the CLL IG repertoire is the existence of subsets of cases with "stereotyped" BCRs. Accumulating molecular and phenotypic data support the notion that CLL development and evolution is not a simple scholastic event and strongly indicates a role for antigen in driving the cell of origin for at least some subsets of CLL cases.
Historical overview of carotid artery surgical treatment
Authors: Popov Petar , Jocic Dario , Babic Srdjan , Tanaskovic Slobodan , Jovanovic Predrag , Nenezic Dragoslav , Ilijevski Nenad , Radak Djordje
Published: September 2008

Since antiquity, there has been a mystery about the cerebral circulation function. Scientific methods were introduced in research at the end of the nineteenth century. During the first half of the last century, the problem of occlusive carotid disease was defined and the basis for the surgical treatment of carotid disease was established. The first contemporary reconstructive surgical procedures were performed in the middle of the last century, the time when successful surgical treatment of carotid disease began. Today, carotid endarterectomy is one the most frequently performed vascular surgical procedures of all, followed by very low morbidity and mortality rates.
Eutanazija i religija
Authors: Jerotic Vladeta
Published: September 2008

nema
Liquid phase sintering, II: Computer study of skeletal settling and solid phase extrication in a microgravity environment
Authors: Nikolic Z.S.
Published: September 2008

A two-dimensional numerical method based on the Brownian motion model and on the Densification model for simulation of liquid phase sintering in microgravity environment will be developed. Both models will be based on domain topology (two-dimensional particle representation) and control volume methodology and on three submodels for domain translation, solid skeleton formation and domain extrication. This method will be tested in order to conduct a study of diffusion phenomena and microgravitational effects on microstructural evolution influenced by skeletal settling combined with solid-phase extrication during liquid phase sintering of porous W-Ni system.
Some laws of a system with a constant amount of energy
Authors: Blagojevic D. , Popovic H. , Popovic Z. , Stefanovic D. , Stefanovic I.
Published: September 2008

In this paper, different relationships and functional dependences of a system with a constant energy U=const., have been analyzed. The combinatorial nature of this analysis enables the conclusion that a family of entropy curves i.e. ? (N, U), for U = const, have an envelope. The envelope theory is very important for consideration of long & short range order of statistic thermodynamic systems. Since, we analyzed a system for U=const, we could explain some non-continual properties of a material. Like an example of this statement, we observed the situation, which is caused by anomaly filling of electronic orbits during the transfer from d to f elements.
Optical glass compatibility for the design of apochromatic systems
Authors: Gruescu C. , Nicoara I. , Popov D. , Bodea R. , Hora H.
Published: September 2008

The design of apochromatic systems is difficult because of two problems: the glass sorts compatibility and the c1/ca arbitrary input ratio. The optical glass manufacturers offer a wide range of sorts, so that the choice of triplet compatible glasses becomes itself an important separate problem. The paper provides a solution of mathematical modeling for the glass compatibility and, practically, analyses the sorts presented by Schott GmbH. The original software provided 22 compatible glass triplets. The authors explored the possibilities of enlarging the c1/ca ratio from the value 0.6 indicated in the literature to a range of [0.5?0.8]. Therefore, they designed and analyzed a set of 88 triplets. A correct glass choice can insure twice-larger apertures than the traditional ones for best quality apochromats (diffraction-limited).
Preparation of biomorphic SiC ceramics
Authors: Egelja A. , Gulicovski J. , Devecerski A. , Ninic M. , Radosavljevic-Mihajlovic A. , Matovic B.
Published: September 2008

This paper deals with a new method for producing non-oxide ceramic using wood as a template. SiC with a woodlike microstructure has been prepared by carbothermal reduction reactions of Tilia wood/TEOS composite at 1873K. The porous carbon preform was infiltrated with TEOS (Si(OC2H5)4), as a source of silica, without pressure at 298K. The morphology of resulting porous SiC ceramics, as well as the conversion mechanism of wood to SiC ceramics, have been investigated by scanning electron microscopy (SEM/EDS) and X-ray diffraction analysis (XRD). Obtained SiC ceramics consists of ?-SiC with traces of ?-SiC.
Kinetics of CxNy formation on electrode surface using the electrochemical method
Authors: Chekhovskii A. , Tomila T. , Ragulya A. , Timofeeva I. , Ivanchuk A. , Bykov D. , Labunets T.
Published: September 2008

Powded CxNy coatings were deposited from acetonitrile on Ni, Si, and C surfaces at a voltage 500-2000 V by the electrochemical method. Electrolysis products were analyzed by IR spectroscopy, X-ray phase analysis and electron microscopy. According to FTIR data, at frequencies 1370 and 1530 cm-1, absorption bands characteristic for stretching C-N and C=N oscillations are observed. The obtained results indicate that the deposition process occurs in a different manner in each specific case, i.e., the kinetics of the electrode depends on the electrode material (Ni, Si, and C).
History and challenges of barium titanate: Part I
Authors: Vijatovic M.M. , Bobic J.D. , Stojanovic B.D.
Published: September 2008

Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric, ferroelectric and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 called perovskites. Barium titanate can be prepared using different methods. The synthesis method depends on the desired characteristics for the end application. The used method has a significant influence on the structure and properties of barium titanate materials. In this review paper, Part I contains a study of the BaTiO3 structure and frequently used synthesis methods.
Optical properties of GaAs 2D Archimedean photonic lattice tiling with the p4g symmetry
Authors: Jovanovic Dj. , Gajic R. , Hingerl K.
Published: September 2008

In this paper we present our investigation of 2D Archimedean lattice photonic crystals with p4g space group symmetry. The structures are made of GaAs both as air holes and dielectric rods in air. In order to analyze the photonic crystal optical properties we performed calculations of the band structures, equi-frequency contours and electromagnetic propagation through the basic structures and waveguides. In addition, we investigated negative refraction and left-handedness in the p4g photonic crystal.
Influence of excess sodium ions on the specific surface area formation in a NiO-Al2O3 catalyst prepared by different methods
Authors: Lazic M.M. , Hadnadjev M.S. , Boskovic G.C. , Obadovic D.Z. , Kiss E.E.
Published: September 2008

The influence of sodium ions on the specific surface area of a NiO-Al2O3 catalyst in dependence of nickel loading (5, 10, and 20 wt% Ni), temperature of heat treatment (400, 700 and 1100oC) and the method of sample preparation was investigated. Low temperature nitrogen adsorption (LTNA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied for sample characterization. Dramatic differences in the specific surface area were registered between non-rinsed and rinsed Al2O3 and NiO-Al2O3 samples. The lagged sodium ions promote sintering of non-rinsed catalyst samples.
Recent advances in CIM technology
Authors: Zlatkov B.S. , Griesmayer E. , Loibl H. , Aleksic O.S. , Danninger H. , Gierl C. , Lukic L.S.
Published: September 2008

In this article the PIM (Powder Injection Moulding) technology is described in brief. After that the benefits and advantages were analyzed and summarized. Ceramic injection moulding (CIM) process was analyzed in more detail: CIM- alumina, CIM-zirconia and CIM ferrites as the most common technical ceramics in CIM ceramic parts production, medical applications and accessories in chemical laboratories, and cores in electronic inductive components. After that our results for CIM barium hexaferrite and piezo ceramics (barium titanate) are given. The main powder characteristics, the shrinkage and density and the main electrical characteristics of the sintered samples were compared for the isostatically pressed PM (powder metallurgy) and CIM formed samples. SEM fractographs of CIM and PM samples are given for CIM green parts, debinded (white) parts and sintered parts, and PM green parts and sintered parts. The results obtained were compared to literature data before they were applied in ceramic components production.
Effect of Cu addition and heat treatment self-propagating high temperature synthesis reaction in Al-Ti-C system
Authors: Li Y.X. , Hu J. , Liu Y.H. , Guo Z.X.
Published: September 2008

Effect of Cu addition and heat treatment on the self-propagating high temperature synthesis reaction have been investigated. The results show that Cu reacts with Al to form Al2Cu phase. With the addition of Cu, the combustion temperature of the system decreases and the porosity of the products is reduced, the size of TiC particulate decreases in the SHS reaction products. Specially, when heat treatment is carried out for the sintering products at 800 ?C, the rigid framework (sintering neck) between TiC particles was formed.
On the probability of an undetected surface-breaking crack
Authors: Achenbach J.D. , Kulkarni S.S.
Published: September 2008

Surface-breaking fatigue cracks are common defects in metal components subjected to cyclic loads. Such cracks tend to propagate in stress fields that are below the critical stress level for static loading. An important part of a damage tolerant design philosophy is the requirement that surface-breaking cracks should be detectable before they reach a critical depth. In this paper, we consider a surface-breaking crack in a two-dimensional geometry, whose original depth is defined by a probability density function. The increase of the crack depth with number of cycles is governed by Paris law, and the detectability depends on a probability of crack detection (POD). Based on this information we determine the probability that the crack depth will have exceeded a prescribed critical value at a specified number of cycles.
Micromechanical investigation of soil plasticity using a discrete model of polygonal particles
Authors: Alonso-Marroquin Fernando , Muhlhaus Hans , Herrmann Hans
Published: September 2008

The mechanical behavior of soils has been traditionally described using continuum-mechanics-based models. These are empirical relations based on laboratory tests of soil specimens. The investigation of the soils at the grain scale using discrete element models has become possible in recent years. These models have provided valuable understanding of many micromechanical aspects of soil deformation. The aim of this work is to draw together these two approaches in the investigation of the plastic deformation of non-cohesive soils. A simple discrete element model has been used to evaluate the effect of anisotropy, force chains, and sliding contacts on different aspects of soil plasticity: dilatancy, shear bands, ratcheting etc. The discussion of these aspects raises important questions such as the width of shear bands, the origin of the stress-dilatancy relation, and the existence of a purely elastic regime in the deformation of granular materials.
Micromechanical modeling of sulphate corrosion in concrete: Influence of ettringite forming reaction
Authors: Basista M. , Weglewski W.
Published: September 2008

Two micromechanical models are developed to simulate the expansion of cementitious composites exposed to external sulphate attack. The difference between the two models lies in the form of chemical reaction of the ettringite formation (through-solution vs. topochemical). In both models the Fick's second law with reaction term is assumed to govern the transport of the sulphate ions. The Eshelby solution and the equivalent inclusion method are used to determine the eigenstrain of the expanding ettringite crystals in microcracked hardened cement paste. The degradation of transport properties is studied in the effective medium and the percolation regime. An initial-boundary value problem (2D) of expansion of a mortar specimen immersed in a sodium sulphate solution is solved and compared with available test data. The obtained results indicate that the topochemical mechanism is the one capable of producing the experimentally observed amount of expansion.
Mechanics based statistical prediction of structure size and geometry effects on safety factors for composites and other quasibrittle materials
Authors: Bazant Zdeněk
Published: September 2008

The objective of this paper1 is a rational determination of safety factors of quasibrittle structures, taking into account their size and shape. To this end, it is necessary to establish the probability density distribution function (pdf) of the structural strength. For perfectly ductile and perfectly brittle materials, the proper pdf's of the nominal strength of structure are known to be Gaussian and Weibullian, respectively, and are invariable with structure size and geometry. However, for quasibrittle materials, many of which came recently to the forefront of attention, the pdf has recently been shown to depend on structure size and geometry, varying gradually from Gaussian pdf with a remote Weibull tail at small sizes to a fully Weibull pdf at large sizes. This recent result is reviewed, and then mathematically extended in two ways: 1) to a mathematical description of structural lifetime as a function of applied (time-invariable) nominal stress, and 2) to a mathematical description of the statistical parameters of the pdf of structural strength as a function of structure size and shape. Experimental verification and calibration is relegated to a subsequent journal article.
Failure modes of composite sandwich beams
Authors: Gdoutos E. , Daniel I.M.
Published: September 2008

A thorough investigation of failure behavior of composite sandwich beams under three-and four-point bending was undertaken. The beams were made of unidirectional carbon/epoxy facings and a PVC closed-cell foam core. The constituent materials were fully characterized and in the case of the foam core, failure envelopes were developed for general two-dimensional states of stress. Various failure modes including facing wrinkling, indentation failure and core failure were observed and compared with analytical predictions. The initiation, propagation and interaction of failure modes depend on the type of loading, constituent material properties and geometrical dimensions.
Elastoplastic damage micromechanics for elliptical fiber composites with progressive partial fiber debonding and thermal residual stresses
Authors: Ju J.W. , Yanase K.
Published: September 2008

Incorporating the interfacial damage and thermal residual stresses, an elasto-plastic damage formulation is proposed to predict the overall transverse mechanical behavior of continuous elliptical-fiber reinforced ductile matrix composites within the framework of micromechanics and homogenization. Based on the concept of equivalent inclusion and taking the progressive interfacial debonding angle into consideration, partially debonded fibers are replaced by equivalent orthotropic, perfectly bonded fibers. Three interfacial damage modes are considered. The Weibull's probabilistic function is adopted to describe the varying probability of progressive partial fiber debonding. The effective elastic moduli of four-phase composites, composed of a ductile matrix and randomly located yet unidirectionally aligned fibers are derived by a micromechanical formulation. Thermal residual stresses are taken into account through the concept of thermal eigenstrain to investigate the effects of the manufacturing processinduced residual stresses. Employing the micromechanical approximation, the overall stress-strain responses and the effective yield function are formulated with the thermal eigenstrain. When comparing with the available experimental data, significant effects of thermal residual stresses are discussed. Moreover, the effects of the interfacial strengths and the cross- sectional shapes of fibers on the mechanical behaviors of composites are systematically investigated.
Thermodynamic analysis based on the second-order variations of thermodynamic potentials
Authors: Lubarda Vlado
Published: September 2008

An analysis of the Gibbs conditions of stable thermodynamic equilibrium based on the constrained minimization of the four fundamental thermodynamic potentials, is presented with a particular attention given to the previously unexplored connections between the second-order variations of thermodynamic potentials. These connections are used to establish the convexity properties of all potentials in relation to each other, which systematically deliver thermodynamic relationships between the specific heats, and the isentropic and isothermal bulk moduli and compressibilities. The comparison with the classical derivation is then given.
Mechanics of complex bodies: Commentary on the unified modeling of material substructures
Authors: Mariano Paolo
Published: September 2008

Basic issues of the general model-building framework of the mechanics of complex bodies are discussed. Attention is focused on the representation of the material elements, the conditions for the existence of ground states in conservative setting and the interpretation of the nature of the various balance laws occurring.
On elastic response of disordered triangular lattice during dynamic loading
Authors: Mastilovic Sreten
Published: September 2008

The present investigation focuses on an observation regarding the initial elastic response of a triangular geometrically and structurally disordered lattice during medium-to-high strain rate loading. Namely: a transition from the short-time modulus of elasticity to the long-time one, which is not accompanied by the corresponding change of the stiffness tensor. It is demonstrated that the difference between the two moduli is, in the case of the homogeneous biaxial test simulations performed herein, a consequence of the geometrical and structural disorder "quenched" within the lattice. The investigation is performed on the triangular lattice with the first-neighbor central interactions under practically identical in-plane conditions over eight decades of strain rate.
Nanoparticles and the influence of interface elasticity
Authors: Changwen Mi , Kouris Demitris
Published: September 2008

In this manuscript, we discuss the influence of surface and interface stress on the elastic field of a nanoparticle, embedded in a finite spherical substrate. We consider an axially symmetric traction field acting along the outer boundary of the substrate and a non-shear uniform eigenstrain field inside the particle. As a result of axial symmetry, two Papkovitch-Neuber displacement potential functions are sufficient to represent the elastic solution. The surface and interface stress effects are fully represented utilizing Gurtin and Murdoch's theory of surface and interface elasticity. These effects modify the traction-continuity boundary conditions associated with the classical continuum elasticity theory. A complete methodology is presented resulting in the solution of the elastostatic Navier's equations. In contrast to the classical solution, the modified version introduces additional dependencies on the size of the nanoparticles as well as the surface and interface material properties.
Hysteretic behavior modeling of elastoplastic materials
Authors: Sumarac Dragoslav , Medjo Bojan , Trisovic Natasa
Published: September 2008

In the present paper the Preisach model of hysteresis is applied to model cyclic behavior of elasto-plastic material. Rate of loading and viscous effects will not be considered. The problem of axial loading of rectangular cross section and cyclic bending of rectangular tube (box) will be studied in details. Hysteretic stress-strain loop for prescribed history of stress change is plotted for material modeled by series connection of three unite element. Also moment-curvature hysteretic loop is obtained for a prescribed curvature change of rectangular tube (box). One chapter of the paper is devoted to results obtained by FEM using Finite Element Code ABAQUS. All obtained results clearly show advantages of the Preisach model for describing cyclic behavior of elasto-plastic material.
Adoption of Sarbanes-Oxley Measures by Nonprofit Organizations: An Empirical Study
Authors: Iyer Venkataraman M. , Watkins Ann L.
Published: September 2008

SYNOPSIS: This paper reports the results of a survey of 215 nonprofit organizations to determine the degree to which these organizations have voluntarily adopted provisions of the Sarbanes-Oxley Act of 2002 (SOX). The authors believe that this research is timely and important as several states are considering implementing regulation that would have implications for stricter accountability measures for nonprofit organizations. Results indicate that many of the nonprofits in this survey have either already adopted governance measures similar to those prescribed by SOX or are in the process of doing so. The regression results indicate that size of budget, size of the board of directors, and proportion of independent members on the board are significantly related to the presence of an audit committee. Organizations engaging external or internal auditors are more likely to have a code of conduct and have periodic assessments of internal controls. The presence of an internal audit function is also significantly related to management certification of financial reports. The regression analysis on a composite SOX measure (which was calculated by summing the responses to questions on adoption of an audit committee, code of conduct, whistleblower protection, management certification of financial reports, and periodic assessments of internal controls) indicates that the presence of an external and/or an internal audit is significantly related to the adoption of such SOX measures.
Effectiveness of Pit and Fissure Sealants in Reducing White Spot Lesions during Orthodontic Treatment
Authors: Benham Adam W. , Campbell Phillip M. , Buschang Peter H.
Published: September 2008

Objective: A pilot investigation was performed to test the null hypothesis that highly filled (58%) resin sealants do not prevent white spot lesions in patients undergoing active orthodontic treatment.

Materials and Methods: A split-mouth design was applied to 60 healthy patients, with the sealant randomly allocated to either the right or the left side of each jaw. The sealant was applied to the incisors and canines from the gingival surface of the bracket to the free gingival margin. The contralateral teeth had the same type of bracket with no sealant. Sealants were placed on the experimental teeth 2 weeks to 3 months after initial bonding and were removed after 15 to 18 months. Intraoral photographs, visual assessments, and DIAGNOdent (KaVo Dental Corporation, Lake Zurich, Ill) measurements were used to assess white spot lesions after sealant removal.

Results: Six lesions on the teeth with sealants were identified visually, compared with 22 lesions on the teeth without sealants. The teeth without sealants had 3.8 times the number of white spot lesions than were noted on the sealed teeth. These sealants showed no visible signs of discoloration. The DIAGNOdent measured statistically significant differences between sealed and unsealed teeth in the maxilla (P < .001) and in the mandible (P = .010). DIAGNOdent measurements also showed a difference between sealed and unsealed teeth after the 28 teeth with visible lesions were excluded.

Conclusion: The hypothesis was rejected. Ultraseal XT Plus clear sealant (Ultradent Products, South Jordon, Utah) produced a significant reduction in enamel demineralization during fixed orthodontic treatment and should be considered for use by clinicians to minimize white spot lesions.