Low Void Volume Research Articles

Rate and temperature dependent compaction-creep-recovery and void analysis of compression molded prepregs

This study investigates the compaction-creep response of a glass/epoxy prepreg system at different temperatures, pressures, and compaction speeds, using a compaction fixture with heated platens, housed in-situ in an X-ray computed tomography (XCT) machine. It has been shown that by increasing the compaction speed from 0.1 mm/min to 1 mm/min, the total strain, the percentage of compaction creep and the resulting permanent deformation increased for all of the temperature and pressure conditions considered in this study. It was noted that for all compaction speeds and pressures, the percentage of compaction-creep increases from 25 °C up to 55 °C and then decreases with further increases in temperature. A decrease in creep deformation with post creep-thickness recovery, due to the resin squeezing out from the prepreg, was observed at higher temperatures. The void content in the post-creep, fully cured laminates was determined using an analytical model, the results of which were compared with XCT-developed geometrical models. Good agreement between both approaches was observed, with differences in void content results of less than 12% being recorded. The optimum process parameters (55 °C, 0.3 MPa and 0.5 mm/min) were identified in compression molded prepreg samples to choose the first isothermal dwell period . The combination of these process parameters resulted in moderate levels of compaction-creep and permanent deformation as well as a low void volume fraction in the test samples. • Rate dependent thermo-mechanical compaction-creep tests were performed on uncured glass/epoxy prepreg samples. • Percentage of compaction-creep and permanent deformation are found to be increasing with the increase of compaction speed. • Void volume fraction was determined in cured samples using analytical and XCT-aided geometrical models and compared. • Normal distribution statistical analysis was employed to study the size and shape of individual voids.

Design and validation of a novel operando spectroscopy reaction chamber for chemoresistive gas sensors

This work deals with the experimentation of a new ambient chamber for the use in diffuse reflectance Fourier infrared spectroscopy studies on chemoresistive gas sensors in operando condition. This system can support the investigation of gas–solid phase reactions at the sensor's surface during its operation, providing a reliable characterization tool that can be easily reproduced, implemented and adapted for several types of gas sensing devices. A deepened investigation was carried out: design of the chamber and the coupled acquisition system with temperature and humidity monitoring, 3D modelling, fluid dynamics study via residence time distribution analysis, and temperature gradient evaluation. Then, the system was validated in the case of a SnO2 sensor exposed to hydrogen gas flow. The new developed low void-volume gas sensing system is easy to machine, to use, to maintain, and it can be employed with solid-state gas sensors with an active area of 1 mm2 and operating temperatures up to 650 °C. In order to improve and facilitate the spectra acquisition, the system is equipped with precision staging and alignment, and it is fully compatible with Harrick Scientific's diffuse reflectance accessory.

Characteristic evaluation and finite element analysis of glass fiber/recycled polyester thermoplastic composites by cross-sectional shape of glass fiber

In this paper, properties of glass fiber-reinforced thermoplastic polymers (GFRTP) were evaluated using recycled polyester (rPET) for injection molding bicycle frame. The effect on thermal and mechanical properties of rPET reinforced glass chop fiber according to fiber cross section and fiber content ratio were studied. The crystallization temperature of glass fiber (GF)/rPET, a glass fiber added thermoplastic composite, was higher than the crystallization temperature of rPET pellet without a glass fiber, and the shape of the exothermic curve was sharper. Mechanical characteristics of a GF/rPET thermoplastic composites has been increased by increasing fiber contents, than above a certain level did not longer increased. And mechanical properties of flat glass fiber reinforced rPET with low void volume were most excellent. In order to prove the validity of the experimental results, finite element analysis of thermoplastic composite was performed by Digimat and Abaqus to compare the experimental values according to the cross sectional shape and volume fraction of glass fiber. The results of finite element analysis showed a similar tendency between the experimental results and the analysis results.

High‐Density Organic Electro‐Optic Crystals for Ultra‐Broadband THz Spectroscopy

AbstractUltra‐broadband THz photonics covering the 0.3–20 THz range provides a very attractive foundation for a wide range of basic research and industrial applications. However, the lack of ultra‐broadband THz devices has yet to be overcome. In this work, high‐density organic electro‐optic crystals are newly developed for efficient THz wave generation in a very broad THz spectral range and are successfully used for a broadband THz time‐domain spectroscopy. The new organic THz generator crystals, namely the OHP‐TFS crystals, have very low void volume, high density, and are shown to cover the ultra‐broadband THz spectrum up to about 15 THz, which cannot be easily accessed with the more widely used inorganic‐based THz generators. In addition to the very favorable broadband properties, the generated THz electric‐field amplitude at the pump wavelength of 1560 nm is about 40 times higher than that generated by a commercial inorganic THz generator (ZnTe crystal). By using the newly developed OHP‐TFS as generation crystal in a compact table‐top all‐organic THz time‐domain spectrometer based on a low‐cost telecom fiber laser, the optical characteristics of a model material are successfully determined in the broad 1.5–12.5 THz range with high accuracy.

Post-column reaction with a 3D-printed two-stage microreactor and flame ionization detection for carbon compound independent response in fast gas chromatography

Fast gas chromatography that leverages the high chromatographic efficiency of narrow bore capillary column technology and temperature programming was successfully integrated with a third-generation low void-volume, 3D-printed two-stage microreactor. Effective management of extra-column effect and the capability to perform post-column backflushing were achieved with the incorporation of a recently commercialized, electronically controlled pneumatic switching device and a deactivated metal three-way microdevice.With this configuration, narrow bore capillary columns having internal diameters between 0.10 and 0.15 mm can be employed to produce chromatographic peaks in the domain of fast gas chromatography, with peak widths at half-height ranging from 0.42 s to 0.92 s for probe compounds having k over a range from 1.7 for toluene to 60 with the last analyte (nC44) eluted in less than 12 min.The carbon independent response capability of the 3D-printed microreactor affords unique and advantaged differentiators, for instance, conducting measurement of the target analytes using one single carbon-containing compound for calibration with an acceptable accuracy of ±10%, achieving a higher degree of accuracy by eliminating the need for multi-level and multi-compound calibration, and improving sensitivity for compounds that are not efficiently ionized by flame ionization detection.Using this platform, repeatability of retention times for 14 probe compounds was less than 0.1% RSD (n = 10), and less than 1.0% RSD (n = 10) for area counts. The utility of the analytical approach was illustrated with relevant, challenging applications.

Design, modelling, and application of a low void-volumein situdiffuse reflectance spectroscopic reaction cell for transient catalytic studies

A new low void-volumein situreaction cell enables application of modulation excitation-phase sensitive detection-diffuse reflectance Fourier transform spectroscopy (ME-PSD-DRIFTS).

Application of modulation excitation-phase sensitive detection-DRIFTS forin situ/operando characterization of heterogeneous catalysts

A new more general method and guidelines for the implementation of modulation excitation-phase sensitive detection-diffuse reflectance Fourier transform spectroscopy (ME-PSD-DRIFTS).

Sorbent, device, matrix and application in microextraction by packed sorbent (MEPS): A review.

Microextraction by packed sorbent (MEPS) is a new miniaturized form of solid-phase extraction and it is a green sample pretreatment technology. MEPS has been widely accepted and used by several research groups online or offline as a sample preparation technique before instrument analysis. MEPS reduces the sample handling time and organic solvent consumption. MEPS is suitable for small sample volumes and can easily be connected with different chromatographic techniques without modification. The sorbent bed in MEPS is integrated into a liquid handling syringe that allows for low void volume sample manipulations either manually or in combination with laboratory robotics. MEPS is a simple, fast and robust sample preparation technique with several advantages, miniaturization, automation, fast operation course, on-line coupling with analytical instruments and low-cost operation with less solvent and low sample consumption. Sorbent type, device, and matrix are important factors in MEPS research and applications. The performance of MEPS has recently been illustrated by online with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry assays for pharmaceutical, environmental, and food analyses. This paper deals with MEPS device-optimized sorbent, sample matrix, and application. The progress and potential development of the technique are also discussed.

A unified criterion for the growth and coalescence of microvoids

A yield criterion is developed which unifies void growth and void coalescence theories. Standard void growth theory assumes that plastic flow is diffuse, if not prevalent everywhere within the matrix of the elementary cell considered. On the other hand, void coalescence theory assumes states of post-localized plasticity whereby plastic flow is restricted to intervoid ligaments. The new theory accommodates both scenarios through some appropriate choice of microscopic velocity fields. An important implication for actual evolution problems is a seamless transition from void growth to void coalescence. This is in contrast with previous hybrid approaches whereby abrupt transitions are associated with the presence of unavoidable corners in the effective yield surface. More generally, the new criterion is applicable to describe yielding in porous metal plasticity for both low and high void volume fractions.

A Remodeled Protein Arginine Methyltransferase 1 (PRMT1) Generates Symmetric Dimethylarginine

Protein arginine methylation is emerging as a significant post-translational modification involved in various cell processes and human diseases. As the major arginine methylation enzyme, protein arginine methyltransferase 1 (PRMT1) strictly generates monomethylarginine and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA). The two types of dimethylarginines can lead to distinct biological outputs, as highlighted in the PRMT-dependent epigenetic control of transcription. However, it remains unclear how PRMT1 product specificity is regulated. We discovered that a single amino acid mutation (Met-48 to Phe) in the PRMT1 active site enables PRMT1 to generate both ADMA and SDMA. Due to the limited amount of SDMA formed, we carried out quantum mechanical calculations to determine the free energies of activation of ADMA and SDMA synthesis. Our results indicate that the higher energy barrier of SDMA formation (ΔΔG(‡) = 3.2 kcal/mol as compared with ADMA) may explain the small amount of SDMA generated by M48F-PRMT1. Our study reveals unique energetic challenges for SDMA-forming methyltransferases and highlights the exquisite control of product formation by active site residues in the PRMTs.

Prediction of free air space in initial composting mixtures by a statistical design approach

Free air space (FAS) is a physical parameter that can play an important role in composting processes to maintain favourable aerobic conditions. Aiming to predict the FAS of initial composting mixtures, specific materials proportions ranged from 0 to 1 were tested for a case study comprising industrial potato peel, which is characterized by low air void volume, thus requiring additional components for its composting.The characterization and prediction of FAS for initial mixtures involving potato peel, grass clippings and rice husks (set A) or sawdust (set B) was accomplished by means of an augmented simplex-centroid mixture design approach. The experimental data were fitted to second order Scheffé polynomials. Synergistic or antagonistic effects of mixture proportions in the FAS response were identified from the surface and response trace plots in the FAS response. Moreover, a good agreement was achieved between the model predictions and supplementary experimental data. Moreover, theoretical and empirical approaches for estimating FAS available in literature were compared with the predictions generated by the mixture design approach.This study demonstrated that the mixture design methodology can be a valuable tool to predict the initial FAS of composting mixtures, specifically in making adjustments to improve composting processes containing primarily potato peel.

Proteomic Analysis Reveals Diverse Classes of Arginine Methylproteins in Mitochondria of Trypanosomes

Arginine (arg) methylation is a widespread posttranslational modification of proteins that impacts numerous cellular processes such as chromatin remodeling, RNA processing, DNA repair, and cell signaling. Known arg methylproteins arise mostly from yeast and mammals, and are almost exclusively nuclear and cytoplasmic. Trypanosoma brucei is an early branching eukaryote whose genome encodes five putative protein arg methyltransferases, and thus likely contains a plethora of arg methylproteins. Additionally, trypanosomes and related organisms possess a unique mitochondrion that undergoes dramatic developmental regulation and uses novel RNA editing and mitochondrial DNA replication mechanisms. Here, we performed a global mass spectrometric analysis of the T. brucei mitochondrion to identify new arg methylproteins in this medically relevant parasite. Enabling factors of this work are use of a combination digestion with two orthogonal enzymes, an efficient offline two dimensional chromatography separation, and high-resolution mass spectrometry analysis with two complementary activations. This approach led to the comprehensive, sensitive and confident identification and localization of methylarg at a proteome level. We identified 167 arg methylproteins with wide-ranging functions including metabolism, transport, chaperoning, RNA processing, translation, and DNA replication. Our data suggest that arg methylproteins in trypanosome mitochondria possess both trypanosome-specific and evolutionarily conserved modifications, depending on the protein targeted. This study is the first comprehensive analysis of mitochondrial arg methylation in any organism, and represents a significant advance in our knowledge of the range of arg methylproteins and their sites of modification. Moreover, these studies establish T. brucei as a model organism for the study of posttranslational modifications.

Designing high-performance electrochemical energy-storage nanoarchitectures to balance rate and capacity

The impressive specific capacitance and high-rate performance reported for many nanometric charge-storing films on planar substrates cannot impact a technology space beyond microdevices unless such performance translates into a macroscale form factor. In this report, we explore how the nanoscale-to-macroscale properties of the electrode architecture (pore size/distribution, void volume, thickness) define energy and power performance when scaled to technologically relevant dimensions. Our test bed is a device-ready electrode architecture in which scalable, manufacturable carbon nanofoam papers with tunable pore sizes (5-200 nm) and thickness (100-300 μm) are painted with ~10 nm coatings of manganese oxide (MnOx). The quantity of capacitance and the rate at which it is delivered for four different MnOx-C variants was assessed by fabricating symmetric electrochemical capacitors using a concentrated aqueous electrolyte. Carbon nanofoam papers containing primarily 10-20 nm mesopores support high MnOx loadings (60 wt%) and device-level capacitance (30 F g(-1)), but the small mesoporous network hinders electrolyte transport and the low void volume restricts the quantity of charge-compensating ions within the electrode, making the full capacitance only accessible at slow rates (5 mV s(-1)). Carbon nanofoam papers with macropores (100-200 nm) facilitate high rate operation (50 mV s(-1)), but deliver significantly lower device capacitance (13 F g(-1)) as a result of lower MnOx loadings (41 wt%). Devices comprising MnOx-carbon nanofoams with interconnecting networks of meso- and macropores balance capacitance and rate performance, delivering 33 F g(-1) at 5 mV s(-1) and 23 F g(-1) at 50 mV s(-1). The use of carbon nanofoam papers with size-tunable pore structures and thickness provides the opportunity to engineer the electrode architecture to deliver scalable quantities of capacitance (F cm(-2)) in tens of seconds with a single device.

Survival of Hepatitis C Virus in Syringes: Implication for Transmission among Injection Drug Users

We hypothesized that the high prevalence of hepatitis C virus (HCV) among injection drug users might be due to prolonged virus survival in contaminated syringes. We developed a microculture assay to examine the viability of HCV. Syringes were loaded with blood spiked with HCV reporter virus (Jc1/GLuc2A) to simulate 2 scenarios of residual volumes: low void volume (2 microL) for 1-mL insulin syringes and high void volume (32 microL) for 1-mL tuberculin syringes. Syringes were stored at 4 degrees C, 22 degrees C, and 37 degrees C for up to 63 days before testing for HCV infectivity by using luciferase activity. The virus decay rate was biphasic (t1/2alpha= 0.4 h and t1/2beta = 28 hh). Insulin syringes failed to yield viable HCV beyond day 1 at all storage temperatures except 4 degrees , in which 5% of syringes yielded viable virus on day 7. Tuberculin syringes yielded viable virus from 96%, 71%, and 52% of syringes after storage at 4 degrees, 22 degrees, and 37 degrees for 7 days, respectively, and yielded viable virus up to day 63. The high prevalence of HCV among injection drug users may be partly due to the resilience of the virus and the syringe type. Our findings may be used to guide prevention strategies.

Development of a microfluidic confocal fluorescence detection system for the hyphenation of nano-LC to on-line biochemical assays

One way to profile complex mixtures for receptor affinity is to couple liquid chromatography (LC) on-line to biochemical detection (BCD). A drawback of this hyphenated screening approach is the relatively high consumption of sample, receptor protein and (fluorescently labeled) tracer ligand. Here, we worked toward minimization of sample and reagent consumption, by coupling nano-LC on-line to a light-emitting diode (LED) based capillary confocal fluorescence detection system capable of on-line BCD with low-flow rates. In this fluorescence detection system, a capillary with an extended light path (bubble cell) was used as a detection cell in order to enhance sensitivity. The technology was applied to a fluorescent enhancement bioassay for the acetylcholine binding protein, a structural analog of the extracellular ligand-binding domain of neuronal nicotinic acetylcholine receptors. In the miniaturized setup, the sensitive and low void volume LED-induced confocal fluorescence detection system operated in flow injection analysis mode allowing the measurement of IC50 values, which were comparable with those measured by a conventional plate reader bioassay. The current setup uses 50 nL as injection volume with a carrier flow rate of 400 nL/min. Finally, coupling of the detection system to gradient reversed-phase nano-LC allowed analysis of mixtures in order to identify the bioactive compounds present by injecting 10 nL of each mixture.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-010-4210-x) contains supplementary material, which is available to authorized users.

Proteomic expression profiling of Haemophilus influenzae grown in pooled human sputum from adults with chronic obstructive pulmonary disease reveal antioxidant and stress responses

BackgroundNontypeable Haemophilus influenzae colonizes and infects the airways of adults with chronic obstructive pulmonary disease, the fourth most common cause of death worldwide.Thus, H. influenzae, an exclusively human pathogen, has adapted to survive in the hostile environment of the human airways.To characterize proteins expressed by H. influenzae in the airways, a prototype strain was grown in pooled human sputum to simulate conditions in the human respiratory tract.The proteins from whole bacterial cell lysates were solubilized with a strong buffer and then quantitatively cleaned with an optimized precipitation/on-pellet enzymatic digestion procedure.Proteomic profiling was accomplished by Nano-flow liquid chromatography/mass spectroscopy with low void volume and high separation efficiency with a shallow, long gradient.ResultsA total of 1402 proteins were identified with high confidence, including 170 proteins that were encoded by genes that are annotated as conserved hypothetical proteins.Thirty-one proteins were present in greater abundance in sputum-grown conditions at a ratio of > 1.5 compared to chemically defined media.These included 8 anti-oxidant and 5 stress-related proteins, suggesting that expression of antioxidant activity and stress responses is important for survival in the airways.Four proteins involved in uptake of divalent anions and 9 proteins that function in uptake of various molecules were present in greater abundance in sputum-grown conditions.ConclusionsProteomic expression profiling of H. influenzae grown in pooled human sputum revealed increased expression of antioxidant, stress-response proteins and cofactor and nutrient uptake systems compared to media grown cells.These observations suggest that H. influenzae adapts to the oxidative and nutritionally limited conditions of the airways in adults with chronic obstructive pulmonary disease by increasing expression of molecules necessary for survival in these conditions.

183 ROLE OF MYOSIN LIGHT CHAIN PHOSPHORYLATION IN PARTIAL BLADDER OUTLET OBSTRUCTION: COMPENSATED VERSUS DECOMPENSATED

You have accessJournal of UrologyBladder and Urethra: Anatomy, Physiology and Pharmacology I1 Apr 2010183 ROLE OF MYOSIN LIGHT CHAIN PHOSPHORYLATION IN PARTIAL BLADDER OUTLET OBSTRUCTION: COMPENSATED VERSUS DECOMPENSATED Joseph Hypolite, Shaohua Chang, Stephen Zderic, Alan Wein, Stephan Butler, and Samuel Chacko Joseph HypoliteJoseph Hypolite Lansdowne, PA More articles by this author , Shaohua ChangShaohua Chang Glenolden, PA More articles by this author , Stephen ZdericStephen Zderic Philadelphia, PA More articles by this author , Alan WeinAlan Wein Philadelphia, PA More articles by this author , Stephan ButlerStephan Butler Philadelphia, PA More articles by this author , and Samuel ChackoSamuel Chacko Glenolden, PA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.239AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Benign prostatic hyperplasia (BPH) in men can lead to bladder outlet obstruction(BOO). We have reported previously that BOO in the rabbit model can be categorized into compensated and decompensated based on bladder function studies obtained from metabolic cage data and in vitro biochemical and physiological studies. The compensated group maintains their function close to normal whereas the decompensated group demonstrates higher frequency of urination and low void volume. The bladder dysfunction is also associated with changes in contractile and regulatory proteins which control myosin phosphorylation, and can affect force generation of the bladder smooth muscle. In the present study, we ask what role myosin light chain (MLC20) phosphorylation plays in BOO-induced compensation and decompensation at the resting level, and upon activation with carbachol (50μM) and KCl (125mM). METHODS Adult male New Zealand white rabbits were partially obstructed by surgical ligation of the urethra, and sham-operated rabbits served as controls. Metabolic cage data analysis was used to segregate bladders into compensated and decompensated groups based on the frequency of urination and void volume over a 24 hour period. In vitro muscle strip studies and two-dimensional gel electrophoresis were used to study contractile function and MLC20 phosphorylation, respectively, in sham-operated and two week obstructed rabbit bladders. RESULTS Decompensated bladders showed a significant reduction in maximum force, and the rate of force generation in response to both KCl (47%) and carbachol (41%) compared to compensated and sham bladders. Both the resting level of MLC20 phosphorylation (13%) and the level at maximum force generation (23%) were significantly less in decompensated bladders compared to sham and compensated bladders (23% at resting level and 36% at maximum force). There was no significant difference in the basal, or maximal phosphorylation level in response to KCl and carbachol between sham and compensated bladders. The mean weights of the bladders were, 2.2, 4.8 and 10.4 grams for sham, compensated and decompensated respectively. CONCLUSIONS Since MLC20 phosphorylation is the primary mechanism involved in smooth muscle contraction, the data suggests that the reduced levels of MLC20 phosphorylation both at rest and upon activation, in the decompensated bladders may be a major contributing factor to the contractile dysfunction seen in these bladders. © 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e73 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Joseph Hypolite Lansdowne, PA More articles by this author Shaohua Chang Glenolden, PA More articles by this author Stephen Zderic Philadelphia, PA More articles by this author Alan Wein Philadelphia, PA More articles by this author Stephan Butler Philadelphia, PA More articles by this author Samuel Chacko Glenolden, PA More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Sex Differences in Cystometry of Normal and Hypertensive Conscious Rat

Cystometry of the conscious rat is an effective method tostudy bladder function without compromising micturitionreflexes with anesthetics. This model can be influenced byinflammation, hormones and potentially strain of animal.Therefore, we examined whether gender has any impacton the micturition pattern of Sprague-Dawley (SD), WistarKyoto (WKY) and Spontaneously Hypertensive rat (SHR). Inthis study, recovery after surgery had a major impact on cystometryduring the early days of post-surgery. Void intervalswere shorter with very low void volume on the first day aftersurgery. However, there was a gradual increase in voidinterval and void volume from the second day onwards andwere stable on the fifth through seventh days post-surgery.Regarding strains, it was found that void volume and void intervalwere similar between SD and WKY rat. SHR, had a lowervoid volume with a shorter void interval than the WKY. Interestingly,the void interval in male rats, regardless of strain,was shorter compared to the females of the respective strain.It is concluded that a stable cystometric pattern is observedin the conscious SD rat after the fifth day of post-surgerywhich suggests that at least 1 week should be allowed afterbladder surgery to observe a stable cystometric data. Therewas a clear sex difference in the micturition pattern amongthe strains in that the frequency of micturition of the malewas higher than female SD, WKY and SHR. Studying the sexdifferences in the micturition pattern might improve understandingthe different pathophysiology of bladder control inmen and women.

Ultraporous Nanosheath Materials by Layer‐by‐Layer Deposition onto Co‐continuous Polymer‐Blend Templates

Porous polymer materials with interconnected porosity have recently received great attention due to their wide range of possible applications and the challenges they pose in preparation. Their potential applications range from use in the biomedical and pharmaceutical fields (tissue engineering and drug delivery) [1–3] to chromatographic materials, [4] to catalysis of chemical and biochemical reactions, [5] and to electronic devices. [6] For tissue-engineering applications, for instance, at least four different techniques for fabricating interconnected porous polymer substrates have been developed: fiber bonding of unwoven meshes, [7] solvent casting/particulate leaching, [8] gas foaming, [9] and phase separation. [10] However, every one of these approaches suffers from severe limitations including low levels of interconnectivity, low void volume, poor control of pore size and distribution, and difficulties in obtaining materials of reproducible porosities. Previously, we advanced an approach to preparing microporous materials based on the melt-blending of two immiscible polymers [11] and demonstrated that selective extraction of one of two components in a co-continuous mixture can result in a single-component structure of fully interconnected porosity with highly controlled porosity, morphology, and pore diameters ranging from 100 nm to hundreds of micrometers. [12,13] However, this method was found to be limited in the void volume that can be attained, and able to be used to prepare only relatively low-void-volume substrates (75%). Layer-by-layer (LbL) deposition is a simple and effective approach to deposit ultrathin and uniform molecular layers onto surfaces in which polyelectrolytes are adsorbed on an oppositely charged surface, reversing the surface charge and leaving it primed for the next deposition cycle. [14–16] Originally

Development of a large-volume, membrane-based injection system for gradient elution micro-liquid chromatography

A membrane unit which can be used to inject a large volume of sample solution was developed to facilitate reproducible and accurate gradient elution in micro-high-performance liquid chromatography (micro-HPLC). Since the membrane unit has a very low void volume, it facilitates the effective concentration of analytes in large sample volumes. Gradient elution micro-HPLC with the membrane unit allowed the efficient separation of n-alkyl benzoates, used as test samples, in a short time without marked gradient delay. In this study, the membrane unit could be loaded with up to 50 μg of n-hexyl benzoate, and more than 500 μL of sample solution could be applied. In about 50 chromatographic runs, the relative standard deviation (RSD) of the relative retention time of n-hexyl benzoate with respect to methyl benzoate was 0.530%.