An analysis of E-governance in Pakistan from the lens of the Chinese governance model

In this era of digitalization, the role of information and communication technology (ICT) has significantly increased. The integration of ICT into the government system has improved efficiency and working processes. Some countries such as China have successfully integrated ICT into their governance system. However, many other countries especially the developing world are yet to effectively utilize the role of ICT in their governance structure and these countries are struggling to produce a better governance system. It is, therefore, imperative for the developing world to learn from successful nations and devise their governance systems so that ICT can be fully utilized and produce good governance. However, such comparative analyses are not done as such to bring strengths and weaknesses in the integration of ICT into the governance system especially in developing countries' governance systems. This study contributes by conducting a comparative study on the China-Pakistan e-government progress. China has widely implemented e-government, which has helped the country to ensure good governance. Pakistan, on the other hand, is also moving towards digitalization and making efforts to implement e-government. This research examines the United Nations' E-Government Development Index (EGDI) reports and rankings. The findings of our research show that China has significantly improved its ranking, whereas Pakistan's ranking has indicated a gradual decline except for the year 2008. This happened because of a lack of investment in infrastructure, scarcity of financial resources, weak institutional capabilities, and limited access to advanced technologies. Moreover, there is a big gap between public policy and public implementation in Pakistani scenarios. However, it has been dug out in this study that employing the Chinese model and seeking cooperation with China can improve e-governance ranking and overall governance in Pakistan. The study advances the understanding of e-governance and its challenges in Pakistan and the findings of the study will assist researchers, policymakers, and officials in the implementation and development of e-projects in Pakistan.

Interface Manipulations Using Cross-Linked Underlayers and Surface-Active Diblock Copolymers to Extend Morphological Diversity in High-χ Diblock Copolymer Thin Films

Top and bottom interfaces of high-χ cylinder-forming polystyrene-block-maltoheptaose (PS-b-MH) diblock copolymer (BCP) thin films are manipulated using cross-linked copolymer underlayers and a fluorinated phase-preferential surface-active polymer (SAP) additive to direct the self-assembly (both morphology and orientation) of BCP microdomains into sub-10 nm patterns. A series of four photo-cross-linkable statistical copolymers with various contents of styrene, a 4-vinylbenzyl azide cross-linker, and a carbohydrate-based acrylamide are processed into 15 nm-thick cross-linked passivation layers on silicon substrates. A partially fluorinated analogue of the PS-b-MH phase-preferential SAP additive is designed to tune the surface energy of the top interface. The self-assembly of PS-b-MH thin films on top of different cross-linked underlayers and including 0-20 wt % of SAP additive is investigated by atomic force microscopy and synchrotron grazing incidence small-angle X-ray scattering analysis. The precise manipulation of the interfaces of ca. 30 nm thick PS-b-MH films not only allows the control of the in-plane/out-of-plane orientation of hexagonally packed (HEX) cylinders but also promotes epitaxial order-order transitions from HEX cylinders to either face-centered orthorhombic or body-centered cubic spheres without modifying the volume fraction of both blocks. This general approach paves the way for the controlled self-assembly of other high-χ BCP systems.

Prolonged Repellent Activity of Plant Essential Oils against Dengue Vector, Aedes aegypti

Repellents are effective personal protective means against outdoor biting mosquitoes. Repellent formulations composed of EOs are finding increased popularity among consumers. In this study, after an initial screening of 11 essential oils (EOs) at the concentration of 33 μg/cm², five of the most repellent EOs, Perovskia atriplicifolia, Citrus reticulata (fruit peels), C. reticulata (leaves), Mentha longifolia, and Dysphania ambrosioides were further investigated for repellent activity against Aedes aegypti mosquitoes in time span bioassays. When tested at the concentrations of 33 μg/cm², 165 μg/cm² and 330 μg/cm², the EO of P. atriplicifolia showed the longest repellent effect up to 75, 90 and 135 min, respectively, which was followed by C. reticulata (peels) for 60, 90 and 120 min, M. longifolia for 45, 60 and 90 min, and C. reticulata (leaves) for 30, 45 and 75 min. Notably, the EO of P. atriplicifolia tested at the dose of 330 μg/cm² showed complete protection for 60 min which was similar to the commercial mosquito repellent DEET. Gas chromatographic-mass spectrometric analyses of the EOs revealed camphor (19.7%), limonene (92.7%), sabinene (24.9%), carvone (82.6%), and trans-ascaridole (38.8%) as the major constituents of P. atriplicifolia, C. reticulata (peels), C. reticulata (leaves), M. longifolia, and D. ambrosioides, respectively. The results of the present study could help develop plant-based commercial repellents to protect humans from dengue mosquitoes.

Harnessing of Spatially Confined Perovskite Nanocrystals Using Polysaccharide-based Block Copolymer Systems

Metal halide perovskite nanocrystals (PVSK NCs) are generally unstable upon their transfer from colloidal dispersions to thin film devices. This has been a major obstacle limiting their widespread application. In this study, we proposed a new approach to maintain their exceptional optoelectronic properties during this transfer by dispersing brightly emitting cesium lead halide PVSK NCs in polysaccharide-based maltoheptaose-block-polyisoprene-block-maltoheptaose (MH-b-PI-b-MH) triblock copolymer (BCP) matrices. Instantaneous crystallization of ion precursors with favorable coordination to the sugar (maltoheptaose) domains produced ordered NCs with varied nanostructures of controlled domain size (≈10-20 nm). Confining highly ordered and low dimension PVSK NCs in polysaccharide-based BCPs constituted a powerful tool to control the self-assembly of BCPs and PVSK NCs into predictable structures. Consequently, the hybrid thin films exhibited excellent durability to humidity and stretchability with a relatively high PL intensity and photoluminescence quantum yield (>70%). Furthermore, stretchable phototransistor memory devices were produced and maintained with a good memory ratio of 10⁵ and exhibited a long-term memory retention over 10⁴ s at a high strain of 100%.

Organic β-cyclodextrin Nanoparticle: An Efficient Building Block Between Functionalized Poly(pyrrole) Electrodes and Enzymes

Glyconanoparticles (GNPs) made by self-assembly of carbohydrate-based polystyrene-block-β-cyclodextrin copolymer are used as a building block for the design of nanostructured biomaterials of electrode. The firm immobilization of GNPs is carried out on electrochemically generated polymer, poly(pyrrole-adamantane), and copolymer, poly(pyrrole-adamantane)/poly(pyrrole-lactobionamide) via host-guest interactions between adamantane and β-cyclodextrin. The ability of GNPs for the specific anchoring of biological macromolecules is investigated using glucose oxidase enzyme modified by adamantane groups as a protein model (GOx-Ad). The immobilization of GOx-Ad is carried out by incubation of an aqueous enzyme solution on a coating of GNPs adsorbed on a platinum electrode. The presence of immobilized GOx-Ad is evaluated in aqueous glucose solution by potentiostating the underlying platinum electrode at 0.7 V/SCE for the electro-oxidation of H₂ O₂ generated by the enzyme. The analytical performance of the bioelectrodes for the detection of glucose is compared to control electrodes prepared without GNPs or without electropolymerized films. The better permeability of copolymer compared to polymer and the possibility to elaborate two alternating layers of GNPs and GOx-Ad are clearly observed. The best amperometric response is recorded with a multilayered bioelectrode displaying a wide linear range linear range of the calibration curve: 68 µmol L^-1 to 0.1 mol L^-1 .

Sequential Infiltration Synthesis into Maltoheptaose and Poly(styrene): Implications for Sub-10 nm Pattern Transfer

Vapor phase infiltration into a self-assembled block copolymer (BCP) to create a hybrid material in one of the constituent blocks can enhance the etch selectivity for pattern transfer. Multiple pulse infiltration into carbohydrate-based high-χ BCP has previously been shown to enable sub-10 nm feature pattern transfer. By optimizing the amount of infiltrated material, the etch selectivity should be further improved. Here, an investigation of semi-static sequential infiltration synthesis of trimethyl aluminum (TMA) and water into maltoheptaose (MH) films, and into hydroxyl-terminated poly(styrene) (PS-OH) films, was performed, by varying the process parameters temperature, precursor pulse duration, and precursor exposure length. It was found that, by decreasing the exposure time from 100 to 20 s, the volumetric percentage on included pure Al₂O₃ in MH could be increased from 2 to 40 vol% at the expense of a decreased infiltration depth. Furthermore, the degree of infiltration was minimally affected by temperature between 64 and 100 °C. Shorter precursor pulse durations of 10 ms TMA and 5 ms water, as well as longer precursor pulses of 75 ms TMA and 45 ms water, were both shown to promote a higher degree, 40 vol%, of infiltrated alumina in MH. As proof of concept, 12 nm pitch pattern transfer into silicon was demonstrated using the method and can be concluded to be one of few studies showing pattern transfer at such small pitch. These results are expected to be of use for further understanding of the mechanisms involved in sequential infiltration synthesis of TMA/water into MH, and for further optimization of carbohydrate-based etch masks for sub-10 nm pattern transfer. Enabling techniques for high aspect ratio pattern transfer at the single nanometer scale could be of high interest, e.g., in the high-end transistor industry.

Prevalence of Xerostomia and Associated Systemic Risk Factors in Riyadh, Saudi Arabia: A Cross-sectional Study

Purpose: Xerostomia is a feeling of dry mouth and may result in poor oral hygiene, dental caries, mucosal lesions and burning mouth syndrome. Medication, systemic diseases and stress are common etiological factors of xerostomia. The present study investigated the prevalence of xerostomia and explored the possible risk factors associa­ted with this condition among Saudi population. Methods: The present cross-sectional study was conducted on 418 participants visiting at Maxillofacial clinic, at secondary care hospital, Riyadh.  Demographic data and complete medical history were obtained from participants. All participants were requested to fill the Xerostomia-Inventory (XI) questionnaire. Comparisons between mean scores of XI-inventory and categorical variables like gender, comorbid conditions were made with students t-test or Wilcoxon test. Chi-square or Fischer’s Exact test were used for comparison between categorical variables like gender and responses to XI-items (No/Yes). P value of <0.05 was considered significant. All analysis was done on JMP-version-12. Results: Total 418-participants with mean age (41.1 ± 12.8 years) were included in the study in which 302-participants (72.2%) were female and 116-participants (27.8%) were male. Xerostomia’s prevalence was 24.7% and it was higher in males (34%) as compared to females (21%). A statistically-significant association was found between xerostomia and participant’s age (P < 0.0001). The participants with systemic illness showed a significantly higher mean Xerostomia Inventory (XI) score as compared to the healthy patients. In our study population common comorbid conditions were hypertension and diabetes. Conclusion: The prevalence of xerostomia increases with increasing age and it has strong positive co-relation with chronic systemic diseases.

Poly(styrene)-block-Maltoheptaose Films for Sub-10 nm Pattern Transfer: Implications for Transistor Fabrication

Sequential infiltration synthesis (SIS) into poly(styrene)-block-maltoheptaose (PS-b-MH) block copolymer using vapors of trimethyl aluminum and water was used to prepare nanostructured surface layers. Prior to the infiltration, the PS-b-MH had been self-assembled into 12 nm pattern periodicity. Scanning electron microscopy indicated that horizontal alumina-like cylinders of 4.9 nm diameter were formed after eight infiltration cycles, while vertical cylinders were 1.3 nm larger. Using homopolymer hydroxyl-terminated poly(styrene) (PS-OH) and MH films, specular neutron reflectometry revealed a preferential reaction of precursors in the MH compared to PS-OH. The infiltration depth into the maltoheptaose homopolymer film was found to be 2.0 nm after the first couple of cycles. It reached 2.5 nm after eight infiltration cycles, and the alumina incorporation within this infiltrated layer corresponded to 23 vol % Al2O3. The alumina-like material, resulting from PS-b-MH infiltration, was used as an etch mask to transfer the sub-10 nm pattern into the underlying silicon substrate, to an aspect ratio of approximately 2:1. These results demonstrate the potential of exploiting SIS into carbohydrate-based polymers for nanofabrication and high pattern density applications, such as transistor devices.

CRISPR/Cas9: A powerful genome editing technique for the treatment of cancer cells with present challenges and future directions

Cancer is one of the most leading causes of death and a major public health problem, universally. According to accumulated data, annually, approximately 8.5 million people died because of the lethality of cancer. Recently, a novel RNA domain-containing endonuclease-based genome engineering technology, namely the clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein-9 (Cas9) have been proved as a powerful technique in the treatment of cancer cells due to its multifunctional properties including high specificity, accuracy, time reducing and cost-effective strategies with minimum off-target effects. The present review investigates the overview of recent studies on the newly developed genome-editing strategy, CRISPR/Cas9, as an excellent pre-clinical therapeutic option in the reduction and identification of new tumor target genes in the solid tumors. Based on accumulated data, we revealed that CRISPR/Cas9 significantly inhibited the robust tumor cell growth (breast, lung, liver, colorectal, and prostate) by targeting the oncogenes, tumor-suppressive genes, genes associated to therapies by inhibitors, genes associated to chemotherapies drug resistance, and suggested that CRISPR/Cas9 could be a potential therapeutic target in inhibiting the tumor cell growth by suppressing the cell-proliferation, metastasis, invasion and inducing the apoptosis during the treatment of malignancies in the near future. The present review also discussed the current challenges and barriers, and proposed future recommendations for a better understanding.

The broad-spectrum antiviral recommendations for drug discovery against COVID-19

Despite to outbreaks of highly pathogenic beta and alpha coronaviruses including severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and human coronavirus, the newly emerged 2019 coronavirus (COVID-19) is considered as a lethal zoonotic virus due to its deadly respiratory syndrome and high mortality rate among the human. Globally, more than 3,517,345 cases have been confirmed with 243,401 deaths due to Acute Respiratory Distress Syndrome (ARDS) caused by COVID-19. The antiviral drug discovery activity is required to control the persistence of COVID-19 circulation and the potential of the future emergence of coronavirus. However, the present review aims to highlight the important antiviral approaches, including interferons, ribavirin, mycophenolic acids, ritonavir, lopinavir, inhibitors, and monoclonal antibodies (mAbs) to provoke the nonstructural proteins and deactivate the structural and essential host elements of the virus to control and treat the infection of COVID-19 by inhibiting the viral entry, viral RNA replication and suppressing the viral protein expression. Moreover, the present review investigates the epidemiology, diagnosis, structure, and replication of COVID-19 for better understanding. It is recommended that these proteases, inhibitors, and antibodies could be a good therapeutic option in drug discovery to control the newly emerged coronavirus.HighlightsCOVID-19 has more than 79.5% identical sequence to SARS-CoV and a 96% identical sequence of the whole genome of bat coronaviruses.Acute respiratory distress syndrome (ARDS), renal failure, and septic shock are the possible clinical symptoms associated with COVID-19.Different antivirals, including interferons, ribavirin, lopinavir, and monoclonal antibodies (mAbs) could be the potent therapeutic agents against COVID-19.The initial clinical trials on hydroquinone in combination with azithromycin showed an admirable result in the reduction of COVID-19.The overexpression of inflammation response, cytokine dysregulation, and induction of apoptosis could be an well-organized factors to reduce the pathogenicity of COVID-19.

Periodic Bicontinuous Structures Formed on the Top Surface of Asymmetric Triblock Terpolymer Thick Films

The combination of the nonsolvent-induced phase separation (NIPS) process with a solvent vapor annealing (SVA) treatment is used to produce asymmetric and hydrophobic thick films having different long-range ordered network nanostructures, which are inaccessible via currently available membrane fabrication methods. We show that the disordered phase generated by NIPS on the material top surface can be transformed into a highly ordered bicontinuous network nanostructure during the SVA process without disrupting the substructure morphology. For instance, by using a straightforward blending approach, either a triply periodic alternating diamond (D^A) structure or a core-shell perforated lamellar (PL) phase was demonstrated on the skin layer of fully hydrophobic poly(1,1-dimethyl silacyclobutane)-block-polystyrene-block-poly(methyl methacrylate) (PDMSB-b-PS-b-PMMA) thick films. Such a material fabrication method, enabling the formation of a sponge-like substructure topped by a network phase having an excellent long-range order, provides an appealing strategy to facilitate the manufacture of next-generation membranes at large scale since these bicontinuous morphologies obviate the need of the nanochannel alignment.

Core-Shell Double Gyroid Structure Formed by Linear ABC Terpolymer Thin Films

The synthesis and self-assembly in thin-film configuration of linear ABC triblock terpolymer chains consisting of polystyrene (PS), poly(2-vinylpyridine) (P2VP), and polyisoprene (PI) are described. For that purpose, a hydroxyl-terminated PS-b-P2VP (45 kg mol^-1 ) building block and a carboxyl-terminated PI (9 kg mol^-1 ) are first separately prepared by anionic polymerization, and then are coupled via a Steglich esterification reaction. This quantitative and metal-free catalyst synthesis route reveals to be very interesting since functionalization and purification steps are straightforward, and well-defined terpolymers are produced. A solvent vapor annealing (SVA) process is used to promote the self-assembly of frustrated PS-b-P2VP-b-PI chains into a thin-film core-shell double gyroid (Q²³⁰ , space group: Ia3¯d) structure. As terraces are formed within PS-b-P2VP-b-PI thin films during the SVA process under a CHCl₃ vapor, different plane orientations of the Q²³⁰ structure ((211), (110), (111), and (100)) are observed at the polymer-air interface depending on the film thickness.

Straightforward Integration Flow of a Silicon-Containing Block Copolymer for Line-Space Patterning

A promising alternative for the next-generation lithography is based on the directed self-assembly of block copolymers (BCPs) used as a bottom-up tool for the definition of nanometric features. Herein, a straightforward integration flow for line-space patterning is reported for a silicon BCP system, that is, poly(1,1-dimethylsilacyclobutane)-b-poly(styrene) (PDMSB-b-PS), able to define sub 15 nm features. Both in-plane cylindrical (L₀ = 20.7 nm) and out-of-plane lamellar structures (L₀ = 23.2 nm) formed through a rapid thermal annealing-10 min at 180 °C-were successfully integrated using graphoepitaxy to provide a long-range ordering of the BCP structure without the use of underlayers or top coats. Subsequent deep transfer into the silicon substrate using the hardened oxidized PDMSB domains as a mask is demonstrated. Combining a rapid self-assembly behavior, straightforward integration, and an excellent etching contrast, PDMSB-b-PS may become a material of choice for the next-generation lithography.

Templated Sub-100-nm-Thick Double-Gyroid Structure from Si-Containing Block Copolymer Thin Films

The directed self-assembly of diblock copolymer chains (poly(1,1-dimethyl silacyclobutane)-block-polystyrene, PDMSB-b-PS) into a thin film double gyroid structure is described. A decrease of the kinetics of a typical double-wave pattern formation is reported within the 3D-nanostructure when the film thickness on mesas is lower than the gyroid unit cell. However, optimization of the solvent-vapor annealing process results in very large grains (over 10 µm²) with specific orientation (i.e., parallel to the air substrate) and direction (i.e., along the groove direction) of the characteristic (211) plane, demonstrated by templating sub-100-nm-thick PDMSB-b-PS films.

Highly Ordered Nanoring Arrays Formed by Templated Si-Containing Triblock Terpolymer Thin Films

Laterally ordered nanorings with a periodicity of 38 nm are produced from the directed self-assembly of poly(1,1-dimethylsilacyclobutane)-block-polystyrene-block-poly(methyl methacrylate) thin films on topographically patterned substrates. Such nanoscale arrays with vertically oriented rings are highly desired in technological applications including memory using magnetic recording, metamaterial, waveguide, etc.

Investigation of Dielectric Properties of Polymers and their Discrimination Using Terahertz Time-Domain Spectroscopy with Principal Component Analysis

Polymers are among the most commonly used materials in our everyday life. They are generally transparent to terahertz (THz) radiation, but are quite difficult to differentiate using optical techniques as few or no characteristic features exist in the spectral range of <2.0 THz for small and portable radiation systems. In this work, we report experimental measurement of refractive indices and absorption coefficients of styrene acrylonitrile (SAN) and Bakelite in the spectral range of 0.2-2.0 THz for the first time. Additionally, we demonstrate that by combining principle component analysis (PCA) with THz time-domain spectroscopy one can differentiate such polymers. In this analysis, the first three principle components PC1, PC2, and PC3 depict >94% variance with a distribution of 72.45%, 11.52%, and 9.38%, respectively.

Flexible, Low Cost, and Platinum-Free Counter Electrode for Efficient Dye-Sensitized Solar Cells

A platinum-free counter electrode composed of surface modified aligned multiwalled carbon nanotubes (MWCNTs) fibers was fabricated for efficient flexible dye-sensitized solar cells (DSSCs). Surface modification of MWCNTs fibers with simple one step hydrothermal deposition of cobalt selenide nanoparticles, confirmed by scanning electron microscopy and X-ray diffraction, provided a significant improvement (∼2-times) in their electrocatalytic activity. Cyclic voltammetry and electrochemical impedance spectroscopy suggest a photoelectric conversion efficiency of 6.42% for our modified fibers, higher than 3.4% and 5.6% efficeincy of pristine MWCNTs fiber and commonly used Pt wire, respectively. Good mechanical and performance stability after repeated bending and high output voltage for in-series connection suggest that our surface modified MWCNTs fiber based DSSCs may find applications as flexible power source in next-generation flexible/wearable electronics.

Is Interarterial Course a Requisite for Ischemia in Anomalous Origin of Coronary Arteries?

Anomalous origin of the left main coronary artery from the noncoronary sinus (LCANS) is a rare variant of anomalous aortic origin of a coronary artery that is not characterized by an interarterial course. Despite the absence of an interarterial course, there are rare reports of LCANS presenting with sudden death, life-threatening arrhythmia, exercise-induced myocardial ischemia, premature ventricular contractions, and syncope. We report a patient with LCANS presenting with acute myocardial infarction who recovered completely with emergent surgical unroofing of the coronary artery.

Archimedean Tilings and Hierarchical Lamellar Morphology Formed by Semicrystalline Miktoarm Star Terpolymer Thin Films

3-Miktoarm star terpolymer architecture provides a window of opportunity in the design of complex "three-colored" patterns at the nanometer scale. Here, the directed self-assembly (DSA) of 3-miktoarm star terpolymer (poly(1,1-dimethyl silacyclobutane)-arm-polystyrene-arm-poly(d,l-lactide acid)) (PDMSB-arm-PS-arm-PLA, noted hereafter 3 μ-DSL) into a hierarchical lamellar morphology is described. Excellent orientational order has been achieved by templating the asymmetric hierarchical lamellar morphology with topographical substrates. Increasing the PLA volume fraction leads to the formation of a hexagonal [6.6.6] Archimedean tiling which coexists with a metastable square symmetry [4.8.8] tiling stabilized by the step between terraces. Stability of the [6.6.6] tiling over the [4.8.8] one is also demonstrated with GISAXS measurements.

Laterally Ordered Sub-10 nm Features Obtained From Directed Self-Assembly of Si-Containing Block Copolymer Thin Films

Laterally ordered sub-10 nm features are produced from the directed self-assembly of poly(1,1-dimethyl silacyclo-butane)-block-poly(methyl methacrylate) (PDMSB-b-PMMA) thin films on sinusoidal azobenzene-containing patterns. The use of sinusoidal surface relief grating enables the formation of very large grain areas (over several µm(2) ) consisting of out-of-plane PMMA cylinders.

Scanning electron microscopy analysis of hair index on Karachi's population for social and professional appearance enhancement

OBJECTIVE

Hair texture, appearance and pigment play an important role in social and professional communication and maintaining an overall appearance. This study was especially designed for morphological assessment of hair damage caused to Karachi's population due to natural factors and cosmetic treatments using scanning electron microscopy (SEM) technique.

METHODS

Hair samples under the study of synthetic factor's effect were given several cosmetic treatments (hot straightened, bleached, synthetic dyed and henna dyed) whereas samples under natural factor's effect (variation in gender, age and pigmentation) were left untreated. Morphological assessment was performed using SEM technique. Results obtained were statistically analysed using minitab 16 and spss 18 softwares.

RESULTS

Scanning electron microscopy images revealed less number of cuticular scales in males than females of same age although size of cuticular scales was found to be larger in males than in females. Mean hair index of white hair was greater than black hair of the same head as it is comparatively newly originated. Tukey's method revealed that among cosmetic treatments, bleaching and synthetic henna caused most of the damage to the hair.

CONCLUSION

Statistical evaluation of results obtained from SEM analysis revealed that human scalp hair index show morphological variation with respect to age, gender, hair pigmentation, chemical and physical treatments. Individuals opting for cosmetic treatments could clearly visualize the extent of hair damage these may cause in long run.

Sub-10 nm features obtained from directed self-assembly of semicrystalline polycarbosilane-based block copolymer thin films

Highly-ordered arrays with sub-10 nm features are produced with topographical-directed self-assembly of low-molecular-weight poly(1,1-dimethyl silacyclobutane)-block-poly(methyl methacrylate). This system turns out to be of high interest for lithographic applications since the domain orientation is solely controlled through the polymer layer thickness, while the promotion of the microphase separation is obtained by a short thermal annealing process under mild conditions.

A well-defined polyelectrolyte and its copolymers by reversible addition fragmentation chain transfer (RAFT) polymerization: synthesis and applications

Controlled polymerization and self-assembly of novel block copolymer electrolytes.

Aggregate Exposure and Cumulative Risk Assessment--Integrating Occupational and Non-occupational Risk Factors

Occupational exposure limits have traditionally focused on preventing morbidity and mortality arising from inhalation exposures to individual chemical stressors in the workplace. While central to occupational risk assessment, occupational exposure limits have limited application as a refined disease prevention tool because they do not account for all of the complexities of the work and non-occupational environments and are based on varying health endpoints. To be of greater utility, occupational exposure limits and other risk management tools could integrate broader consideration of risks from multiple exposure pathways and routes (aggregate risk) as well as the combined risk from exposure to both chemical and non-chemical stressors, within and beyond the workplace, including the possibility that such exposures may cause interactions or modify the toxic effects observed (cumulative risk). Although still at a rudimentary stage in many cases, a variety of methods and tools have been developed or are being used in allied risk assessment fields to incorporate such considerations in the risk assessment process. These approaches, which are collectively referred to as cumulative risk assessment, have potential to be adapted or modified for occupational scenarios and provide a tangible path forward for occupational risk assessment. Accounting for complex exposures in the workplace and the broader risks faced by the individual also requires a more complete consideration of the composite effects of occupational and non-occupational risk factors to fully assess and manage worker health problems. Barriers to integrating these different factors remain, but new and ongoing community-based and worker health-related initiatives may provide mechanisms for identifying and integrating risk from aggregate exposures and cumulative risks from all relevant sources, be they occupational or non-occupational.

Application of pharmacokinetic modelling for 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure assessment

Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and mono- and non-ortho polychlorinated biphenyls (dioxin-like PCBs) are identified as a family or group of organic compounds known as 'dioxins' or dioxin-like chemicals (DLCs). The most toxic member of this group is 2,3,7,8-tetrachlorodibenzo-(p)-dioxin (TCDD). Historically, DLCs have caused a variety of negative human health effects, but a disfiguring skin condition known as chloracne is the only health effect reported consistently. As part of translational research to make computerized models accessible to health risk assessors, the Concentration- and Age-Dependent Model (CADM) for TCDD was recoded in the Berkeley Madonna simulation language. The US Agency for Toxic Substances and Disease Registry's computational toxicology laboratory used the recoded model to predict TCDD tissue concentrations at different exposure levels. The model simulations successfully reproduced the National Health and Nutrition Examination Survey (NHANES) 2001-2002 TCDD data in age groups from 6 to 60 years and older, as well as in other human datasets. The model also enabled the estimation of lipid-normalized serum TCDD concentrations in breastfed infants. The model performed best for low background exposures over time compared with a high acute poisoning case that could due to the large dose and associated liver toxicity. Hence, this model may be useful for interpreting human biomonitoring data as a part of an overall DLC risk assessment.

Preparation of water-free PEDOT dispersions in the presence of reactive polyisoprene stabilizers

Poly(3,4-ethylenedioxythiophene) nanoparticles with narrow size distribution were prepared in organic dispersant media in the presence of both iron(III) dodecylbenzenesulfonate {Fe(DBS)3}-acting as both an oxidant and a stabilizer-and ω-functionalized polyisoprenes (ω-R-PI) as costabilizers. The effects of the solvent nature and concentration of Fe(DBS)3 on the size and morphology of the PEDOT particles were first studied in the absence of costabilizer. Second, the effects of the molar mass, concentration, and nature of the functional end group of the polyisoprene costabilizer were investigated. PEDOT nano-objects were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and conductivity measurements.

Physiologically based pharmacokinetic (PBPK) tool kit for environmental pollutants--metals

The Agency for Toxic Substances and Disease Registry (ATSDR) is mandated by the US Congress to identify significant human exposure levels, develop methods to determine such exposures, and design strategies to mitigate them. Physiologically based pharmacokinetic (PBPK) models are increasingly being used to evaluate toxicity of environmental pollutants through multiple exposure pathways. As part of its translational research project, ATSDR is developing a human 'PBPK model tool kit' that consists of a series of published models re-coded in a common simulation language. The tool kit currently consists of models, at various stages of development, for priority environmental contaminants including solvents and persistent organic pollutants. Presented here are results of translational activities of re-coding models for cadmium, mercury, and arsenic. As part of this work, following re-coding each new model was evaluated for fidelity followed by sensitivity analysis. Good agreement was generally obtained for all three models when predictions of original and re-coded model simulations were compared. Also presented is an application of the cadmium toxicokinetic model to interpret biomonitoring data from the National Health and Nutrition Examination Survey (NHANES). The PBPK tool kit will enable ATSDR scientists to perform simulations of exposures from contaminated environmental media at sites of concern and to better interpret site-specific biomonitoring data.

Synthesis of polyaniline nano-objects using poly(vinyl alcohol)-, poly(ethylene oxide)-, and poly[(N-vinyl pyrrolidone)-co-(vinyl alcohol)]-based reactive stabilizers

Well-defined polyaniline (PANI) nano-objects (e.g., spheres, peanuts, rice grains, corals, and fibers) were prepared by aniline dispersion polymerization in aqueous media in the presence of various reactive polymer stabilizers (i.e., poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), and poly[(N-vinyl pyrrolidone)-co-(vinyl alcohol)] (PNVP-co-PVA)). It was found that the shape, size, and conductivity of resulting PANI nanostructures depended on the acidic conditions along with the nature, molecular weight, and functionality of the reactive stabilizer. PANI samples were analyzed by X-ray photoelectron spectroscopy (XPS), dynamic scanning calorimetry (DSC), thermogravimetric analysis (TGA), UV-visible and FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and conductivity measurements. PANI samples show conductivities between 5 x 10(-3) to 5 x 10(-1) S/cm depending upon the experimental conditions. The best conductivities were obtained when aniline was polymerized in a mixture of DMSO and water (2:3) in the presence of PEO- or PNVP-co-PVA-based reactive stabilizers.

Remicade as TNF Suppressor in Patients with Myelodysplastic Syndromes

Remicade, a chimeric human-murine monoclonal antibody capable of neutralizing tumor necrosis factor alpha was given to 37 low-risk myelodysplastic syndromes (MDS) patients in two cohorts; 5 and 10 mg/kg intravenously every 4 weeks for 4 cycles. Median age was 68 years, 33 had primary MDS, 14 had refractory anemia (RA), 14 RA with ringed sideroblasts, 9 RA with excess blasts. Nine patients stopped therapy prior to completing 4 cycles, 3 from cohort 1 and 6 from cohort 2 and response was evaluated using the International Working Group criteria in 28 patients who completed the 4 cycles. Six patients showed disease progression, 14 had stable disease and 8 showed hematologic responses, 3/15 (20%) in cohort 1 and 5/13 (38%) in cohort 2. Two patients had multi-lineage responses, 2 had > 100% increase in absolute neutrophils, 1 had > 1 gm/dl increase in hemoglobin, 1 had reduction in blasts from 7% to 1%, and 2 had minor cytogenetic responses (> 50% reduction in + 8 and 20q-metaphases respectively). We conclude that Remicade may have a variety of activities in low risk MDS patients, is well tolerated with a high patient compliance, and may be considered for combination therapy in the future.

Phase II study of topotecan and thalidomide in patients with high-risk myelodysplastic syndromes

This phase II trial investigated the safety and preliminary efficacy of a topotecan/thalidomide combination therapy in patients with myelodysplastic syndrome who had refractory anemia with excess blasts (RAEB), RAEB with transformation, or chronic myelomonocytic anemia. Patients received three 21-day cycles of topotecan 1.25 mg/m(2) on days 1-5, which was repeated for two additional cycles in patients whose bone marrow blast percentages did not decrease. Oral thalidomide was then started at 100 mg/day (with the dose escalated up to 300 mg/day if well tolerated) for up to 1 year. Patients were monitored throughout the trial for hematologic and clinical adverse events, and efficacy was assessed using International Working Group (IWG) criteria. Forty-five patients, mostly elderly (median age 68 years; range 52-79 years), were enrolled. Therapy was generally well tolerated compared to high-dose chemotherapy. Three patients died from disease progression/infections during topotecan therapy, and four patients discontinued topotecan because of high-grade neutropenia (two patients), syncope (one patient), or hip surgery (one patient). Of 24 patients who received thalidomide, three discontinued because of treatment-related toxicity. Thirty-eight patients were evaluable for response: nine (24%) had hematologic improvement and 13 (34%) had stable disease. Responses occurred in patients with all disease subtypes. Six patients achieved transfusion independence, and one patient had a trilineage response. Approximately one-third of the patients had decreases in bone marrow blasts of 50%. Therefore, a topotecan and thalidomide combination therapy is promising, although further studies are needed to determine the optimum doses and schedule.

Synthesis of calibrated poly(3,4-ethylenedioxythiophene) latexes in aqueous dispersant media

The synthesis of spherical poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles with a narrow size distribution was achieved in a dispersant aqueous medium. Various oxidants such as ammonium persulfate, iron(III) p-toluenesulfonate, and iron(III) trichloride were tested. A series of end-functionalized poly(ethylene oxide) (PEO) such as alpha-(3,4-ethylenedioxythiophene) PEO, alpha-( N-methyl pyrrole) PEO, alpha-(fluorene) PEO, alpha,omega-( N-methyl pyrrole) PEO, alpha,omega-(thiophene) PEO, and alpha,omega-(fluorene) PEO were compared as reactive stabilizers. The molar mass and the functionality of these reactive PEOs were found to be important parameters with respect to the control of particle size and size distribution. PEDOT samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), size exclusion chromatography (SEC), and conductivity measurements.