bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of cadmium ion from wastewater by carbon-based nanosorbents: a review
Authors: Kumar Rajeev , Chawla Jyoti , Kaur Inderpreet
Published: February 2015

A green environment and a healthy life are dream projects of today's science and technology to save the world. Heavy metal ions in water affect both environment and human health. Cadmium has been identified as one of the heavy metals that causes acute or chronic toxic effects if ingested. Increasing use of cadmium in different technological fields has raised concern about its presence and removal from water/wastewater. Researchers have made many systematic efforts to remove heavy metals from water to reduce their impact on human beings and the environment. Adsorption is one of the best methods to remove heavy metals from water among the different proposed methods. This study explores carbon-based nanosorbents which have been proved as effective adsorbents for removal of cadmium ions from water. The adsorption efficiency of carbon-based nanosorbents is the main criterion to rank and select them for removal of cadmium ions from water. Toxicity, reusability and environmentally friendly characteristics of sorbents are also taken considered while ranking the suitable carbon-based nanosorbents for removal of cadmium ions from water.
Nosocomial pseudo-outbreak of Mycobacterium gordonae associated with a hospital's water supply contamination: a case series of 135 patients
Authors: Zlojtro Marija , Jankovic Mateja , Samarzija Miroslav , Zmak Ljiljana , Jankovic Vera Katalinic , Obrovac Mihaela , Zlojtro Igor , Jakopovic Marko
Published: February 2015

Nontuberculous mycobacteria (NTM) are opportunistic pathogens found in natural and human-engineered waters. In 2009, a relative increase in the isolation of Mycobacterium gordonae from pulmonary samples originating from General Hospital Zabok was noted by the National Mycobacteria Reference Laboratory. An epidemiological survey revealed a contamination of the cold tap water with M. gordonae and guidelines regarding sputum sample taking were issued. In addition, all incident cases of respiratory infection due to NTM reported from 2007 to 2012 at General Hospital Zabok were included in a retrospective review. Out of 150 individual NTM isolates, M. gordonae was the most frequently isolated species (n = 135; 90%) and none of the cases met the criteria of the American Thoracic Society for pulmonary NTM disease. While concomitant Mycobacterium tuberculosis infection was confirmed in only 6 (4%) patients, anti-tuberculosis treatment was initiated for a significant portion of patients (n = 64; 42.6%) and unnecessary contact tracing was performed. This study points out the need to enhance the knowledge about NTM in our country and indicates the importance of faster NTM identification, as well as the importance of good communication between laboratory personnel and physicians when evaluating the significance of the isolated NTM.
Cyclospora cayetanensis travels in tap water on Italian trains
Authors: Giangaspero A. , Marangi M. , Arace E.
Published: February 2015

Tap water samples from the toilets of an Italian national railway train were collected over a period of 10 months and tested for the presence of Cyclospora cayetanensis (C. cayetanensis) using EvaGreen® real-time polymerase chain reaction (RT-PCR) assay coupled with high resolution melting (HRM) analysis for protozoan detection and oocyst quantification. C. cayetanensis positive samples were detected in March, April, and May 2013, with the number of oocysts of 4, 5, and 11 per liter, respectively. This is the first finding of C. cayetanensis in water samples in Italy. The findings call for an improvement of hygiene and water safety by the Italian national railway company.
Evaluation of corrosion and scaling tendency indices in a drinking water distribution system: a case study of Bandar Abbas city, Iran
Authors: Alipour Vali , Dindarloo Kavoos , Mahvi Amir Hossein , Rezaei Leila
Published: February 2015

Corrosion and scaling is a major problem in water distribution systems, thus evaluation of water corrosivity properties is a routine test in water networks. To evaluate water stability in the Bandar Abbas water distribution system, the network was divided into 15 clusters and 45 samples were taken. Langelier, Ryznar, Puckorius, Larson–Skold (LS) and Aggressive indices were determined and compared to the marble test. The mean parameters included were pH (7.8 ± 0.1), electrical conductivity (1,083.9 ± 108.7 μS/cm), total dissolved solids (595.7 ± 54.7 mg/L), Cl (203.5 ± 18.7 mg/L), SO4 (174.7 ± 16.0 mg/L), alkalinity (134.5 ± 9.7 mg/L), total hardness (156.5 ± 9.3 mg/L), HCO3 (137.4 ± 13.0 mg/L) and calcium hardness (71.8 ± 4.3 mg/L). According to the Ryznar, Puckorius and Aggressive Indices, all samples were stable; based on the Langelier Index, 73% of samples were slightly corrosive and the rest were scale forming; according to the LS index, all samples were corrosive. Marble test results showed tested water of all 15 clusters tended to scale formation. Water in Bandar Abbas is slightly scale forming. The most appropriate indices for the network conditions are the Aggressive, Puckorius and Ryznar indices that were consistent with the marble test.
Characterization of bacterial pathogens in rural and urban irrigation water
Authors: Aijuka Matthew , Charimba George , Hugo Celia J. , Buys Elna M.
Published: February 2015

The study aimed to compare the bacteriological quality of an urban and rural irrigation water source. Bacterial counts, characterization, identification and diversity of aerobic bacteria were determined. Escherichia coli isolated from both sites was subjected to antibiotic susceptibility testing, virulence gene (Stx1/Stx2 and eae) determination and (GTG)5 Rep-PCR fingerprinting. Low mean monthly counts for aerobic spore formers, anaerobic spore formers and Staphylococcus aureus were noted although occasional spikes were observed. The most prevalent bacterial species at both sites were Bacillus spp., E. coli and Enterobacter spp. In addition, E. coli and Bacillus spp. were most prevalent in winter and summer respectively. Resistance to at least one antibiotic was 84% (rural) and 83% (urban). Highest resistance at both sites was to cephalothin and ampicillin. Prevalence of E. coli possessing at least one virulence gene (Stx1/Stx2 and eae) was 15% (rural) and 42% (urban). All (rural) and 80% (urban) of E. coli possessing virulence genes showed antibiotic resistance. Complete genetic relatedness (100%) was shown by 47% of rural and 67% of urban E. coli isolates. Results from this study show that surface irrigation water sources regardless of geographical location and surrounding land-use practices can be reservoirs of similar bacterial pathogens.
The reception of nineteenth-century Serbian salon music: Performer, audience and music critic perspectives
Authors: Kokanovic-Markovic Marijana
Published: February 2015

The history of Salon Music can be traced through the tense, dynamic relation
between the consumers of that kind of music (performers, listeners) and
critics. In the early 1930s, and later even more, a designation ?salon style?
started to appear in the reviews of the Salon Music. By that fact alone, it
was implied that compositions, which were published as Salon Music, or were
defined as such in reviews, corresponded to specific musical norms, which, on
the other hand, evolved merely from recipient?s needs. In foreign and
domestic press from the period, there are many negative epithets referring to
Salon Music: ?empty, frivolous, coquette, false?. Nevertheless, aesthetic
debates in music literature had no impact on Salon Music admirers. In this
study, the focus of attention is on the reception of Serbian Salon Music of
the nineteenth century within the context of the Central European cultural
practice. Salon compositions were interpreted within the interactive
relations among musical work-performers-audience-critics. The goal of musical
work analysis was not to evaluate the artistic quality or non-quality of the
Salon Music, in order to distinguish more or less successful music
compositions. It is far more important to bear in mind that artistic quality
with the Salon Music consumers of the time had no decisive role. Musical work
analysis no longer seeks for aesthetical values in music facts, but for
qualities and features that a piece of music must possess in order to fulfill
its purpose and function.
Writers and chanters in the nineteenth century as keepers of the tradition of Serbian church music
Authors: Marjanovic Natasa
Published: February 2015

In this paper, parts of the memoir literary works from the second half of the
nineteenth century are presented as important sources for the research of
Serbian traditional church chant. The testimonies on church music from
diaries, memoirs and autobiographical notes by famous Serbian writers,
statesmen and politicians, namely Jovan Subotic, Jakov Ignjatovic, Milan
Savic, Milica Stojadinovic Srpkinja, Todor Stefanovic Vilovski, Vladimir
Jovanovic and Kosta Hristic, were analyzed. Those writings bring to light a
time when church chant was appreciated as an important part of the spiritual,
folk heritage and had an important role in everyday culture of Serbian people
both in the Habsburg Monarchy and in the Principality and Kingdom of Serbia.
The authors wrote about musical skills of chanters from clerical, church
circles and about the practice of chanting among school teachers. They also
described different kinds of musical performances of church chant among
laymen and children. These sources testify to writers? general and musical
education and experiences, to their environment and its relation to the
aesthetics of spiritual folk tradition. This paper also analyzes sources in
the context of the history and theory of literature, having in mind the
authors? commentary techniques and narrative style. Those issues are
discussed in relation to the poetics of romanticism, Biedermeier and realism
in Serbian literature.
On the multipart singing in the religious practice of orthodox Greeks and Serbs: The theological-culturological discourse
Authors: Peno Vesna
Published: February 2015

In 1844, Serbian patriarch Josif Rajacic served two central annual Liturgies,
at the feasts of Pasha and Penticost, in the Greek church of Holy Trinity in
Vienna; these were accompanied by the four-part choral music. The appearance
of new music in several orthodox temples in Habsburg Monarchy (including this
one) during the first half of the nineteenth century, became an additional
problem in a long chain of troubles that had disturbed the ever imperiled
relations between the local churches in Balkans, especially the Greek and
Serbian Orthodox. The official epistle that was sent from the ecomenical
throne to all sister orthodox churches, with the main request to halt this
strange and untraditional musical practice, provoked reactions from Serbian
spiritual leader, who actually blessed the introduction of polyphonic music,
and the members of Greek parish at the church of St. George in Vienna, who
were also involved with it. The correspondence between Vienna and
Constantinople reflected two opposite perceptions. The first one could named
?traditional? and the other one ?enlightening?, because of the apologies for
the musical reform based on the unequivocal ideology of Enlightenment. In
this article the pro et contra arguments for the new music tendencies in
Greek and Serbian orthodox churches are analyzed mainly from the viewpoint of
the theological discourse, including the two phenomena that seriously
endangered the very entity of Orthodox faith. The first phenomenon is the
ethnophiletism which, from the Byzantine era to the modern age, was gradually
dividing the unique and single body of Orthodox church into the so-called
?national? churches, guided by their own, almost political interests, often
at odds with the interests of other sister churches. The second phenomenon is
the Westernization of the ?Orthodox soul? that came as a sad result of
countless efforts of orthodox theological leaders to defend the Orthodox
independence from the aggressive Roman Catholic proselytism. ?The Babylonian
captivity of the Orthodox church?, as Georg Florovsky used to say, began when
Orthodox theologians started to apply the Western theological methods and
approaches in their safeguarding of the Orthodox faith and especially in
ecclesiastical education. In this way the new cultural and social tendencies
which gripped Europe after the movements of Reformation and
Contra-Reformation were adopted without critical thinking among Orthodox
nations, especially among the representatives of the Ortodox diaspora at the
West. Observed from this extensive context, the four-part music in Orthodox
churces in Austria shows one of many diverse requirements demanded from the
people living in a foreign land, in an alien and often hostile environment,
to assimilate its values, in this case related to the adoption of its musical
practices.
Two views on the Yugoslav ideology in Serbian music periodicals between the two world wars
Authors: Vasic Aleksandar
Published: February 2015

This study explores the relationship between the Yugoslav ideology as
exhibited in Serbian music magazines published between the two world wars.
These are the following journals: Music (1928-1929), Bulletin of the Music
Society ?Stankovic? (1928-1934, 1938-1941; in January 1931 it was renamed The
Musical Gazette), The Sound (1932-1936), Herald of the South Slavic Choral
Union (1935-1936, 1938), Slavic music (1939-1941) and Review of Music (1940).
I have excluded the magazine Musical Gazette (1922) from consideration
because I have already discussed its ideological aspects in an earlier
article (2009). Yugoslav topics in interwar music periodicals are addressed
in an ecstatic tone by the music writers and editors (particularly
immediately after the foundation of the Kingdom of Serbs, Croats and
Slovenes); one also observes open dissent and criticism of undesirable,
wasted tendencies. Signs of profound differences with respect to the
fundamental aspect of Yugoslav ideology - i.e. on the question of the nature
and degree of the unity of nations under the auspices of the ideology,
appeared relatively early in these journals. I argue that three elements:
open enthusiasm, criticism/polemic and fundamental differences, constituted a
framework within which the Yugoslav ideology was expressed in the Serbian
musical periodicals. The third aspect has proved to be crucial. One could
observe two different and even opposing views on the Yugoslav ideology. While
some musicians strongly advocated integral Yugoslavism, others wanted the
preservation of distinctive national features within this ideology. This
division is illustrated by the writings of Croatian composer and
ethnomusicologist Bozidar Sirola and Serbian composer and music critic
Milenko Zivkovic. The division in question culminated in the case of the
South Slavic Choral Union, which Croatian Choral Union refused to join.
Hence, Serbian music periodicals provide an insight into the fundamental
ideological and political problem of the Kingdom of Yugoslavia.
Institutionalization of ethnochoreology in Serbia: The legacy of Ljubica Jankovic at the Institute of musicology SASA
Authors: Dumnic Marija , Lajic-Mihajlovic Danka
Published: February 2015

Since 1964, the Institute of Musicology of the Serbian Academy of Sciences
and Arts has been cherishing the official archive of the academician Ljubica
Jankovic, ethnochoreologist, which originates from her service at the
Ethnographic Museum in Belgrade (1939-1951). The legacy contains
documentation about the activity of the Folk Dance Section of the
Ethnographic Museum in Belgrade, and extensive data on folk dances in
Yugoslavia from the first half of the twentieth century. This paper presents
part of the archival documentation relating to the establishment and activity
of the Folk Dance Section. It was the first state institution to collect
primary and secondary research sources relating to folk dance structure and
to the social context of a rural dance practice. Apart from that, it was the
institution for education on folk dance preservation and staging. The focus
of the paper is on the fundamental documents of ethnochoreological cultural
and research policy in Serbia, manuscripts The Draft for Work at the Folk
Dance Section of the Ethnographic Museum in Belgrade [Nacrt za rad u Otseku
narodnih igara pri Etnografskom muzeju u Beogradu] (1939) and The Program for
Work at the Department for Intangible Culture with the Sections: 1) Folk
Dances and Folk Music; 2) Folk Literature; 3) Folk Art and Ornamentation; 4)
Folk Customs and Religion; 5) Folk Medicine [Program rada u Odeljenju za
duhovnu kulturu sa Otsecima: 1) za narodne igre i narodnu muziku; 2) za
narodnu knjizevnost; 3) za narodnu likovnu umetnost i ornamentiku; 4) za
narodne obicaje i veru; 5) za narodnu medicinu] (1946). The aim of this study
is to contribute to the history of ethnochoreology in Serbia by introducing
the ideas of Ljubica Jankovic concerning folk dance research and preservation
strategies because of their importance for the interpretation of numerous
ethnochoreological and ethnomusicological theoretical and analytical results,
mostly achieved in cooperation with her sister, Danica Jankovic. In addition,
we indicate the applicability of the first official ethnochoreological ideas
for current folk dance research in Serbia.
Big Data as Complementary Audit Evidence
Authors: Yoon Kyunghee , Hoogduin Lucas , Zhang Li
Published: February 2015

SYNOPSIS

In this paper we argue for the use of Big Data as complementary audit evidence. We evaluate the applicability of Big Data using the audit evidence criteria framework and provide cost-benefit analysis for sufficiency, reliability, and relevance considerations. Critical challenges, including integration with traditional audit evidence, information transfer issues, and information privacy protection, are discussed and possible solutions are provided.
In vitro evaluation of microbial contamination of orthodontic brackets as received from the manufacturer using microbiological and molecular tests
Authors: dos Santos Gerzson Darlene R. , Simon Daniel , dos Anjos Aline Lima , Freitas Maria Perpétua Mota
Published: February 2015

Objective: 

To test the null hypothesis that orthodontic brackets as supplied by manufacturers do not have microbial contamination.

Materials and Methods: 

The sample comprised 140 brackets of four different commercially available brands, used directly from the manufacturer's packaging, divided into 14 groups (n  =  10 brackets each). Of the 140 pieces, 60 were full cases and 80 were replacement brackets. Materials were tested to detect bacterial growth, analyze types of bacteria present (biochemical test), and identify bacteria (molecular test with polymerase chain reaction [PCR]).

Results: 

In two of 12 groups the brackets showed microbial contamination: group 1, Morelli full case brackets, and group 12, Abzil-3M Unitek replacement brackets. Staphylococcus aureus and Staphylococcus epidermidis were the bacteria identified in groups 1 and 12, respectively (suggested by the biochemical test and confirmed by PCR).

Conclusions: 

Brackets of two brands (Morelli and Abzil-3M Unitek) were found to be contaminated by bacteria in the original packages supplied by the manufacturers, which suggests a risk for patient contamination. These data suggest that the manufacturers of these materials should improve the quality control of the packaging used, including sterilization, for the security of patient health.
Epigenetic Regulation of Placenta-Specific 8 Contributes to Altered Function of Endothelial Colony-Forming Cells Exposed to Intrauterine Gestational Diabetes Mellitus
Authors: Blue Emily K. , Sheehan BreAnn M. , Nuss Zia V. , Boyle Frances A. , Hocutt Caleb M. , Gohn Cassandra R. , Varberg Kaela M. , McClintick Jeanette N. , Haneline Laura S.
Published: February 2015

Intrauterine exposure to gestational diabetes mellitus (GDM) is linked to development of hypertension, obesity, and type 2 diabetes in children. Our previous studies determined that endothelial colony-forming cells (ECFCs) from neonates exposed to GDM exhibit impaired function. The current goals were to identify aberrantly expressed genes that contribute to impaired function of GDM-exposed ECFCs and to evaluate for evidence of altered epigenetic regulation of gene expression. Genome-wide mRNA expression analysis was conducted on ECFCs from control and GDM pregnancies. Candidate genes were validated by quantitative RT-PCR and Western blotting. Bisulfite sequencing evaluated DNA methylation of placenta-specific 8 (PLAC8). Proliferation and senescence assays of ECFCs transfected with siRNA to knockdown PLAC8 were performed to determine functional impact. Thirty-eight genes were differentially expressed between control and GDM-exposed ECFCs. PLAC8 was highly expressed in GDM-exposed ECFCs, and PLAC8 expression correlated with maternal hyperglycemia. Methylation status of 17 CpG sites in PLAC8 negatively correlated with mRNA expression. Knockdown of PLAC8 in GDM-exposed ECFCs improved proliferation and senescence defects. This study provides strong evidence in neonatal endothelial progenitor cells that GDM exposure in utero leads to altered gene expression and DNA methylation, suggesting the possibility of altered epigenetic regulation.
Experimental approach for quantification of fluid dynamics in laser metal welding
Authors: Tenner Felix , Berg Benjamin , Brock Christian , Klämpfl Florian , Schmidt Michael
Published: February 2015

Laser metal welding is widely applied in industry. Nevertheless, a complete process understanding which leads to a full control of the process is not available yet. To contribute a solution for this task, we use two high-speed cameras with recording rates of up to 250 kHz and measure the velocity and direction of the fluid flow inside the keyhole with very high precision. Furthermore, we use tracer particles to measure the fluid dynamics in the keyhole. To get a deep view into the keyhole without the use of x-rays, we use a setup which allows us to look inside the keyhole during overlap welding of zinc-coated steel sheets with a spatial resolution of 25 μm per pixel and a temporal resolution of 5.3 μs per frame. Moreover, we quantify the influence of this approach on the process dynamics. Our findings show how the fluid dynamics inside the keyhole are linked to the laser power, the feed rate, and a gap between two zinc-coated steel sheets.
Laser surface pre-treatment of aluminum for hybrid joints with glass fiber reinforced thermoplastics
Authors: Heckert André , Zaeh Michael F.
Published: February 2015

Lightweight construction is a major trend in the automotive industry. The connection of fiber reinforced plastics with aluminum is consequently seen as a promising prospect. In this regard, thermal joining is one potential joining technology for bonding of such hybrid joints. Yet a pretreatment of the aluminum surface is necessary to create a load bearing metal-plastic joint. Recent research has shown that a laser surface pretreatment provides high joint strengths. However, there is a variety of laser sources and possible surface topographies with typical structure sizes ranging from macroscopic to nanoscopic profiles. Within this work, two different laser induced structures were generated on aluminum sheets which were subsequently joined to glass fiber reinforced thermoplastics. One of the two laser structures was created with a continuous wave laser using a modified remote ablation cutting process. The other structure was manufactured by a pulsed laser source with a pulse width in the nanosecond-range. The two laser processes were compared with a conventional abrasive blasting process and they were characterized in terms of surface topography and chemical composition of the surface. Furthermore, the achievable joint strength for joining with glass fiber reinforced thermoplastics was investigated. It is shown that the properties of the thermoplastic as well as the surface topography and chemical composition of the metal strongly influence the resulting joint strength.
Laser and laser gas-metal-arc hybrid welding of 960 MPa direct-quenched structural steel in a butt joint configuration
Authors: Siltanen Jukka , Tihinen Sakari , Kömi Jukka
Published: February 2015

Welding trials have been carried out using direct-quenched 960 MPa ultrahigh-strength steel utilizing several welding processes: gas-metal-arc, laser, and laser gas-metal-arc hybrid welding. Laser power sources like the CO2-laser and the fiber-delivered solid state laser were used. In the trials, butt joints with various groove geometries were used and the thickness of the base material was a constant 6 mm. Welding filler materials varied from matching Union X96 (ISO 14341: G 89 5 M Mn4Ni2.5CrMo) to undermatching Esab OK 12.50 (G3Si1). The diameter of the filler wire varied from 1 to 1.2 mm. The highest hardness value, over 400 HV, was reached on laser welds. According to the results, the strength of the joints corresponded to the nominal strength of base materials (tensile strength of 960 MPa), regardless of the welding method and welding filler material used. As a whole, the results of transverse bend testing were poor as expected, especially when the face side of welds was under tension. The standardized bend and also the used impact toughness tests (Charpy-V) are not the best methods to evaluate the ductility or the toughness of a weld in direct-quenched steels. However, relatively good impact toughness values were achieved to the fusion line of the welds both with the continuous laser and laser hybrid welding process, reaching 57 J with the laser welding and 49 J with the laser hybrid welding when the matching filler material was used.
Surface structuring by remelting of titanium alloy Ti6Al4V
Authors: Temmler A. , Walochnik M. A. , Willenborg E. , Wissenbach K.
Published: February 2015

Conventional surface structuring processes often share two crucial disadvantages. First, after the structuring process itself, some kind of surface finishing is often needed, based on another technology, which means a substantial additional expense. Second, all conventional surface structuring processes are based on the removal of material, which is wasted without any further use during processing. A new approach of structuring metallic surface structuring by laser remelting (WaveShape). In this process, no material is removed but reallocated while molten. This structuring process is based on the new active principle of remelting. The surface structure and the microroughness result from a laser-controlled self-organization of the melt pool due to surface tension. Up to now, basic research has been focused on hot work steel 1.2343 (AISI: H11), and promising results have been achieved for this material. Current research and development are now seeking to expand the spectrum of processable materials. Since remelting is a thermally driven process, significant differences between metallic materials are expected due to their thermo physical properties such as thermal conductivity, absorption coefficient, viscosity, and heat capacity. The titanium alloy Ti6Al4V has a wide range of industrial applications, especially for aviation, aerospace, and medical engineering. The WaveShape process for this material will be investigated within this paper. The procedural principle of surface structuring by remelting is based upon a sinusoidal modulation of laser power while the laser beam is moved over the surface. The lower process limit of laser power is the power required to melt material and, therefore, create a melt pool. In this context, the upper process limit of laser power is the point just before substantial amounts of the molten material are evaporated. We used metallographic cross sections to measure the dimensions of melt pool depth and width as they depend on procedural parameters, such as laser beam diameter (125–500 μm), scanning velocity (25–200 mm/s), and laser power (20–400 W). We also investigated basic interdependencies between structural characteristics (e.g., height) and procedural parameters used, such as laser beam diameter, laser power, and wavelength of modulation. The results show that the WaveShape process is well suited to process titanium alloy Ti6Al4V since structures and process velocities achieved are significantly higher than for the previously investigated hot work steel.
Selective laser melting of aluminum die-cast alloy—Correlations between process parameters, solidification conditions, and resulting mechanical properties
Authors: Buchbinder D. , Meiners W. , Wissenbach K. , Poprawe R.
Published: February 2015

The additive production technology selective laser melting (SLM) is used for direct fabrication of metal-based functional components. SLM is one of the powder-bed based AM technologies. SLM is well established in serial production for dental restoration as well as for tooling. Main concern for industrial application remains the scope of processible materials and resulting mechanical properties. Toward processing of aluminum alloys commercially available systems exist with comparability in terms of applied process parameters and resulting mechanical properties remaining a challenge. Often no data are available concerning process parameters and mechanical properties. This holds especially for high-power SLM systems with increased build rates as a result of extended laser powers of up to 1 kW. Especially when processing aluminum alloys, the solidification conditions significantly affect the resulting microstructure in terms of size of dendrites and grains. Consequently, the present paper systematically investigates and correlates the process parameters (e.g., laser power, scan speed, layer orientation, preheating, etc.) on the microstructure (electron backscatter diffraction and texture) and resultant mechanical properties (hardness, tensile strength, yield strength, and breaking elongation) for aluminum die-cast alloys. At this, underlying phenomena for typically observed anisotropy of mechanical properties in dependence on layer orientation are further specified.
Laser transmission welding of carbon fiber reinforced thermoplastic using filler material—A fundamental study
Authors: Berger Stefan , Oefele Florian , Schmidt Michael
Published: February 2015

In the automotive industry, the increasing environmental awareness is reflected through consistent lightweight construction. Especially, the use of carbon fiber reinforced thermoplastic plays an increasingly important role. Accordingly, to the material substitution, the demand for adequate joining technologies is growing. Therefore, laser transmission welding using filler material provides a way to combine two opaque joining partners by using the process specific advantages of the laser transmission welding process. After introducing the new joining technology and the applied experimental setup, this paper will investigate the process itself and the conditions for a stable process. Fundamental studies of the absorption characteristics of the applied carbon reinforced thermoplastic and the heat distribution within the surface due to laser impact are performed. To analyze the resulting weld seam quality and to investigate the influence on the process parameters and the welding process itself, lap shear tests are carried out. After all, a thermal model for the joining process is generated and presented in this paper.
Rapid laser sintering of alkaline fuel cell substrates using integrating mirror
Authors: Garibay Jorge Paredes , Kaakkunen Jarno J. J. , Penttilä Raimo , Harris Jennifer , McIntyre John , Laakso Petri , Kujanpää Veli
Published: February 2015

Nickel screens and foams are commonly used in alkaline fuel cell (AFC) as substrates to support electrodes. The methods used for fabrication of these substrates impact significantly on the viability, with the material and processing cost of nickel comprising almost one third of the total. Therefore, improvements to the manufacturing speed of substrates would increase affordability. Currently, state of the art commercial selective laser sintering systems are limited to a volumetric manufacturing speed of 1–3 mm3/s. This study describes a novel technique that multiplies the sintering speed of nickel AFC substrates. The novel technique is based on an integrating mirror, which creates a homogenized 60 mm wide and 0.3 mm long beam from a Nd:YAG laser, and a 0.8 mm thick nickel powder layer in a nitrogen environment. The influence of the nickel powder characteristics, and sintering parameters, as velocity, laser power, etc., and postsintering treatments of the samples on the mechanical properties of the substrates were studied. Based on experimental results, the sintering speed could be multiplied up to a factor of 150 compared to the standard laser sintering speed. Additionally, because structure of the substrate has a significant impact on cell performance, a case study was defined to present the performance and characteristics of the sintered substrates on AFCs. Laser sintered substrates show promise, exhibiting a small performance drop of less than 25 mV (about 7%) compared to the in-house standard.
Numerical sensitivity analysis of single pulse laser welding with a C-shaped beam
Authors: Sundqvist Jesper , Kaplan Alexander F. H. , Yen Kong Choon , Assuncao Eurico , Quintino Luisa , Blackburn Jon
Published: February 2015

Even though Gaussian and top-hat beam profiles are suitable for most laser welding applications, for certain cases other beam distributions can be favored in terms of weld quality or performance. One promising method to generate a tailored beam shape is diffractive optical elements. A numerical model on the temperature field generated by specific beam shapes is therefore under development to iteratively identify desired beam shapes for specific applications. The present study is based on two thin steel sheets that are conduction welded in a lap joint mode by a C-shaped single laser pulse. The main aim is to ensure a specified weld width along the C-weld shape at the overlap interface between the two sheets in a robust manner. The sensitivity of main criteria like the interface weld width and phase changes at the workpiece top and bottom is studied and discussed in a systematic manner by applying a numerical heat transfer model for various parameters and conditions.
Numerical modeling and characterization of the laser–matter interaction during high-power continuous wave laser perforation of thin metal plates
Authors: Horak Johannes , Heunoske Dominic , Lueck Martin , Osterholz Jens , Wickert Matthias
Published: February 2015

The phenomena occurring during laser–metal interaction depend on a variety of parameters such as laser wavelength, intensity, and thermophysical and optical properties of the irradiated material. This work comprises a detailed study of the perforation process of thin iron and steel plates under CW laser radiation at a wavelength of 1.07 μm. Experiments were carried out over a wide range of intensities between 0.1 and 100 kW/cm2, and with beam radii in the millimeter and centimeter range. Additionally, we describe a method applying contact-free radiative temperature measurements, which allows the measurement of melt-through times without an exact knowledge of the plate's spectral surface emissivity. A detailed numerical model is presented and employed to analyze, interpret, and predict data gathered from the experiments. The model is shown to produce accurate predictions and is in good agreement with experimental data. Furthermore, our results indicate that in the investigated regime perforation is governed by gravitational and surface forces. Based on this hypothesis, a criterion for the onset of the perforation explaining the observed local minimum in the perforation time versus beam radius curve is presented.
Minimization of distortions during laser welding of ultra high strength steel
Authors: Fahlström Karl , Andersson Oscar , Todal Urban , Melander Arne
Published: February 2015

Ultra high strength steels are frequently used within the automotive industry for several components. Welding of these components is traditionally done by resistance spot welding, but to get further productivity and increased strength, laser welding has been introduced in the past decades. Fusion welding is known to cause distortions due to built in stresses in the material. The distortions result in geometrical issues during assembly which become the origin of low joint quality due to gaps and misfits. U-beam structures of boron steel simulating B-pillars have been welded with laser along the flanges. Welding parameters and clamping have been varied to create different welding sequences and heat input generating a range of distortion levels. The distortions have been recorded dynamically with an optical measurement system during welding. In addition, final distortions have been measured by a digital Vernier caliper. The combined measurements give the possibility to evaluate development, occurrence, and magnitude of distortions with high accuracy. Furthermore, section cuts have been analyzed to assess joint geometry and metallurgy. The results show that final distortions appear in the range of 0–8 mm. Distortions occur mainly transversely and vertically along the profile. Variations in heat input show clear correlation with the magnitude of distortions and level of joint quality. A higher heat input in general generates a higher level of distortion with the same clamping conditions. Section cuts show that weld width and penetration are significantly affected by welding heat input. The present study identifies parameters which significantly influence the magnitude and distribution of distortions. Also, effective measures to minimize distortions and maintain or improve joint quality have been proposed. Finally, transient finite element (FE) simulations have been presented which show the behavior of the profiles during the welding and unclamping process.
High-rate laser microprocessing using a polygon scanner system
Authors: Loeschner Udo , Schille Joerg , Streek Andre , Knebel Tommy , Hartwig Lars , Hillmann Robert , Endisch Christian
Published: February 2015

This paper discusses results obtained in high-rate laser microprocessing by using a high average power high-pulse repetition frequency ultrashort pulse laser source in combination with an in-house developed polygon scanner system. With the recent development of ultrashort pulse laser systems supplying high average power of hundreds watts and megahertz pulse repetition rates, a significant increase of the productivity can potentially be achieved in micromachining. This permits upscaling of the ablation rates and large-area processing, gaining increased interest of the ultrashort pulse laser technology for a large variety of industrial processes. However, effective implementation of high average power lasers in microprocessing requires fast deflection of the laser beam. For this, high-rate laser processing by using polygon scanner systems provide a sustainable technological solution. In this study, a picosecond laser system with a maximum average power of 100 W and a repetition rate up to 20 MHz was used. In raster scanning using the polygon scanner, the laser beam with a focus spot diameter of 44 μm was deflected with scan speeds of several hundred meters per second. The two-dimensional scanning capability of the polygon scanner supplied a scan field of 325 × 325 mm. The investigations were focused on high-rate large-area laser ablation of technical grade stainless steel as well as selective thin film ablation from bulk substrates. By variation of the processing parameters laser fluence, as well as temporal and spatial pulse-to-pulse distance, their impact onto the ablation process was evaluated with respect to the ablation rate, processing rate, surface quality, and ablation efficiency.
New approach to clamping in microwelding
Authors: Patschger Andreas , Hopf Andreas , Loose Tobias , Bliedtner Jens , Bergmann Jean Pierre
Published: February 2015

For the purpose of manufacturing lithium ion cells, microwelding is a commonly used procedure. It is also applied to new products as vacuum insulation elements which are enclosed in stainless steel foils. Another new application can be found in welding of catalytic converters. Before, they were usually joined by furnace brazing. All these products consist of thin metal foils which can be considered two-dimensional work pieces. They have to be joined in a stable process in order to avoid rejects. One of the biggest challenges in thermal microwelding is the gap forming between the join partners due to thermally induced distortion. In microwelding, the possibility to bridge the gap between the join partners is ensured as long as the gap is smaller than approximately half of the material thickness. Beyond this point, weld seam imperfections occur and the process collapses. In order to minimize gap formation, a new approach to clamping is presented which directly applies the clamping force in the welding zone. Based on this invention, a clamping fixture was constructed and qualified. Thereby, it is possible to close the gap between join partners and adapt the properties of lap joints to bead-on-plate welds. Furthermore, the new concept was compared to a common clamping fixture. Thus, weldable join partner thickness could be reduced, and the feeding rate was extended.
Comparative study of numerical models of the laser forming process
Authors: Torres Cruz Alberto , de Lange Dirk F. , Medellín Castillo Hugo I.
Published: February 2015

Even though the laser forming process is not used at a large scale, it has a potential value for small product series. Its advantage is in its capacity to deform a sheet into arbitrary shapes by a contact-free laser irradiation, avoiding the need for costly tools in which materials need to be formed in arbitrary shapes. One of the reasons that the process has not become very popular is by the difficulty to predict and control the process and determine the right processing plan to obtain the shape needed. The simulation of the laser forming process is not easy to carry out, because the nature of the problem is three-dimensional and the process is transient. In addition, the description of the material behavior, which includes thermo-elastoplastic behavior, is complex and results in strongly nonlinear problems. Moreover, the temperature dependent material behavior, including the microstructural evolution of the material is often not known to a sufficient degree of precision, which leads to approximate descriptions. For that reason, in the current study a simple application, bending of a flat plate by irradiation over a straight line, is studied by a range of models with a varying degree of complexity. The models are compared in order to evaluate if a simplified model can be used to obtain adequate numerical results under particular conditions. Simplifications can be the reduction of the moving point heat source to a fixed but transient line heat source over the complete trajectory, or reducing the 3D model to a 2D model. From the analysis, it becomes clear that the effects of all three dimensions and the heat source movement are relevant for the ultimate precision of the simulation results, and to obtain the correct tendencies of the effect of changes of some of the parameters on the process results. Nevertheless, the results also demonstrate that some relevant thermal and stress data can be obtained using simplified models at a considerably lower computational cost. In particular, the thermal data are less affected by model simplifications, whereas the stress and deformation fields are more sensitive to the model approximations. An improved 2D model is proposed and evaluated, which is able to take into account the effect of the moving point heat source, while ignoring the longitudinal dimension.
Mapping of polar fox renal cortex proteins using two-dimensional gel electrophoresis and mass spectrometry – a preliminary study
Authors: Ciechanowicz A.K. , Ożgo M. , Stański Ł.R. , Herosimczyk A. , Piotrowska A. , Szymeczko R. , Laszczyńska M. , Skrzypczak W.F.
Published: February 2015

The aim of the present study was to establish protein map of polar fox (Alopex lagopus) renal cortex. Kidney cortex proteins of isoelectric point ranging from 3 to 10 were analysed using two-dimensional electrophoresis and MALDI-TOF mass spectrometry. Sixteen protein spots corresponding to thirteen different gene products were identified. These proteins were divided into following groups: lipid and fatty acid metabolism, amino acid metabolism, energetic pathways, regulatory proteins, transport proteins and structural proteins. This is the first attempt to create reproducible 2-D map, of renal cortex proteins characteristic for polar foxes, used as animal model for carnivores. It is worth emphasizing that the results of this study may broaden currently available protein databases
Quantitative PCR High-Resolution Melting (qPCR-HRM) curve analysis, a new approach to rapid detection and differentiation of bovine papillomavirus detected in equine sarcoids
Authors: Szczerba-Turek A. , Bancerz-Kisiel A. , Lipczyńska K. , Siemionek J. , Raś A. , Platt-Samoraj A. , Szweda W.
Published: February 2015

The aim of the study was to evaluate a novel diagnostic scheme which combines quantitative PCR and High-Resolution Melting (qPCR-HRM) curve analysis for rapid differentiation based on E5 partial CDS of bovine papillomavirus type 1 or 2 (BPV-1 or BPV-2), and to perform a phylogenetic analysis of the complete CDS of the E5 gene of BPV detected in equine sarcoids. Samples of 38 skin lesions obtained from 27 horses were collected for molecular examinations. All lesions were clinically diagnosed as sarcoids, but results of histopathological examinations did not always corroborate the clinical diagnosis. Although all the samples were positive for the presence of BPV DNA, after qPCR-HRM analysis 6 (16%) specimens were recognized as BPV-1 “wild”, 24 (63%) as BPV-1 “European” and 8 (21%) as a “variant” of BPV E5 ORF partial CDS. Phylogenetic analysis based on nucleotide sequences of E2 ORF partial CDS and E5 ORF complete CDS was conducted on 7 specimens, whose sequences were published in GenBank and recognized as: 2PL (Accession Number - Acc. No. KC684939) - “variant” BPV-1, 7aPL (Acc. No. KC684940) - “European” BPV-1, 10PL (Acc. No. KC693480) - “variant” BPV-1, 16PL (Acc. No. KC693484) - “variant” BPV-2, 17PL (Acc. No. KC693481) - “variant” BPV-1, 20aPL (Acc. No. KC693482) - “European” BPV-1 and 20cPL (Acc. No. KC693483) - “wild” BPV-1. Amino acid (aa) sequences of E5 ORF complete CDS were also analyzed. The E5 variant of aa sequences found in isolate 10PL (protein identification - ID: AGM 20700) is a novel variant of E5 ORF complete CDS of BPV-1 detected in equine sarcoid in Poland