bluuebunny/crossref_metadata_2025 huggingface dataset:
Therapeutic Potential of Plants as Anti‐Microbials for Drug Discovery
Authors: Perumal Samy Ramar , Gopalakrishnakone Ponnampalam
Published: June 2008

The uses of traditional medicinal plants for primary health care have steadily increased worldwide in recent years. Scientists are in search of new phytochemicals that could be developed as useful anti‐microbials for treatment of infectious diseases. Currently, out of 80% of pharmaceuticals derived from plants, very few are now being used as anti‐microbials. Plants are rich in a wide variety of secondary metabolites that have found anti‐microbial properties. This review highlights the current status of traditional medicine, its contribution to modern medicine, recent trends in the evaluation of anti‐microbials with a special emphasis upon some tribal medicine, in vitro and in vivo experimental design for screening, and therapeutic efficacy in safety and human clinical trails for commercial outlet. Many of these commercially available compounds are crude preparations administered without performing human clinical trials. Recent methods are useful to standardize the extraction for scientific investigation of new phytochemicals and anti‐microbials of traditionally used plants. It is concluded that once the local ethnomedical preparations of traditional sources are scientifically evaluated before dispensing they should replace existing drugs commonly used for the therapeutic treatment of infection. This method should be put into practice for future investigations in the field of ethnopharmacology, phytochemistry, ethnobotany and other biological fields for drug discovery.
Evidence of disassortative mating in a Tanganyikan cichlid fish and its role in the maintenance of intrapopulation dimorphism
Authors: Takahashi Tetsumi , Hori Michio
Published: June 2008

Morphological dimorphism in the mouth-opening direction (‘lefty’ versus ‘righty’) has been documented in several fish species. It has been suggested that this deflection is heritable in a Mendelian one-locus, two-allele fashion. Several population models have demonstrated that lateral dimorphism is maintained by negative frequency-dependent selection, resulting from interactions between predator and prey species. However, other mechanisms for the maintenance of lateral dimorphism have not yet been tested. Here, we found that the scale-eating cichlid fish
Perissodus microlepis
exhibited disassortative mating, in which reproductive pairings between lefties and righties occurred at higher than expected frequency (
p
<0.001). A previous study reported that a lefty–righty pairing produces a 1 : 1 ratio of lefty : righty young, suggesting that disassortative mating contributes to the maintenance of lateral dimorphism. A combination of disassortative mating and negative frequency-dependent selection may stabilize lateral dimorphism more than would a single mechanism.
Autosomal variation for male body size and sperm competition phenotypes is uncorrelated in
Drosophila melanogaster
Authors: Zhang Rui , Amah Linda , Fiumera Anthony C
Published: June 2008

Correlations between male body size and phenotypes impacting post-copulatory sexual selection are commonly observed during the manipulation of male body size by environmental rearing conditions. Here, we control for environmental influences and test for genetic correlations between natural variation in male body size and phenotypes affecting post-copulatory sexual selection in
Drosophila melanogaster
. Dry weights of virgin males from 90 second-chromosome and 88 third-chromosome substitution lines were measured. Highly significant line effects (
p
<0.001) documented a genetic basis to variation in male body size. No significant correlations were identified between male body size and the components of sperm competitive ability. These results suggest that natural autosomal variation for male body size has little impact on post-copulatory sexual selection. If genetic correlations exist between male body size and post-copulatory sexual selection then variation in the sex chromosomes are likely candidates, as might be expected if sexually antagonistic coevolution was responsible.
Computational complexity with experiments as oracles
Authors: Beggs Edwin , Costa José Félix , Loff Bruno , Tucker John V
Published: June 2008

We discuss combining physical experiments with machine computations and introduce a form of analogue–digital (AD) Turing machine. We examine in detail a case study where an experimental procedure based on Newtonian kinematics is combined with a class of Turing machines. Three forms of AD machine are studied, in which physical parameters can be set exactly and approximately. Using non-uniform complexity theory, and some probability, we prove theorems that show that these machines can compute more than classical Turing machines.
Species–specific interactions between algal endosymbionts and coral hosts define their bleaching response to heat and light stress
Authors: Abrego David , Ulstrup Karin E , Willis Bette L , van Oppen Madeleine J.H
Published: June 2008

The impacts of warming seas on the frequency and severity of bleaching events are well documented, but the potential for different
Symbiodinium
types to enhance the physiological tolerance of reef corals is not well understood. Here we compare the functionality and physiological properties of juvenile corals when experimentally infected with one of two homologous
Symbiodinium
types and exposed to combined heat and light stress. A suite of physiological indicators including chlorophyll
a
fluorescence, oxygen production and respiration, as well as pigment concentration consistently demonstrated lower metabolic costs and enhanced physiological tolerance of
Acropora tenuis
juveniles when hosting
Symbiodinium
type C1 compared with type D. In other studies, the same D-type has been shown to confer higher thermal tolerance than both C2 in adults and C1 in juveniles of the closely related species
Acropora millepora
. Our results challenge speculations that associations with type D are universally most robust to thermal stress. Although the heat tolerance of corals may be contingent on the
Symbiodinium
strain
in hospite
, our results highlight the complexity of interactions between symbiotic partners and a potential role for host factors in determining the physiological performance of reef corals.
Estimation of the number of founders of an invasive pest insect population: the fire antSolenopsis invictain the USA
Authors: Ross Kenneth G , Shoemaker D. DeWayne
Published: June 2008

Determination of the number of founders responsible for the establishment of invasive populations is important for developing biologically based management practices, predicting the invasive potential of species, and making inferences about ecological and evolutionary processes. The fire antSolenopsis invictais a major invasive pest insect first introduced into the USA from its native South American range in the mid-1930s. We use data from diverse genetic markers surveyed in the source population and the USA to estimate the number of founders of this introduced population. Data from different classes of nuclear markers (microsatellites, allozymes, sex-determination locus) and mitochondrial DNA are largely congruent in suggesting that 9–20 unrelated mated queens comprised the initial founder group to colonize the USA at Mobile, Alabama. Estimates of founder group size based on expanded samples from throughout the southern USA were marginally higher than this, consistent with the hypothesis of one or more secondary introductions of the ant into the USA. The rapid spread and massive population build-up of introducedS. invictaoccurred despite the loss of substantial genetic variation associated with the relatively small invasive propagule size, a pattern especially surprising in light of the substantial genetic load imposed by the loss of variation at the sex-determination locus.
Variable exposure and immunological response to Lyme diseaseBorreliaamong North Atlantic seabird species
Authors: Staszewski V , McCoy K.D , Boulinier T
Published: June 2008

Colonial seabirds often breed in large aggregations. These individuals can be exposed to parasitism by the tickIxodes uriae, but little is known about the circulation of pathogens carried by this ectoparasite, including Lyme diseaseBorrelia. Here we investigated the prevalence of antibodies (Ab) againstBorrelia burgdorferi sensu latoin seabird species sampled at eight locations across the North Atlantic. Using enzyme-linked immunosorbent assay tests, we found that the prevalence of anti-BorreliaAb in adult seabirds was 39.6% on average (over 444 individuals), but that it varied among colonies and species. Common guillemots showed higher seroprevalence (77.1%±5.9) than black-legged kittiwakes (18.6%±6.7) and Atlantic puffins (22.6%±6.3). Immunoblot-banding patterns of positive individuals, reflecting the variability ofBorreliaantigens against which Ab were produced, also differed among locations and species, and did not tightly match the prevalence ofBorreliaphylogroups previously identified in ticks collected from the same host individuals. These results represent the first report of the widespread prevalence of Ab againstBorreliawithin an assemblage of seabird species and demonstrate thatBorreliais an integrated aspect in the interaction between seabirds and ticks. More detailed studies on the dynamics ofBorreliawithin and among seabird species at different spatial scales will now be required to better understand the implications of this interaction for seabird ecology and the epidemiology of Lyme disease.
The genic view of plant speciation: recent progress and emerging questions
Authors: Lexer Christian , Widmer Alex
Published: June 2008

The genic view of the process of speciation is based on the notion that species isolation may be achieved by a modest number of genes. Although great strides have been made to characterize ‘speciation genes’ in some groups of animals, little is known about the nature of genic barriers to gene flow in plants. We review recent progress in the characterization of genic species barriers in plants with a focus on five ‘model’ genera:Mimulus(monkey flowers);Iris(irises);Helianthus(sunflowers);Silene(campions); andPopulus(poplars, aspens, cottonwoods). The study species in all five genera are diploid in terms of meiotic behaviour, and chromosomal rearrangements are assumed to play a minor role in species isolation, with the exception ofHelianthusfor which data on the relative roles of chromosomal and genic isolation factors are available. Our review identifies the following key topics as being of special interest for future research: the role of intraspecific variation in speciation; the detection of balancing versus directional selection in speciation genetic studies; the timing of fixation of alleles of major versus minor effects during plant speciation; the likelihood of adaptive trait introgression; and the identification and characterization of speciation genes and speciation gene networks.
Specificity in pollination and consequences for postmating reproductive isolation in deceptive Mediterranean orchids
Authors: Cozzolino Salvatore , Scopece Giovanni
Published: June 2008

The type of reproductive isolation prevalent in the initial stages of species divergence can affect the nature and rate of emergence of additional reproductive barriers that subsequently strengthen isolation between species. Different groups of Mediterranean deceptive orchids are characterized by different levels of pollinator specificity. Whereas food-deceptive orchid species show weak pollinator specificity, the sexually deceptiveOphrysspecies display a more specialized pollination strategy. Comparative analyses reveal that orchids with high pollinator specificity mostly rely on premating reproductive barriers and have very little postmating isolation. In this group, a shift to a novel pollinator achieved by modifying the odour bouquet may represent the main isolation mechanism involved in speciation. By contrast, orchids with weak premating isolation, such as generalized food-deceptive orchids, show strong evidence for intrinsic postmating reproductive barriers, particularly for late-acting postzygotic barriers such as hybrid sterility. In such species, chromosomal differences may have played a key role in species isolation, although strong postmating–prezygotic isolation has also evolved in these orchids. Molecular analyses of hybrid zones indicate that the types and strength of reproductive barriers in deceptive orchids with contrasting premating isolation mechanisms directly affect the rate and evolutionary consequences of hybridization and the nature of species differentiation.
TEAD mediates YAP-dependent gene induction and growth control
Authors: Zhao Bin , Ye Xin , Yu Jindan , Li Li , Li Weiquan , Li Siming , Yu Jianjun , Lin Jiandie D. , Wang Cun-Yu , Chinnaiyan Arul M. , Lai Zhi-Chun , Guan Kun-Liang
Published: June 2008

The YAP transcription coactivator has been implicated as an oncogene and is amplified in human cancers. Recent studies have established that YAP is phosphorylated and inhibited by the Hippo tumor suppressor pathway. Here we demonstrate that the TEAD family transcription factors are essential in mediating YAP-dependent gene expression. TEAD is also required for YAP-induced cell growth, oncogenic transformation, and epithelial–mesenchymal transition. CTGF is identified as a direct YAP target gene important for cell growth. Moreover, the functional relationship between YAP and TEAD is conserved in Drosophila Yki (the YAP homolog) and Scalloped (the TEAD homolog). Our study reveals TEAD as a new component in the Hippo pathway playing essential roles in mediating biological functions of YAP.
Female reproductive biology of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (Hymenoptera: Eulophidae), two parasitoids associated with the African Rice Gall Midge, Orseolia oryzivora (Diptera: Cecidomyiidae)
Authors: NACRO Souleymane , NÉNON Jean‐Pierre
Published: June 2008

We investigated the female reproductive system of Platygaster diplosisae (Hymenoptera: Platygastridae) and Aprostocetus procerae (= Tetrastichus pachydiplosisae) (Hymenoptera: Eulophidae), two parasitoids associated with the African rice gall midge, Orseolia oryzivora (Diptera: Cecidomyiidae). Both optical and electron microscopy were used. The female reproductive system of P. diplosisae includes two large ovaries of the meristic polytrophic‐type, each composed of several tens of ovarioles. The system includes also a venomous gland that extends to a common oviduct. This gland had a filiform secretory portion, in which the epithelium was thin and surrounded a common evacuation canal. The secretory cells secrete into a large reservoir. Parasitism due to P. diplosisae is gregarious. The female reproductive system of A. procerae includes two ovaries of the meristic polytrophic‐type, and each ovary has a few ovarioles. Each ovariole includes one or two oocytes, which can be seen in the vitellarium. Two accessory glands, which extend to the oviduct, are also visible. The secretory epithelium of the accessory gland is made up of a dense network of secretory cells surrounded by muscle fibers. Females of A. procerae pierce the tissues of the gall and probably deposit one egg on or close to the pupa of the midge. Aprostocetus procerae is a solitary parasitoid of the midge. The two parasitoids exploit the same host at different developmental stages. These findings improve our knowledge of the reproductive biology of these two parasitoids associated with the African rice gall midge, an important pest in Africa.
Life history and host specificity of the Japanese flea beetles Trachyaphthona sordida and T. nigrita (Coleoptera: Chrysomelidae), potential biological control agents against skunk vine, Paederia foetida (Rubiaceae), in the southeastern parts of the United States and Hawaii
Authors: OKAMOTO Chie , TSUDA Kiyoshi , YAMAGUCHI Daisuke , SATO Shinsuke , PEMBERTON Robert W. , YUKAWA Junichi
Published: June 2008

Skunk vine, Paederia foetida (Rubiaceae), is native to Asia and has been recognized as an invasive weedy vine of natural areas in Florida and Hawaii. Two insects, Trachyaphthona sordida and Trachyaphthona nigrita (Coleoptera: Chrysomelidae) from Japan are being considered as potential biological control agents against skunk vine. To gather fundamental information on their biology, we carried out field surveys and laboratory experiments in Kyushu, southern Japan, between 2003 and 2006. We found that T. sordida is commonly distributed in Kyushu and T. nigrita is restricted to the southern parts of Kagoshima Prefecture on the southern part of Kyushu. These species are fundamentally univoltine and adults appear in late April to early July. Trachyaphthona sordida overwinters as mature larvae and T. nigrita as mature larvae or rarely as adults. Larvae of both species feed on fine roots of P. foetida in the field and Serissa foetida (Rubiaceae) under rearing conditions, and they appear to have tribe‐level host specificity in their host range. On the basis of these results, we suggest that both species are suitable as biological control agents.
Systematic and morphological evaluations of a new species of Kuenburgia Schmitz (Diptera: Phoridae) with remarkable asymmetry of the male genitalia, including a bifurcated left surstylus
Authors: NAKAYAMA Hiroto
Published: June 2008

The monotypic genus Kuenburgia is revised, with description of a second species, K. bifurcata sp. nov., based on both sexes from Japan, and redescription of the type species, K. vidua, based on additional Japanese females. Kuenburgia bifurcata sp. nov. more closely fits the characters of Kuenburgia as represented by K. vidua than those of any other genera. The male genitalia of K. bifurcata sp. nov. lack the right surstylus, a character shared with the genus Trispiniphora, indicating a close relationship between these genera. The left surstylus of K. bifurcata sp. nov. is bifurcated and functions as a clasping device, balancing itself in a complex fashion with the right side of the epandrium and the left and right lobes of the hypandrium, and compensates for the loss of the right surstylus. The inner wall of the bifurcated left surstylus is well developed and also bifurcates along the left and right tines. It is considered to be homologous with the subepandrial sclerite + bacilliform sclerite in Eremoneura. The aedeagus of the male genitalia is composed of an inner core plate and an outer jacket plate, with the outer jacket plate wrapping in a sinistral fashion around the inner core plate.
Middle Jurassic fossils of the genus Sharasargus from Inner Mongolia, China (Diptera: Archisargidae)
Authors: ZHANG Kuiyan , YANG Ding , REN Dong
Published: June 2008

To date, only two species of the genus Sharasargus are known. These Upper Jurassic species were found in Mongolia and Kazakhstan, respectively. We herein describe two new species from the Middle Jurassic, which were found in Inner Mongolia, China. They are the oldest known fossils of this genus. A key to Sharasargus species is given.
Clonal reproduction by males of the ant Vollenhovia emeryi (Wheeler)
Authors: KOBAYASHI Kazuya , HASEGAWA Eisuke , OHKAWARA Kyohsuke
Published: June 2008

In colonies of the queen‐polymorphic ant Vollenhovia emeryi, some colonies produce only long‐winged (L) queens, while others produce only short‐winged (S) queens. At four nuclear microsatellite loci, males in the S colony had alleles that were different from those of their queen. This suggests that the nuclear genome of males is not inherited from their colony queen, as has also been described for Wasmannia auropunctata (Roger). In V. emeryi the possibility of male transfer from other colonies has not been ruled out because previous studies of this species have obtained only nuclear gene information. We analyzed both mitochondrial and nuclear genes for S queens, S males and L queens to clarify the origins of males. Sequence analyses showed that although S queens and S males shared the same mtDNA haplotype, they had a different genotype at a nuclear gene (long‐wavelength opsin) locus. Neighbor‐joining analysis based on the four microsatellite loci also suggested gene pool separation between S queens and S males. These results are consistent with predictions of clonal reproduction by males. While L queens share opsin genotypes with S males, they have very different mtDNA sequences. Hybridization in the near past between S queens and L males or gene transmission from S males to L queen populations in the present would explain these differences.
Molecular phylogeny and phylogeography of flightless beetles Parechthistatus gibber and Hayashiechthistatus inexpectus (Coleoptera: Cerambycidae) inferred from mitochondrial COI gene sequences
Authors: NAKAMINE Hiroshi , TAKEDA Makio
Published: June 2008

To elucidate the speciation patterns of two endemic flightless cerambycid beetles, Parechthistatus gibber and Hayashiechthistatus inexpectus, molecular phylogenetic analysis was carried out. A 1144 bp region of the cytochrome oxidase subunit I gene was sequenced for individuals from 51 local populations of these species. There were nine haplotype lineages of P. gibber, and H. inexpectus was included within a P. gibber lineage. These lineages were highly divergent and occurred in different regions. Based on previously published molecular change rates for the COI gene (1.5–2.3% per million years), the time of divergence of P. gibber COI haplotypes was inferred to be 3.0–4.6 million years ago, in the Pliocene.
Therapeutic target for chronic liver fibrosis by regulation of transforming growth factor‐beta
Authors: Jeong Kyu‐Shik
Published: June 2008

Liver fibrosis is the common scarring response of the liver to most chronic liver damage. Continuous chronic liver damage leads to a progressive accumulation of scarring proteins and finally, alters normal tissue structure and function by inducing fibrosis, cirrhosis and ultimately liver failure. Despite the considerable evolution on the study of liver fibrosis and cirrhosis during the past decade, a full understanding of liver fibrosis and cirrhosis still remains a goal for scientists. Although liver fibrosis and cirrhosis is mediated by various cytokines including tumor necrosis factor‐alpha, interleukin‐10 and transforming growth factor‐beta (TGF‐β), it has been shown that TGF‐β plays the most significant role in chronic liver disease. In early liver injury stage, TGF‐β is mainly released by necrotic hepatocytes, activated hepatic stellate cells and macrophages (Kupffer cells). In the middle stage of fibrosis or cirrhosis, TGF‐β is produced predominantly in hypoxic hepatocytes. Therefore, understanding the role of TGF‐β, and inhibiting TGF‐β release in chronic liver disease, might be the key to developing an effective therapeutic strategy for liver fibrosis, cirrhosis and chronic liver disease.
CDX2 protein expression in gallbladder carcinoma
Authors: Kang Gu Hyun , Lee Choong Sik , Park Eun Su , Kang Dae Young
Published: June 2008

Background and aim: CDX2 is a caudal‐type homeobox gene encoding a transcription factor that has an important role in proliferation and differentiation of the intestinal epithelium. Although CDX2‐mediated intestinal metaplasia and its association with gastric and esophageal carcinoma have been well described, its function in gallbladder carcinoma remains unclear. Methods: CDX2, MUC2 and MUC5AC expression were examined in carcinoma, intestinal metaplasia and dysplasia of the gallbladder by immunohistochemical staining. Results: CDX2 was not observed in the normal epithelium of the gallbladder but was expressed in 71.4% (20/28) of gallbladder carcinomas including 10 of 18 adenocarcinomas, not otherwise specified, 9 papillary adenocarcinomas and 1 intestinal‐type adenocarcinoma. In adenocarcinomas, CDX2 was observed more frequently in well differentiated types than in moderately and poorly differentiated types (P= 0.009). MUC2 and MUC5AC was expressed in 53.6% (15/28) and 71.4% (20/28) of gallbladder carcinomas, respectively. Both CDX2 and MUC2 were observed in 50.0% (14/28) and CDX2 expression was related to MUC2 (P= 0.006) rather than MUC5AC (P= 0.234) in gallbladder carcinomas. CDX2 was also expressed in intestinal metaplasia and dysplasia, which are considered to be premalignant conditions. Conclusions: These results suggest that CDX2 may play an important role in gallbladder carcinogenesis with intestinal differentiation.
Impact of fixatives on preservation of RNA in paraffin‐embedded and laser capture microdissected human tissues
Authors: Park In Suh , Kim Ye Ji , Kim Lucia , Choi Suk Jin , Han Jee Young , Chu Young Chae , Kim Han Kyum , Jin Xianji , Kim Joon Mee
Published: June 2008

Background and aim: Laser capture microdissection is used to obtain pure cell populations, thus allowing the study of molecular pathological mechanisms from specific cell populations, yet RNA from tissues fixed in formalin (the most common fixative for analysis of gene expression) is usually degraded during microdissection and RNA extraction. In this study we investigate the best fixative for use in the preparation of human tissues for laser capture microdissection, and for the preservation of RNA molecules and histomorphologic structure. Methods: Here we examine Methacarn, Carnoy's solution, 4% paraformaldehyde and 10% neutral‐buffered formalin. Forty‐three sides of various human organs were compared to determine the tissue‐fixing ability and RNA quality according to the fixatives. Results: Methacarn was the best suitable fixative for histomorphologic preservation as well as protection against RNA degradation after microdissection. However, Methacarn was not good for preservation of proteins. Conclusions: Methacarn is an excellent fixative for human tissue samples obtained by microdissection. It is an optimal fixative that is not only excellent for preservation of morphology, but also RNA extraction.
An Experimental Evaluation of an Atomization-Based Cutting Fluid Application System for Micromachining
Authors: Jun Martin B. G. , Joshi Suhas S. , DeVor Richard E. , Kapoor Shiv G.
Published: June 2008

An atomization-based cutting fluid application system is developed for micro-end milling. The system was designed to ensure spreading of the droplets on the workpiece surface based on the analysis of the atomized droplet impingement dynamics. The results of the initial experiments conducted to examine the viability of the system show that the cutting forces are lower and tool life is significantly improved with the atomized cutting fluids when compared to dry and flood cooling methods. Also, application of atomized cutting fluid is found to result in good chip evacuation and lower cutting temperature. Experiments were also conducted to study the effect of fluid properties on cutting performance, and the results show that cutting fluids with lower surface tension and higher viscosity perform better in terms of cutting forces.
Networked Fuzzy Control System for a High-Performance Drilling Process
Authors: Haber-Guerra Rodolfo E. , Haber-Haber Rodolfo , Andrés Diego Martín , Palomar Angel Alique
Published: June 2008

The high-performance drilling (HPD) process has a significant impact on production in many industries, such as the automotive, die/mold and aerospace industries. However, cutting conditions for drilling are generally chosen from a machining-data handbook, requiring operator experience and skill. In order to improve drilling efficiency while preserving tool life, the current study focuses on the design and implementation of a simple, optimal fuzzy-control system for drilling force. The main topic of this study is the design and implementation of a networked fuzzy controller. The control system consists of a two-input (force error and change of error), single-output (feed-rate increment) fuzzy controller with nine control rules, the sup-product compositional operator for the compositional rule of inference, and the center of area as the defuzzification method. The control algorithm is connected to the process through a multipoint interface (MPI) bus, a proprietary programming, and communication interface for peer-to-peer networking that resembles the PROFIBUS protocol. The output (i.e., feed-rate) signal is transmitted through the MPI; therefore, network-induced delay is unavoidable. The optimal tuning of the fuzzy controller using a maximum known delay is based on the integral time absolute error (ITAE) criterion. The goal is to obtain the optimal tuning parameters for the input scaling factors while minimizing the ITAE performance index. In this study, a step in the force reference signal is considered a disturbance, and the goal is to assess how well the system follows set-point changes using the ITAE criterion. The optimization is performed using the Nelder–Mead simplex (direct search) method. The main advantage of the approach presented herein is the design of a simple fuzzy controller using a known maximum allowable delay to deal with uncertainties and nonlinearities in the drilling process and delays in the network-based application. The results demonstrate that the proposed control strategy provides an excellent transient response without overshoot and a slightly higher drilling time than the CNC working alone (uncontrolled). A major issue in high performance drilling is the increase in cutting force and torque that occurs as the drill depth increases. Therefore, the fuzzy-control system reduces the influence of these factors, thus eliminating the risk of rapid drill wear and catastrophic drill breakage.
An Adaptive Fuzzy Controller for Constant Cutting Force in End-Milling Processes
Authors: Xu Chengying , Shin Yung C.
Published: June 2008

A novel multilevel fuzzy control system is introduced and implemented for online force control of end-milling processes to increase machining productivity and improve workpiece quality, where the cutting force is maintained at its maximum allowable level in the presence of different variations inherent in milling processes, such as tool wear, workpiece geometry, and material properties. In the controller design, the fuzzy rules are generated heuristically without any mathematical model of the milling processes. An adaptation mechanism is embedded to tune the control parameters online, and the resultant closed-loop system is guaranteed to be stable based on the input-output passivity analysis. In the experiment, the control algorithm is implemented using a National Instrument real-time control computer in an open architecture control environment, where high metal removal rates are achieved and the cycle time is reduced by up to 34% over the case without any force controller and by 22% compared with the regular fuzzy logic controller, thereby indicating its effectiveness in improving productivity for actual machining processes.
Modeling of Material Removal Rate in Micro-ECG Process
Authors: Gaikwad Kishore S. , Joshi Suhas S.
Published: June 2008

Microelectrochemical grinding (micro-ECG) is a variant of electrochemical grinding (ECG) process, in which material is removed by a combination of electrolytic dissolution and abrasive action that take place in a small interelectrode gap. This paper discusses analytical modeling of the material removal phenomenon in micro-ECG process to predict material removal rate. In the model, the phenomena, which contribute to the material removal in the process by electrolytic and abrasive actions, have been considered; these include streaming potential in the electrochemical action and shearing forces due to the flow of electrolyte through interelectrode gap and the abrasive action of grinding wheel. Two configurations of the process, viz., surface and cylindrical micro-ECG, have been modeled. The results have been validated by CFD simulation in the case of surface micro-ECG process, and specific experimentation in the case of cylindrical micro-ECG process.
Directionally Independent Failure Prediction of End-Milling Tools by Tracking Increasing Chaotic Noise at the Machining Frequencies Due to Wear
Authors: Suprock Christopher A. , Roth John T.
Published: June 2008

Accurate on-line forecasting of a tool’s condition during end-milling operations is advantageous to the functionality and reliability of automated industrial processes. The ability to disengage the tool prior to catastrophic failure reduces manufacturing costs, excessive machine deterioration, and personnel hazards. Rapid computational feedback describing the system’s state is critical for realizing a practical failure forecasting model. To this end, spectral analysis by fast Fourier type algorithms allows a rapid computational response. The research described herein explores the development of nontraditional real fast Fourier transform (discrete cosine transform) based algorithms performed in unique higher-dimensional states of observed data sets. Moreover, the developed Fourier algorithm quantifies chaotic noise rather than relying on the more traditional observation of system energy. By increasing the vector dimensionality of the discrete cosine transform, the respective linear transform basis more effectively cross correlates the transform data into fewer (more significant) transform coefficients. Thus, a single vector in orthogonally higher-dimensional space is observed instead of multiple orthogonal vectors in single-dimensional space. More specifically, a novel modal reduction technique is utilized to track trends measured from triaxial force dynamometer signals. This transformation effectively achieves both modal reduction and directional independence by observing the chaotic noise instead of system energy. Algorithm output trends from six end-milling life tests are tracked from both linear and pocketing maneuvers in order to demonstrate the technique’s capabilities. In all six tests, the algorithm predicts impending tool failure with sufficient time for tool removal.
Variation Source Identification in Manufacturing Processes Based on Relational Measurements of Key Product Characteristics
Authors: Loose Jean-Philippe , Zhou Shiyu , Ceglarek Dariusz
Published: June 2008

Variation source identification for manufacturing processes is critical for product dimensional quality improvement, and various techniques have been developed in recent years. Most existing variation source identification techniques are based on a linear fault-quality model, in which the relationships between process faults and product dimensional quality measurements are linear. In practice, many dimensional measurements are actually nonlinearly related to the process faults: For example, relational dimension measurements such as the relative distance between features are used to monitor composite tolerances. This paper presents a variation source identification methodology in the presence of these relational dimension measurements. In the proposed methodology, the joint probability density of the measurements is determined as a function of the process parameters; then, series of statistical comparisons are performed to differentiate and identify the variation source. A case study is also presented to illustrate the effectiveness of the methodology.
Novel Laser/Water-Jet Hybrid Manufacturing Process for Cutting Ceramics
Authors: Molian Raathai , Neumann Clayton , Shrotriya Pranav , Molian Pal
Published: June 2008

Laser and water-jet manufacturing processes are independently used to cut monolithic and composite ceramics. While these processes offer many advantages over diamond sawing and other abrasive processes, the energy efficiency, precision, cutting speed, and environmental threats remain as barriers to their continued success. This is partly attributed to the material removal mechanisms, which are melting, and subsequent evaporation (laser) and energy-intensive erosive wear (water jet). In this paper, we describe a novel laser and water-jet (LWJ) hybrid manufacturing process that enables the synergistic effects of CO2 laser and pressurized pure water jet, facilitating precise material removal by thermal shock-induced fracture and overcoming the deficiencies listed above. Experiments of the LWJ effects on the cutting of aluminum nitride, an electronic ceramic substrate, are presented. The most exciting results are very narrow kerf dictated by the crack width; the absence of thermally affected zone, slag formation, chemical decomposition; and controlled thermal cracking, implying that the LWJ process is far superior to conventional laser cutting of ceramics. The LWJ process also improved the surface finish while reducing energy losses in the process. The practical realization of the LWJ manufacturing process could be a potential alternative to diamond saw, high-power laser, and high-pressure abrasive water-jet methods for machining hard and brittle ceramics.
Calibration of Palletized Workpiece Systems for Microfactories
Authors: Honegger Andrew , Kapoor Shiv G. , DeVor Richard E.
Published: June 2008

Kinematic couplings have been used to create palletized system for part transfer in a microfactory. While kinematic couplings provide high repeatability, calibration is needed to achieve high interchangeability accuracy. In this paper, a generalized artifact-based methodology for pallet calibration and workpiece registration is developed. This calibration method uses the microfactory machines to both machine and measure artifacts to estimate the interchangeability errors. The error sources affecting the accuracy of calibration are analyzed and techniques are suggested to reduce these errors. Finally, the methodology is applied and validated for a specific microfactory application.
A Mechanistic Model of Cutting Forces in Micro-End-Milling With Cutting-Condition-Independent Cutting Force Coefficients
Authors: Lee Han Ul , Cho Dong-Woo , Ehmann Kornel F.
Published: June 2008

Complex three-dimensional miniature components are needed in a wide range of industrial applications from aerospace to biomedicine. Such products can be effectively produced by micro-end-milling processes that are capable of accurately producing high aspect ratio features and parts. This paper presents a mechanistic cutting force model for the precise prediction of the cutting forces in micro-end-milling under various cutting conditions. In order to account for the actual physical phenomena at the edge of the tool, the components of the cutting force vector are determined based on the newly introduced concept of the partial effective rake angle. The proposed model also uses instantaneous cutting force coefficients that are independent of the end-milling cutting conditions. These cutting force coefficients, determined from measured cutting forces, reflect the influence of the majority of cutting mechanisms involved in micro-end-milling including the minimum chip-thickness effect. The comparison of the predicted and measured cutting forces has shown that the proposed method provides very accurate results.
Fabrication of High Aspect Ratio Porous Microfeatures Using Hot Compaction Technique
Authors: Chen Peng , Kim Gap-Yong , Ni Jun
Published: June 2008

High aspect ratio porous microfeatures are becoming more important in the modern industry. However, the fabrication of such features under a mass production environment remains a challenge when robustness, cost effectiveness, and high productivity requirements are required. In this study, the forming of such porous microfeatures using hot compaction was investigated. A hot compaction experimental setup was designed and fabricated that is capable of performing high temperature operation (700°C), quick heatup, and avoiding oxidation. 3D thermal simulation of the experimental setup was conducted to investigate the heat transfer performance and internal temperature distribution, which was then used as a reference for the experiment. Hot compaction experiments were carried out, and the effects of compression force and temperature on the quality in terms of powder consolidation strength and porosity were investigated. In addition, the achievable aspect ratio and taper angle were also discussed.
A Submicron Multiaxis Positioning Stage for Micro- and Nanoscale Manufacturing Processes
Authors: Balasubramanian Ashwin , Jun Martin B. G. , DeVor Richard E. , Kapoor Shiv G.
Published: June 2008

A piezoelectrically driven, submicron XY-positioning stage with multiprocess capability is developed and then integrated into two micro∕nanoscale manufacturing processes to improve their performance. The design is based on the HexFlex™ mechanism but is modified to improve structural robustness using a combination of factorial design, linear programming, and finite element analysis. Performance analysis reveals travel ranges of 16μm (X-axis) and 8μm (Y-axis), positioning accuracies of 87nm (X-axis) and 92nm (Y-axis), and overall stiffnesses of 32N∕μm (X-axis) and 36N∕μm (Y-axis). A comparison of microfluidic channels manufactured with a micromachine tool (mMT) alone and with the stage stacked on the mMT shows an improvement in feature accuracy from 870nmto170nm. The stage is integrated with an electrochemical deposition setup. Nanowire structures with sharp angles are fabricated. The diameter of these nanowires shows an improvement in uniformity by decreasing the standard deviation of diameter variation from 2.088μmto0.009μm.
Design, Fabrication, and Characterization of Metal Embedded Microphotonic Sensors
Authors: Zhang Xugang , Jiang Hongrui , Li Xiaochun
Published: June 2008

Recent developments in integrated microphotonics have led to unprecedented potential toward robust sensor enhancements for manufacturing systems. These micron-sized subwavelength structured photonic sensors could allow critical thermomechanical phenomena in manufacturing processes to be monitored while offering immunity to electromagnetic interference, resistance to hostile environments, multiplexing capabilities, and high rates of data collection. To implement these novel sensors into real manufacturing processes, the microphotonic sensors can be embedded at critical locations in metallic structures, which are heavily used in hostile manufacturing environments. This paper presents the study of design, fabrication, and characterization of integrated microring sensors. Various thin film optical materials were studied and single ring resonators were designed. A new approach to fabricate metal embedded microring sensors was developed. Metal embedded optical microring temperature sensors were characterized. The Q factor of the metal embedded microring sensors was measured to be around 2000, while the free spectral range was about 5.2nm. The temperature sensitivity of the metal embedded microring sensor was 24.2pm∕°C.
Gap Adjustable Molten Metal DoD Inkjet System With Cone-Shaped Piston Head
Authors: Lee Taik-Min , Kang Tae Goo , Yang Jeong Soon , Jo Jeongdai , Kim Kwang-Young , Choi Byung-Oh , Kim Dong-Soo
Published: June 2008

In this paper, we present the design, fabrication, and performance test of a gap adjustable molten metal drop-on-demand (DoD) inkjet system with a cone-shaped piston head, which can eject a droplet of lead-free molten solder at high temperature. The gap adjustable mechanism with the cone-shaped piston head is proposed for optimizing the gap distance between the chamber wall and piston head. The droplet diameter and velocity can be controlled in a wide range by moving the initial gap distance and minutely by controlling the chamber pressure. Stability and satellite can be partly adjusted by controlling the initial gap distance and the chamber pressure, respectively. The working temperature is improved by locating the piezoelectric actuator at the outside of the furnace and by inserting the insulation block between the print head and the actuator. From a practical point of view, the molten metal DoD inkjet system presents a simple structure for easily interchangeable nozzle parts, even though the nozzle is choked. The gap adjustable molten metal DoD inkjet system with cone-shaped piston head has great potential as a manufacturing tool for direct printing a viscous material at various temperatures. It is expected to be applicable in many industrial fields including semiconductor packaging, electrode bonding, printed electronics, information, and display industry.
Microstructure-Level Machining Simulation of Carbon Nanotube Reinforced Polymer Composites—Part II: Model Interpretation and Application
Authors: Dikshit A. , Samuel J. , DeVor R. E. , Kapoor S. G.
Published: June 2008

The microstructure-level finite element machining model developed in Part I of this paper is used to perform a detailed analysis of the failure mechanisms that occur while machining the carbon nanotube (CNT) reinforced polycarbonate composites. The chip formation in plain polycarbonate (PC) is seen to be influenced by the ductile failure mode. For the composite containing 1.75% by weight of CNTs (Composite A), the polymer fails in the ductile mode. The presence of CNTs is seen to result in CNTs protruding from the machined surface and subsurface damage. The low thermal conductivity of the polymer phase is seen to result in the formation of adiabatic shear bands in plain PC and Composite A. As the CNT loading is increased to 5% by weight, the failure in the polymer phase is seen to be predominantly brittle in nature. The presence of the larger percentage of CNTs is also seen to offset the formation of adiabatic shear bands. The machining model has also been used to successfully predict the machining behavior of CNT composites with tailored microstructures. Simulation experiments with varying CNT alignment, aspect ratio, percentage loading, and cutting velocity were conducted to study the effects of these factors on cutting forces. The results show that the machining model in combination with the material model is an effective tool to design CNT composites with emphasis both on the mechanical properties and machinability.
Intelligent Tool-Path Segmentation for Improved Stability and Reduced Machining Time in Micromilling
Authors: Mayor J. Rhett , Sodemann Angela A.
Published: June 2008

This paper presents the method of variable-feedrate intelligent segmentation as an enhanced approach to feedrate optimization in micromilling that overcomes detrimental scale effects in the process and leads to improved stability and decreased machining time. Due to the high tool-size to feature-size ratio present in micromilling, the maximum allowable feedrate is limited by the sampling rate of the real-time trajectory generation and motion control system. The variable-feedrate intelligent segmentation method is proposed to compensate for the feedrate limitation by intelligent selection of the interpolation technique applied to segments along the tool path in order to reduce the trajectory generation computation time and enable increased sampling frequency. The increased sampling frequency allows higher maximum feedrates providing for increased productivity and improved process stability. The performance of the novel intelligent segmentation approach was benchmarked against recent non-rational B-splines (NURBS) feedrate optimization techniques. Results from the numerical evaluation of the intelligent segmentation technique have demonstrated significant reductions in machining time, with a maximum reduction of over 50% recorded. Furthermore, the results from the study demonstrate the advantages of the intelligent segmentation method in enhancing process stability and maintaining, or marginally decreasing, process error. The variable feedrate intelligent segmentation method developed in this study provides, therefore, an enhanced methodology for path planning in high-speed, high-precision micromilling operations.