bluuebunny/crossref_metadata_2025 huggingface dataset:
The BTB-ZF gene Bm-mamo regulates pigmentation in silkworm caterpillars
Authors: Wu Songyuan , Tong Xiaoling , Peng Chenxing , Luo Jiangwen , Zhang Chenghao , Lu Kunpeng , Li Chunlin , Ding Xin , Duan Xiaohui , Lu Yaru , Hu Hai , Tan Duan , Dai Fangyin
Published: January 2024

The color pattern of insects is one of the most dazzling adaptive evolutionary phenotypes. However, the molecular regulation of this color pattern is not fully understood. In this study, we found that the transcription factor Bm-mamo is responsible for
black dilute
(
bd
) allele mutations in the silkworm. Bm-mamo belongs to the BTB zinc finger family and is orthologous to mamo in
Drosophila melanogaster
. This gene has a conserved function in gamete production in
Drosophila
and silkworms and evolved a pleiotropic function in the regulation of color patterns in caterpillars. We found that
Bm-mamo
can comprehensively regulate the expression of related pigment synthesis and cuticular protein genes to form color patterns. This indicates that insects have a genetic basis for coordinate regulation of the structure and shape of the cuticle, as well as color patterns. This genetic basis provides the possibility for constructing the complex appearances of some insects. This study provides new insight into the regulation of color patterns.The color patterns of insects are highly exquisite and significantly divergent. The metabolism of pigments is the material basis for insect coloration. However, the cuticle of insects plays an important role as a scaffold for carrying pigment particles. Cuticular proteins are some of the main components of the cuticle. This study showed that a BTB-ZF family transcription factor protein, Bm-mamo, can comprehensively regulate melanin synthesis and the expression of multiple cuticular protein genes. Hence, insects have a genetic basis for integrated control of cuticle and color pattern construction, which enables them to produce complex appearances.
Mobile barrier mechanisms for Na+-coupled symport in an MFS sugar transporter
Authors: Hariharan Parameswaran , Shi Yuqi , Katsube Satoshi , Willibal Katleen , Burrows Nathan D. , Mitchell Patrick , Bakhtiiari Amirhossein , Stanfield Samantha , Pardon Els , Kaback H. Ronald , Liang Ruibin , Steyaert Jan , Viner Rosa , Guan Lan
Published: January 2024

While many 3D structures of cation-coupled transporters have been determined, the mechanistic details governing the obligatory coupling and functional regulations still remain elusive. The bacterial melibiose transporter (MelB) is a prototype of the Na
+
-coupled major facilitator superfamily transporters. With a conformational nanobody (Nb), we determined a low-sugar affinity inward-facing Na
+
-bound cryoEM structure. Collectively with the available outward-facing sugar-bound structures, both the outer and inner barriers were localized. The N-and C-terminal residues of the inner barrier contribute to the sugar selectivity pocket. When the inner barrier is broken as shown in the inward-open conformation, the sugar selectivity pocket is also broken. The binding assays by isothermal titration calorimetry revealed that this inward-facing conformation trapped by the conformation-selective Nb exhibited a greatly decreased sugar-binding affinity, suggesting the mechanisms for the substrate intracellular release and accumulation. While the inner/outer barrier shift directly regulates the sugar-binding affinity, it has little or no effect on the cation binding, which is also supported by molecular dynamics simulations. Furthermore, the use of this Nb in combination with the hydron/deuterium exchange mass spectrometry allowed us to identify dynamic regions; some regions are involved in the functionally important inner barrier-specific salt-bridge network, which indicates their critical roles in the barrier switching mechanisms for transport. These complementary results provided structural and dynamic insights into the mobile barrier mechanism for cation-coupled symport.
Apical annuli are specialised sites of post-invasion secretion of dense granules in Toxoplasma
Authors: Chelaghma Sara , Ke Huiling , Barylyuk Konstantin , Krueger Thomas , Koreny Ludek , Waller Ross F
Published: January 2024

Apicomplexans are ubiquitous intracellular parasites of animals. These parasites use a programmed sequence of secretory events to find, invade, and then re-engineer their host cells to enable parasite growth and proliferation. The secretory organelles micronemes and rhoptries mediate the first steps of invasion. Both secrete their contents through the apical complex which provides an apical opening in the parasite’s elaborate inner membrane complex (IMC) – an extensive subpellicular system of flattened membrane cisternae and proteinaceous meshwork that otherwise limits access of the cytoplasm to the plasma membrane for material exchange with the cell exterior. After invasion, a second secretion programme drives host cell remodelling and occurs from dense granules. The site(s) of dense granule exocytosis, however, has been unknown. In Toxoplasma gondii, small subapical annular structures that are embedded in the IMC have been observed, but the role or significance of these apical annuli to plasma membrane function has also been unknown. Here, we determined that integral membrane proteins of the plasma membrane occur specifically at these apical annular sites, that these proteins include SNARE proteins, and that the apical annuli are sites of vesicle fusion and exocytosis. Specifically, we show that dense granules require these structures for the secretion of their cargo proteins. When secretion is perturbed at the apical annuli, parasite growth is strongly impaired. The apical annuli, therefore, represent a second type of IMC-embedded structure to the apical complex that is specialised for protein secretion, and reveal that in Toxoplasma there is a physical separation of the processes of pre- and post-invasion secretion that mediate host-parasite interactions.
Dipper throated optimization with deep convolutional neural network-based crop classification for remote sensing image analysis
Authors: Alotaibi Youseef , Rajendran Brindha , Rani K. Geetha , Rajendran Surendran
Published: January 2024

Problem

With the rapid advancement of remote sensing technology is that the need for efficient and accurate crop classification methods has become increasingly important. This is due to the ever-growing demand for food security and environmental monitoring. Traditional crop classification methods have limitations in terms of accuracy and scalability, especially when dealing with large datasets of high-resolution remote sensing images. This study aims to develop a novel crop classification technique, named Dipper Throated Optimization with Deep Convolutional Neural Networks based Crop Classification (DTODCNN-CC) for analyzing remote sensing images. The objective is to achieve high classification accuracy for various food crops.

Methods

The proposed DTODCNN-CC approach consists of the following key components. Deep convolutional neural network (DCNN) a GoogleNet architecture is employed to extract robust feature vectors from the remote sensing images. The Dipper throated optimization (DTO) optimizer is used for hyper parameter tuning of the GoogleNet model to achieve optimal feature extraction performance. Extreme Learning Machine (ELM): This machine learning algorithm is utilized for the classification of different food crops based on the extracted features. The modified sine cosine algorithm (MSCA) optimization technique is used to fine-tune the parameters of ELM for improved classification accuracy.

Results

Extensive experimental analyses are conducted to evaluate the performance of the proposed DTODCNN-CC approach. The results demonstrate that DTODCNN-CC can achieve significantly higher crop classification accuracy compared to other state-of-the-art deep learning methods.

Conclusion

The proposed DTODCNN-CC technique provides a promising solution for efficient and accurate crop classification using remote sensing images. This approach has the potential to be a valuable tool for various applications in agriculture, food security, and environmental monitoring.
Numerical and biomass growth study of Bulimulus bonariensis (Rafinesque, 1833) (Gastropoda: Bulimulidae) under laboratory conditions
Authors: Díaz Ana Carolina , Martin Stella Maris
Published: January 2024

Bulimulus bonariensis is considered a species of relevance to agribusiness, having been declared a pest with indirect damage because of its negative effects on several crops such as soybeans, chickpeas, and corn in central and northern Argentina. The objective of this work was to analyze the growth pattern of a population born under laboratory conditions, to explore population aspects such as survival and mortality, to estimate the age and size at gonadal maturity and first reproduction, and to contribute to the knowledge of the reproductive biology of this gastropod. From the clutches obtained, the basic biologic parameters were calculated and the individuals hatched under laboratory conditions counted and measured every two weeks. The clutches contained an average of 44 eggs, which took about 13.7 days to hatch at a birth rate of 41.82%. The growth pattern in the five clutches was analyzed individually, and the logistic model used was the one with the highest degree of fit to that observed growth pattern, followed by the Gompertz model, and finally the von Bertalanffy model. In addition, the models were applied to the 102 specimens analyzed together as a cohort, where the best fitting model was also proved to be the logistic growth model. A concave type III survival curve was obtained from the horizontal life table. The cohort was reduced by 48% during the first 50 days after birth. Beyond one month of hatching, life expectancy gradually increased and remained high between 65–302 days of life. After day 330, life expectancy decreased and only 13.72% exceeded one year of birth, with an average length of 16.68 mm. The last specimen died after 23 months at a total length of 20.24 mm, and the life expectancy was estimated at almost three years. In addition, it was inferred that gonadal maturity, when these gastropods reach 12 mm of total shell length, is reached after 200 days of life. Therefore, the individuals that are born are able to reproduce for the first time a year after birth, when they have the approximate size of 16.68 mm.
Ruptured Pulmonary Hydatid Cyst with Multiple Small Bronchopleural Fistula Formations: A Case Report
Authors: Sahu Asish Anand Subrata , Vare Ajay , Kaginalkar Varsha Rote
Published: January 2024

Hydatid disease is a zoonosis caused by Echinococcus granulosus. It manifests as cystic lesions, most commonly found in the liver and lungs, and rarely in other parts of the body. The disease occurs when a human host accidentally ingests contaminated food containing eggs from canine waste products. Since the clinical characteristics of this disease are nonspecific, radiological investigations play a crucial role in diagnosis. Diagnostic challenges arise due to atypical imaging features of complicated hydatid cysts. A 40-year-old female patient presented with fever, breathlessness, chest pain, and an unproductive cough persisting for eight days. Upon examination, she was in hypovolaemic shock, and an intercostal drainage tube had been inserted in the left sixth intercostal space. The chest radiograph revealed a dense, homogeneous opacity in the left hemithorax, partially compressing the left lung medially. An High-resolution Computed Tomography (HRCT) thorax showed a thick-walled cavity with an air-fluid level and layered membranes in the dependent part of the cavity, indicating a water lily sign in the left lower lobe of the lung, suggesting a ruptured hydatid cyst. The patient underwent cystectomy with suturing of a small bronchopleural fistula. Computed Tomography (CT) is the preferred imaging modality, especially for assessing associated complications and ruling out differentials in cases of ruptured pulmonary hydatid cysts.
Prevalence of Dental Anomalies in Maxillary Lateral Incisors: An Institutional Cross-sectional Study from Karnataka
Authors: Varalakshmi C , Rairam Surabhi , Ratnakar P , Patil Veerendra , Kanimil-li Samanvitha , Neema KV
Published: January 2024

ntroduction: The majority of dental abnormalities are found in third molars, followed by permanent maxillary lateral incisors. The occurrence of these dental anomalies varies among different ethnic groups; hence, it is of prime importance for clinicians to know and understand the incidence of dental anomalies among the local population. Aim: To analyse the prevalence of dental anomalies in relation to permanent maxillary lateral incisors in the Karnataka region. Materials and Methods: A cross-sectional study was conducted in the Department of Conservative Dentistry and Endodontics of HKES’s S Nijalingappa Institute of Dental Science and Research, Kalaburgi, Karnataka, India from July 2022 to December 2022. A total of 1,116 subjects, aged between 15 and 50 years, were randomly screened. Each subject was clinically examined, and radiographs were taken for patients with dental anomalies. The five dental anomalies studied were congenitally missing permanent maxillary lateral incisors, peg laterals, dens in dente, talon’s cusp, and palato-gingival groove. Statistical analysis was performed using SPSS version 26. Descriptive statistics were estimated in terms of frequency and percentage. Results: A total of 43 subjects were found to have anomalies associated with the maxillary lateral incisor, including pegshaped laterals (1.25%-14), dens in dente (0.81%-09), congenitally missing (0.45%-05), talon’s cusp (0.27%-03), and palato-gingival groove (1.07%-12). Conclusion: Anomalies in permanent maxillary lateral incisors were noted in 3.85% of the Karnataka population.
Respiratory Syncytial Virus-related Lower Respiratory Tract Infections in Neonatal and Post-neonatal Babies: A Series of Four Cases
Authors: Kamble Niranjan , Bhaskar Monisha , Gadgeesh Prajwal B , Rangaswamy Darshan Rajatadri
Published: January 2024

Respiratory Syncytial Virus (RSV) is a highly contagious seasonal virus that is the leading cause of acute Lower Respiratory Tract Infections (LRTI) in the paediatric age group and is one of the leading causes of death in children under five in developing countries. There is evidence that severe RSV infection and hospitalisation in early life increase the risk of recurrent wheezing, childhood asthma, and allergic sensitisation. Even though RSV being a major global health concern, very few papers concentrate on the neonatal period in India. The present case series presents four cases (three females and one male baby) highlighting the impact of RSV in neonatal and post-neonatal infants in India. The cases highlight the diversity of presentation; one infant required prolonged High-flow Nasal Cannula (HFNC) support, while two needed just symptomatic care. The importance of Polymerase Chain Reaction (PCR) in resource-constrained situations is highlighted as diagnostic issues are examined. Treatment focuses on supportive care; oxygen and respiratory support are provided in more severe cases. The present study emphasises the need for early detection and preventative measures, such as using novel treatments like nirsevimab. The present case series advocates for focused therapies and additional research in the Indian paediatric environment, adding insightful perspectives to the expanding body of knowledge on RSV.
Learning Crisis at Elementary School Level in India: Need for Systemic Interventions
Authors: Garg Mamta
Published: January 2024

Right to Education is considered to be empowering each and every child of the nation by bringing educational opportunity to their doorsteps. Developing countries have made tremendous progress in getting children into schools. But learning is not guaranteed. Evidences suggests that children who are in school are not learning the basics of literacy and numeracy or the additional knowledge and skills necessary for their all-round development as specified in the policies. An estimated 617 million children and adolescents around the world are unable to reach minimum proficiency levels in reading and mathematics. Without foundational learning, students often fail to thrive later in school or when they join the workforce. World Bank also indicated that we are in the midst of a global learning crisis that threatens countries’ efforts to build human capital – the skills and know-how needed for the jobs of the future. This learning crisis is the greatest global challenge to preparing children and adolescents for life, work and active citizenship. In India also, where GER at elementary level is 100%, more than fifty percent of children are ‘learning poor’. This paper is an attempt to highlight the dynamics of the learning crisis in India in terms of its antecedents and repercussions. Further, evidence based systemic interventions have been proposed to eliminate the present and future crises, and ensure that every child learns.
A 5 Year Bibliometric Review of Programming Language Research Dynamics in Southeast Asia (2018-2023)
Authors: Delmo Arawela Lou , Despi John Robertson , Arpon Peter Kyle Jr
Published: January 2024

Aims: To conduct a systematic examination and bibliometric analysis of Scopus-indexed literature focusing on emerging trends in programming languages research within Southeast Asia.

Study Design: This study employs a mixed method approach, incorporating both qualitative and bibliometric analysis.

Place and Duration of Study: Publication data for review was obtained from the Scopus database, covering the period from 2018 to 2023, with a specific focus on the progress in programming language and semantics research within ASEAN countries.

Methodology: We used the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) protocol to collect publication data. Bibliometric data was visualized through Biblioshiny and VOSviewer.

Results: From 2018 to 2023, the research production involving programming languages and semantics across ASEAN countries has been strong, yielding a total of 233 documents from 160 unique sources. However, the annual growth rate was at -10.87%. There was a total of 882 authors with only 10 sole authors in the field. 46.78% of the documents had international co-authorship with an average of 4.03 authors per document. The literature spanned across 764 unique author keywords and 7424 citations with an average of 11.12 citations per document.

Conclusion: Southeast Asia has a rich and collaborative research space in the field of Programming Languages but it faces several barriers such as the absence of a unified research agenda, the lack of adequate funding, and the relatively weak industrial base.
Impact of Khat Chewing on Serum Uric Acid and Albuminuria Levels in Yemeni Type II Diabetes Mellitus Patients
Authors: Sa'ad Arafat M A , Obaidi Abdulkaraim Al , AL-Eryani Ekram , Al-Khawlani Abdulkarim , AL-Hamoodi Khater Gh. H. , Yang Qingzhen , Kayd Mohammed Musead A. , Altaher Tibyan Abd Almajed , Mahjaf Ghanem Mohammed , Abedalmula Waha Ismail Yahia , Gorish Babbiker Mohammed Taher
Published: January 2024

Background: Diabetes mellitus is the major cause of end-stage renal disease and is a common endocrine illness defined by chronic hyperglycemia. In addition to diabetes, substance addiction is considered to be a cause of renal issues. The World Health Organization has classed khat (Catha edulis) as an illicit substance. Khat interferes with regular physiological activities, which may have negative health impacts on organs and systems. 

Objectives: To determine the effect of khat and uric acid on nephropathy in type II diabetes mellitus.

Materials and Methods: This is an analytical, cross-sectional study that was conducted on 215 males aged 35 to 55 years who had previously been diagnosed with type II diabetes mellitus and were visiting AL- Thawra General Hospital in Ibb City. The diabetic person was corresponded in age and BMI by the control participant. The subjects were divided into two groups. There were 105 people with type II diabetes mellitus (59% chewing Khat and 46% not chewing Khat), 110 people were healthy and did not have type II diabetes (44% of them chewed Khat and 66% did not chew Khat). 

Results: A significant increase in albuminuria and proteinuria within the normal range in the diabetes mellitus Khat Chewer group compared to the diabetes mellitus Non-Khat Chewer group (p˂0.001). However, no significant differences were seen in the healthy control group.

Conclusion: Khat chewing has a strong effect on those with type II diabetes and increases the progression of kidney nephropathy. There was an association between khat chewing and higher uric acid levels in both diabetic and non-diabetic patients.
Evaluation of Nano-DAP on Plant Growth, Enzymatic Activity and Yield in Paddy (Oryza sativa L.)
Authors: Maloth Anusha , Thatikunta Ramesh , Parida Binaya Kumar , Naik D. Saida , Varma N. Rama Gopala
Published: January 2024

A field experiment was conducted during Rabi 2022-23 at the College of Agriculture, Rajendranagar, Hyderabad, Telangana, focusing on the impact of using nano-DAP through foliar application on plant growth, yield, enzymatic activity and nutrient content in paddy variety KNM 1638. The experiment employed a randomized block design (RBD) with seven different treatments, each replicated three times. The study recorded various growth parameters, enzymatic activity, yield and nutrient content. The results demonstrated that, application of 100% NK + 75% P in combination with two foliar sprays of nano-DAP at both tillering and panicle initiation stages (T6) led to superior plant growth parameters such as number of tillers hill-1 (13.18), total dry matter (42.12 g hill-1), increased yield parameters such as number of productive tillers hill-1 (11.25), number of grains panicle-1 (297) and yield (7530.86 kg ha-1) and nutrient content such as N (2.33%), P (0.19%) and K content (1.68%). The enzyme Glutamine Synthetase (GS) activity was found to be significantly higher with the application of 100% NPK with two foliar sprays of nano-DAP at tillering and panicle initiation stages (T3). While the acid and alkaline phosphatase activity recorded maximum with 100%.
Evaluation of First-Line Coagulation Tests in Highly Active Antiretroviral Therapy (HAART) Naïve and Treated Group of HIV Infected Subjects
Authors: Martina Ngwu Amauche , Lawrence Ozoemena Chiadikobi , Elijah Umeh Okechukwu , Basil Ugwu Ifeanyichukwu , Innocent Ozoume Chibuike
Published: January 2024

Background: Coagulation disorders are common in patients with Human Immunodeficiency virus (HIV). Coagulation abnormalities occur as a result of HIV-related thrombocytopenia, induced hepatotoxicity due to highly active antiretroviral therapy (HAART) that impairs liver function and diminishes the function and synthesis of coagulation factors. The aim of this study was to evaluate prothrombin time (PT), activated partial thromboplastin time (APTT), platelet count, mean platelet volume, plateletcrit and platelet distribution width in HAART-naïve HIV infected patients, HAART treated and HIV-seronegative controls.

Place and Duration of Study: Department of Haematology and antiretroviraltherapies (ART) clinic both of Enugu State University of Science and Technology Teaching Hospital, between March and June 2023.

Methodology: A total of 150 study participants, consisting of 50 HAART-naïve HIV-infected subjects, 50 HIV-infected subjects who were taking HAART, and 50 HIV-seronegative apparently healthy subjects, were included. Coagulation tests such as PT, APTT were determined by manual procedures. Platelet counts (PC), mean platelet volume (MPV), plateletcrit (PCT), platelet distribution width (PDW) were analyzed by Mindray/BC-5150 automated analyzer. The data were analyzed using SPSS version 21. Analysis of variance (ANOVA) and Pearson correlation analysis were used. P-Value < 0.05 was considered as statistically significant.

Results: Mild thrombocytopenia (100-<150 x 109/L) was found in 48% of HIV-infected subjects who were taking HAART, 76% mild thrombocytopenia and 24% moderate thrombocytopenia (50-<100 x109/L) was found in HAART-naïve HIV-infected subjects, but no thrombocytopenia was found in apparently healthy HIV-seronegative control. Prothrombin time and APTT were significantly higher, whereas PC and PDW was significantly lower in HIV-infected subjects (both who were taking HAART and HAART-naïve) than HIV-seronegative subjects (p<0.05). Prothrombin time and APTT were significantly higher, and PC was significantly lower in HAART-naïve HIV-infected subjects than HIV-infected subjects who were taking HAART. In Pearson correlation analysis, PT and APTT has shown a significant negative correlation with a PC in those taking HAART and HAART-naïve HIV-infected subjects, whereas significant positive correlation was found in HIV-seronegative subjects.

Conclusion: Prothrombin time and APTT significantly increased, whereas platelet count and PDW significantly decreased in HIV-infected subjects who were taking HAART and HAART-naïve. Basic coagulation parameters need to be monitored regularly in HIV-infected subjects in Enugu.
Generating Blue and Red Luminescence from ZnO/Poly(ethylene glycol) Nanocomposites Prepared Using an In‐Situ Method
Authors: Abdullah M. , Morimoto T. , Okuyama K.
Published: October 2003

The peak of the luminescence spectrum of zinc oxide (ZnO) is usually observed above 500 nm (yellow region). By in‐situ growth of ZnO nanoparticles in a poly(ethylene glycol) (PEG) matrix, we have succeeded in producing ZnO/polymer composites with stable luminescence peaks down to 465 nm (blue region). The unbalanced precursor molarity approach, where the molarity of one precursor (LiOH) is several times larger than the molarity represented by a chemical reaction balance, was used. The blue luminescence, which was accompanied by an enhancement of luminescence intensity, was observed at very high LiOH concentrations. This was probably due to the simultaneous reduction in the crystalline size and improvement in the crystallinity. Doping ZnO nanoparticles with europium also generated a red luminescence at 616 nm, due to the 5D0 →7F2 transition of Eu ions.
Frequency Upconversion of 800 nm Ultrashort Pulses by Two‐Photon Absorption in a Stilbenoid Compound‐Doped Polymer Optical Fiber
Authors: Jordan G. , Kobayashi T. , Blau W.J. , Pfeiffer S. , Hörhold H.‐H.
Published: October 2003

We present the results of a study of frequency upconversion of femtosecond optical pulses in a step‐index polymer optical fiber that uses a stilbenoid compound as an active dopant. Intense blue emission is observed in the doped poly(methyl methacrylate) (PMMA) fiber when it is longitudinally pumped at 800 nm by 175 fs optical pulses. By means of the intensity‐dependent transmission method, the two‐photon absorption cross‐section is deduced. Our study illustrates that the combination of a well‐designed organic chromophore incorporated into a fiber geometry is appealing for the development of an upconversion blue polymer laser.
Holographic Recording in a Photoactive Elastomer
Authors: Zhao Y. , Bai S. , Asatryan K. , Galstian T.
Published: October 2003

This work explores the use of photoactive elastomers as elastic holographic materials. Holographic gratings were recorded on stretched films of an azobenzene elastomer, which is composed of a side‐chain liquid‐crystalline polymer with azobenzene mesogens, grafted to the rubbery polybutadiene block of a styrene–butadiene–styrene (SBS) triblock copolymer. The grating‐formation dynamics measurements revealed the formation of two gratings of different natures resulting from the coupled mechanical and optical effects. A first grating, formed quickly upon exposure, is due to the photoisomerization of oriented azobenzene groups. A second grating, developed at longer exposure times, may originate from changes in the anisotropic structure of the SBS matrix, which is induced by the photochemical phase transition of azobenzene mesogens. The first grating is unstable, but the second grating remains in relaxed films. Both mechanisms can be enhanced by deformation of the film.
Synthesis of Novel Photochromic Films by Oxidation Polymerization of Diarylethenes Containing Phenol Groups
Authors: Uchida K. , Takata A. , Saito M. , Murakami A. , Nakamura S. , Irie M.
Published: October 2003

We report the synthesis of some diarylethene derivatives attached to phenol moieties, which show remarkable photochromic reactions. A dithienylethene group attached to the o‐phenol moiety (1,2‐bis[2,4‐dimethyl‐5‐(o‐hydroxyphenyl)‐3‐thienyl]hexafluorocyclopentene) was polymerized according to Hay's method; the resulting film was insoluble to any solvents, and showed no absorption band attributable OH group in its IR spectrum. Isomeric dithienylethenes attached to m‐ and p‐phenol moieties did not form films under the same oxidation conditions, but instead formed films by copolymerization with 4,4′‐dihydroxyphenyl ether. Although the homopolymer film and copolymer films showed reversible photochromic reactions by alternate irradiation with UV and visible light, the coloration was not remarkable. Polymerization of closed‐ring isomers of the dithienylethenes did not give pre‐polymers and instead decomposed, while the closed‐ring isomer of a bisbenzothienylethene derivative attached to the o‐phenol moiety (1,2‐bis[2‐methyl‐6‐(o‐hydroxyphenyl)‐1‐benzothiophen‐3‐yl]hexafluorocyclopentene) formed a polymer film by the same procedure. This polymer film showed a remarkable photochromic reaction, indicating the photo‐reactive conformation was fixed in polymer matrix, and X‐ray diffraction measurements show that the film is in the amorphous phase. The photochromic reaction can also be monitored by IR spectroscopy, making it applicable for non‐destructive read‐out recording films.
Silica Nanocasting of Simple Cellulose Derivatives: Towards Chiral Pore Systems with Long‐Range Order and Chiral Optical Coatings
Authors: Thomas A. , Antonietti M.
Published: October 2003

Aqueous solutions of hydroxypropyl cellulose with cholesteric superstructures were employed as templates in a silica nanocasting process, and the resulting pore structures were characterized by polarization microscopy, circular dichroism, X‐ray scattering, transmission electron microscopy, and sorption measurements. Whereas the local pore architecture corresponds to a cast of single cellulose strands and their statistical aggregates, the averaged structure on larger scales keeps the cholesteric character, with the cholesteric pitch just slightly shortened.
Thermally Induced Transient Absorption of Light by Poly(3,4‐ethylenedioxythiophene):Poly(styrene sulfonic acid) (PEDOT:PSS) Films: A Way to Probe Charge‐Carrier Thermalization Processes
Authors: Meskers S.C.J. , van Duren J.K.J. , Janssen R.A.J.
Published: October 2003

Infrared‐induced transient absorptions in the millisecond and sub‐picosecond time domains have been used to study the dynamics of charge carriers of a conducting polymer, poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS). On the millisecond timescale, the transient absorption is ascribed to a thermal effect induced by absorbed infrared light. The decay of the transient absorption is limited by the transport of heat from the polymer film to the substrate and corresponds to the decay kinetics of infrared‐induced changes in the resistivity of the material. Near 1.5 eV, the infrared‐induced absorption can be modeled in terms of an interband transition. The assignment of the optical transients in terms of carrier heating opens the possibility to study charge carrier thermalization processes using short laser pulses. Pump‐probe spectroscopy on a sub‐picosecond timescale shows that the initial thermalization of the excited charge carriers occurs with a time constant of less than 500 fs, i.e., faster than for noble metals.
Inorganic Macroporous Films from Preformed Nanoparticles and Membrane Templates: Synthesis and Investigation of Photocatalytic and Photoelectrochemical Properties
Authors: Shchukin D.G. , Caruso R.A.
Published: October 2003

Colloidal dispersions of titania, zirconia, tin oxide, indium oxide, and ceria have been successfully used to impregnate membrane templates and form the respective metal oxide (MO) porous films. The use of alumina and iron oxide sols in the same procedure, however, resulted in compact structures. By mixing different nanoparticle solutions before impregnation, final inorganic films containing two metal oxides, of variable metal oxide ratios, were obtained. The porous inorganic materials were analyzed in terms of surface area, pore size, film thickness, and crystallinity. The mechanism of nanoparticle infiltration and particle adsorption to the template walls is proposed based on the stability of the inorganic film and a study of the influence of either the sol concentration or washing times on the amount of inorganic substance incorporated in the hybrid material. The photocatalytic decomposition of an organic pollutant, 2‐chlorophenol, was demonstrated for the porous titania material along with the structures containing mixtures of titania with zirconia, indium oxide, and tin oxide. A ratio of 9:1 TiO2/MO gave the highest photocatalytic activity, which was higher than the activity of Degussa P25 for the TiO2/In2O3 and TiO2/SnO2 systems under the same conditions. The titania films have also been attached to substrates—glass or indium tin oxide (ITO) surfaces—and the photoelectrochemical properties of the porous film attained. A comparison with a spin‐coated titania film (prepared from the same colloidal dispersion) showed that the structured porous inorganic film has two times the photoelectrochemical efficiency as the spin‐coated film.
Comparative Carrier Transport Characteristics in Organic Field‐Effect Transistors with Vapor‐Deposited Thin Films and Epitaxially Grown Crystals of Biphenyl‐Capped Thiophene Oligomers
Authors: Yanagi H. , Araki Y. , Ohara T. , Hotta S. , Ichikawa M. , Taniguchi Y.
Published: October 2003

Carrier transport characteristics in organic field‐effect transistors were compared for vapor‐deposited thin films and epitaxially grown needle crystals of biphenyl‐capped thiophene oligomers with different lengths of the thiophene units. The hole mobility of the thin films deposited on Si/SiO2 substrate was improved up to 0.17 cm2 V–1 s–1 by formation of platelet crystallites with a domain size of a few micrometer. The hole transport in the epitaxial needle crystals grown on the KCl surface depended upon the molecular orientation with respect to the channel direction. The orientation of the needle axis bridging over the source–drain electrodes increased the mobility since π‐electronic interaction through the parallel stack of the linear molecules enhanced the carrier transport along the needle. The deposition condition and electronic energy levels of the oligomers, depending on the length of the thiophene units, also affected their characteristics.
Photochemically Controlled Photonic Crystals
Authors: Kamenjicki M. , Lednev I.K. , Mikhonin A. , Kesavamoorthy R. , Asher S.A.
Published: October 2003

We have developed photochemically controlled photonic crystals that may be useful in novel recordable and erasable memories and/or display devices. These materials can operate in the UV, visible, or near‐IR spectral regions. Information is recorded and erased by exciting the photonic crystal with ∼ 360 nm UV light or ∼ 480 nm visible light. The information recorded is read out by measuring the photonic crystal diffraction wavelength. The active element of the device is an azobenzene‐functionalized hydrogel, which contains an embedded crystalline colloidal array. UV excitation formscis‐azobenzene while visible excitation formstrans‐azobenzene. The more favorable free energy of mixing ofcis‐azobenzene causes the hydrogel to swell and to red‐shift the photonic crystal diffraction. We also observe fast nanosecond, microsecond, and millisecond transient dynamics associated with fast heating lattice constant changes, refractive index changes, and thermal relaxations.
Bismuth–Ceramic Nanocomposites with Unusual Thermal Stability via High‐Energy Ball Milling
Authors: Meitl M.A. , Dellinger T.M. , Braun P.V.
Published: October 2003

Electrically conducting nanocomposites of bismuth metal and insulating ceramic phases of SiO2 and MgO were generated via high‐energy ball milling for 24 h using zirconia milling media. The resulting nanocomposites contain Bi nanoparticles with sizes down to 5 nm in diameter. The morphology is a strong function of the oxide phase: specifically, the Bi appears to wet MgO while it forms spherical nanoparticles on the SiO2. X‐ray diffraction measurements indicate a nominal bismuth grain size of 50 nm, and peak fitting to a simple bidisperse model yields a mixture of approximately 57 % bulk bismuth and 43 % 27 nm diameter crystallites. Nanoparticles as small as 5 nm are observed in transmission electron microscopy (TEM), but may not constitute a significant volume fraction of the sample. Differential scanning calorimetry reveals dramatic broadening in the temperatures over which melting and freezing occur and a surprising persistence of nanostructure after thermal cycling above the melting point of the Bi phase.
Characterization and Field‐Emission Properties of Needle‐like Zinc Oxide Nanowires Grown Vertically on Conductive Zinc Oxide Films
Authors: Tseng Y.‐K. , Huang C.‐J. , Cheng H.‐M. , Lin I.‐N. , Liu K.‐S. , Chen I.‐C.
Published: October 2003

Needle‐like ZnO nanowires with high density are grown uniformly and vertically over an entire Ga‐doped conductive ZnO film at 550 °C. The nanowires are grown preferentially in the c‐axis direction. The X‐ray diffraction (XRD) θ‐scan curve shows a full width at half maximum (FWHM) value of 2°. This indicates that the c‐axes of the nanorods are along the normal direction of the substrate surface. The investigation using high‐resolution transmission electron microscopy (HRTEM) confirmed that each nanowire is a single crystal. A room‐temperature photoluminescence (PL) spectrum of the wires consists of a strong and sharp UV emission band at 380 nm and a weak and broad green–yellow band. It reveals a low concentration of oxygen vacancies in the ZnO nanowires and their high optical quality. Field electron emission from the wires was also investigated. The turn‐on field for the ZnO nanowires was found to be about 18 V μm–1 at a current density of 0.01 μA cm–2. The emission current density from the ZnO nanowires reached 0.1 mA cm–2 at a bias field of 24 V μm–1.
Self‐Assembly of Polyaniline—From Nanotubes to Hollow Microspheres
Authors: Zhang L. , Wan M.
Published: October 2003

By simply changing the molar ratio of the dopant to monomer, the morphology of salicylic acid (SA)‐doped polyaniline (PANI) can be changed from one‐dimensional nanotubes (∼ 109–150 nm in diameter) to three‐dimensional hollow microspheres (∼ 1.5–3.1 μm in diameter) via a self‐assembly process. Freeze–fracture electron microscopy (FFEM) proved that hollow spherical micelles composed of SA/aniline act as templates in the formation of either nanotubes or hollow spheres. FTIR and X‐ray diffraction measurements suggest that the hydrogen bond of the –OH group of SA with the amine group of PANI might be a driving force for self‐assembling hollow microspheres, while the hydrogen bond through hydrogen and oxygen of the adjacent SA doped on the polymer chains results in short‐range order of the counter‐ions along the polymer chain in the nanotubes.
Block Copolymers as a Tool for Nanomaterial Fabrication
Authors: Lazzari M. , López‐Quintela M.A.
Published: October 2003

In this review the latest developments regarding the use of self‐assembled copolymers for the fabrication of nanomaterials will be presented and their real potential evaluated. Most of the strategies reported so far are herewith classified under two main approaches: a) use of block copolymers as nanostructured materials, either “as they are” or through a selective isolation of one or more component blocks, and b) as templates for the synthesis of metallic or semiconducting nanomaterials. The problems of the orientation and large‐scale order of self‐organizing block copolymer mesophases will be also introduced, due to their importance as a route towards further improvements of the nanofabrication means.
Novel Ferroelectric Polymer Composites with High Dielectric Constants
Authors: Dang Z.‐M. , Lin Y.‐H. , Nan C.‐W.
Published: October 2003

A very simple blending and hot‐molding technique has been used to prepare novel ferroelectric polymer composites of poly(vinylidene fluoride) (PVDF) and Ni (see Figure) with a high dielectric constant of weak frequency‐ and temperature‐dependence. The polymer composites are flexible and of low dielectric loss. The electrical behavior observed in such composites can be described well using percolation theory.
Self‐Assembled Electroluminescent Polymers Derived from Terpyridine‐Based Moieties
Authors: Yu S.‐C. , Kwok C.‐C. , Chan W.‐K. , Che C.‐M.
Published: October 2003

A family of self‐assembled zinc terpyridyl polymers that exhibit emission colors ranging from violet to yellow (see Figure) with high photoluminescence (PL) quantum yields has been developed. These polymers are promising light‐emitting materials for electroluminescent (EL) devices, and the EL of the Zn terpyridyl polymer in the blue region is particularly desirable.
Tailoring Discotic Mesophases: Columnar Order Enforced with Hydrogen Bonds
Authors: Gearba R.I. , Lehmann M. , Levin J. , Ivanov D.A. , Koch M.H.J. , Barberá J. , Debije M.G. , Piris J. , Geerts Y.H.
Published: October 2003

Hydrogen bonding can be used to significantly enforce the intra‐columnar stacking order in discotic mesogens. The ordered hexagonal columnar mesophase of a HAT‐CONHR derivative is characterized by the smallest inter‐disk distance ever found in columnar liquid crystals (3.18–3.20 Å). This additional attractive interaction between the disks in the column results in a regular disc stacking and thus in a high charge‐carrier mobility over the whole investigated temperature range (from room temperature up to 200 °C).
Surface‐Enhanced Raman Scattering of Small Molecules from Silver‐Coated Silicon Nanopores
Authors: Chan S. , Kwon S. , Koo T.‐W. , Lee L.P. , Berlin A.A.
Published: October 2003

New ways of detecting low concentrations of analytes, which could be used as part of integrated on‐chip devices, are offered by surface‐enhanced Raman‐scattering substrates fabricated on the nanoscale. The ability of metal surfaces to amplify a Raman‐scattering signal (see Figure) is combined with an enlarged substrate surface area, allowing orders of magnitude enhancement for the detection of rhodamine 6G and adenine.
30 nm Channel Length Pentacene Transistors
Authors: Zhang Y. , Petta J.R. , Ambily S. , Shen Y. , Ralph D.C. , Malliaras G.G.
Published: October 2003

Advances in sample fabrication have allowed the fabrication of pentacene transistors with channel lengths down to 30 nm. The Figure shows a transistor with a channel length and width of 27 nm and 130 nm, respectively. Graceful scaling of the current–voltage characteristics as a function of channel length and width is demonstrated.
Nanoporous Structures Prepared by an Electrochemical Deposition Process
Authors: Shin H.‐C. , Dong J. , Liu M.
Published: October 2003

Free‐standing metal foam structures with nano‐dendritic walls of copper and tin are fabricated by an electrochemical deposition process. This unique structure is attributed to the concurrent generation of hydrogen bubbles with extremely fast metal deposition at high cathodic current densities. The Figure shows a typical example of the foam‐like structure of tin deposits with walls composed of nano‐dendritic branches.
Synthesis of Ordered Mesoporous Carbon with Bimodal Pore System and High Pore Volume
Authors: Lu A.‐H. , Schmidt W. , Spliethoff B. , Schüth F.
Published: October 2003

Ordered mesoporous carbon, named as NCC‐1, has been synthesized via a nanocasting process using SBA‐15 as the template and diluted furfuryl alcohol solution as the carbon source. NCC‐1 shows a bimodal pore size distribution (see Figure) in the mesopore range and a high pore volume up to 3.2 cm3 g–1. Since the pore systems are independently generated at different stages during the synthesis, they can also be modified independently.
Highly Efficient and Thermally Stable Electro‐optic Polymer from a Smartly Controlled Crosslinking Process
Authors: Luo J. , Haller M. , Li H. , Kim T.‐D. , Jen A.K.‐Y.
Published: October 2003

A nonlinear optical polymer, which is thermoreversibly crosslinkable (see Figure), has been developed to overcome the nonlinearity–stability trade‐off in poled polymers. High poling efficiency has been achieved after controlled, mild lattice hardening via the Diels–Alder crosslinking reaction. The resulting material exhibits a large electro‐optic coefficient (r33 = 76 pm V–1 at 1.3 μm) and excellent temporal stability.
Ultralong, Well‐Aligned Single‐Walled Carbon Nanotube Architectureson Surfaces
Authors: Huang S. , Maynor B. , Cai X. , Liu J.
Published: October 2003

A novel fast‐heating chemical vapor deposition (CVD) method to grow ultralong, well‐aligned single‐walled carbon nanotubes (SWNTs) is developed. The control of lengths and growth directions provided by this CVD technique is used to fabricate ordered, large‐scale nanotube structures. The Figure shows an ultralong SWNT.
Efficient Field Emission from Highly Aligned, Graphitic Nanotubes Embedded with Gold Nanoparticles
Authors: Kim K. , Lee S.H. , Yi W. , Kim J. , Choi J.W. , Park Y. , Jin J.‐I.
Published: October 2003

By utilizing highly aligned graphitic nanotubes embedded with gold nanoparticles an efficient field‐emission device can be constructed. These have been synthesized by first preparing composite nanotubes consisting of poly(p‐phenylenevinylene) and Au nanoparticles by chemical vapor deposition polymerization, followed by carbonization. The Figure shows transmission electron microscopy images of these nanotubes.
Templated Self‐Assembly of Block Copolymers: Effect of Substrate Topography
Authors: Cheng J.Y. , Ross C.A. , Thomas E.L. , Smith H.I. , Vancso G.J.
Published: October 2003

Topographical confinement is used to template the formation of nanoscale domains in a self‐assembled block copolymer film. The topographical template controls the row spacings and feature dimensions of the copolymer and can deliberately introduce defects in the arrays (see Figure). For example, a sharp edge feature leads to a missing domain and pins the lateral position of the polymer array. (See also inside cover.)
High Coercive Field for Nanoparticles of CoFe2O4in Amorphous Silica Sol–Gel
Authors: Hutlova A. , Niznansky D. , Rehspringer J.‐L. , Estournès C. , Kurmoo M.
Published: October 2003

Unusually high magnetic hardness, characterized by a coercive field of 2 T at 2 K, has been observed for 12 nm particles of CoFe2O4(15%) in amorphous silica prepared by the sol–gel technique and sintered at 1000 °C. Field‐ and temperature‐dependence magnetization data (see Figure) for these particles and those of 3.2 nm suggest that dipolar interaction between particles is responsible for this enhancement.
Reversible Switching Between Optically Isotropic and Birefringent States in a Bent‐Core Liquid Crystal
Authors: Jákli A. , Huang Y.‐M. , Fodor‐Csorba K. , Vajda A. , Galli G. , Diele S. , Pelzl G.
Published: October 2003

The tilted smectic liquid‐crystal phase of an ester‐based bent‐core mesogen (see Figure) is optically isotropic due to the combination of suitable tilt and opening angles of the bent cores. In electric fields, V‐shaped switching between isotropic and birefringent states is observed. Both the antiferroelectric and ferroelectric states consist of optically active domains due to the twisted molecular structure.