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Introduction: Low back pain is one of the most common complaints in clinical practice with life time prevalence ranging from 65-80%. The annual prevalence of low back pain ranges from 15% to 45% but is largely dependent on population. Major cause of low back pain leading to severe morbidity throughout the world affecting mainly the young population is lumbar disc prolapse. Prolapsed intervertebral disc is an important cause of spondylogenic backache. Conservative treatment is often preferred for LDH, but patients who fail to respond to this are treated with surgery. Surgical treatment aims to remove the herniated nucleus pulposus to the largest extent possible to relieve nerve compression while minimizing spinal instability. Aim of the Study: The aim of this study was to assess the functional Outcome of open conventional discectomy among patients with prolapse lumbar intervertebral disc or lumbar herniated disk. Methods: This was a prospective observational study and was conducted in the Department of Orthopaedics Surgery, Square Hospitals Ltd, Dhaka, Bangladesh during the period from January 2008 to December 2020. We included 300 patients with prolapse lumbar intervertebral disc undergoing open conventional discectomy in our study. Result: In our study we found majority (36%) of our patients was aged 41-50 years and most of our study patients were male (70%) compared to female (30%). We found the mean age was 44.73 ± 8.9 years. Among all patients 78% had lower lumber problem & 22% had upper lumber problem. Most of our patients (44.5%) had L4-L5 level, followed by 31.5% had L5-S1 level. We found the mean vas score for leg pain and back pain in preoperative period significantly reduced at postoperative 2nd week, 3rd month, 6th month and 1st year. The mean ODI score was 56.24 ± 4.18 in preoperative period. At postoperative 1st year follow up the mean score significantly reduced to 3.26 ± 2.64 in our study. Majority (37%) of our patients had good outcome, followed ....

In Bangladesh, the peaking power plants that serve the peak time loads use conventional fossil fuels for power generation. These power stations remain idle for a good part of their operating life, which therefore results in a high overhead cost. Continuous integration of renewables into the grid is increasing the dependency on these, so far, feasibility of no other less-expensive options has been studied. In this context, this paper aims to analyze the financial feasibility of different alternative options. Three possible options were analyzed and the levelized cost of energy (LCOE) was compared with that of conventional peaking power plants. It was found that Battery-based storage systems are not financially feasible at this moment, while the nation’s lone hydro power plant promises financial feasibility if solar PV driven pumped hydro storage is implemented. We also report that if the nation continues to add solar PV power stations even with costly peaking power plants using traditional fuels, this hybrid option was counter intuitively found to be financially feasible.

Guanidinium is one of nature's strongest denaturants and is also a motif that appears in several interfacial contexts such as the RGD sequence involved in cell adhesion, cell penetrating peptides, and antimicrobial molecules. It is important to quantify the origin of guanidinium's ion-specific interactions so that its unique behavior may be exploited in synthetic applications. The present work demonstrates that guanidinium ions can both break and form strongly associating ion complexes in a context-dependent way. These insights into guanidinium's behavior are elucidated using polyelectrolyte complexes (PECs), where interpolymer ion pairs between oppositely charged polymers play an important role in determining material stability. Different polycation-polyanion combinations can span a large range of association affinities, where more strongly associating complexes can remain insoluble in concentrated salt solutions and in extreme pH conditions. This high stability is desirable in several application contexts for PECs, but also renders them challenging to process and, therefore, to study since they cannot be dissolved into polymer solutions. Here we demonstrate that guanidinium salts are very effective in dissolving the poly(styrenesulfonate)/poly(allylamine) (PSS:PAH) complex, which has one of the highest reported polycation-polyanion association affinities. We also demonstrate the importance of charge identity in complexation phenomena by functionalizing guanidinium directly into poly(allylamine), resulting in a complex that remains stable under highly denaturing conditions. The model system of PSS:PAH is used to glean insights into guanidinium's denaturing activity, as well as to broadly comment on the nature of ion-specific interactions in charged macromolecules.

Polyelectrolyte complex (PEC) materials show promise in the development of tunable membranes for aqueous and organic solvent separations, as well as in the creation of surface layers for fouling control. In this study, we developed a polyelectrolyte complex (PEC) functionalized by negatively charged carboxymethyl chitosan (CMC-) and positively charged quaternized chitosan (QC+) to tailor its surface properties and antibacterial efficacy. CMC- and QC+ were prepared and characterized using FT-IR and 1H NMR, which confirmed the presence of the carboxymethyl group and trimethylammonium group in CMC- and QC+ with 65.6% and 83.9% substitution, respectively. The CMC- functionalized PEC (CMC-/PEC) and QC+ functionalized PEC materials (QC+/PEC) were evaluated for their stability in water, resistance to organic and inorganic adsorption, and antibacterial action against a model microorganism, Pseudomonas putida. The results showed no release of chitosan derivatives after adsorption, and CMC-/PEC and QC+/PEC exhibited charge-based, selective repulsion of model organic and inorganic substances. Moreover, the functionalized PEC surfaces displayed lower bacterial attachment due to their smoother surfaces as compared to the bare ceramic membrane and their antimicrobial properties. Among the PEC samples, CMC-/PEC had the lowest cell attachment, while QC+/PEC showed the highest attachment due to electrostatic attraction. The ceramic and bare PEC surfaces were negligibly bactericidal, while cell viability decreased to 34.4 ± 10.2% and 30.6 ± 8.2% with the CMC-/PEC and QC+/PEC surfaces, respectively. In the filtration experiments, the unmodified PEC and CMC-/PEC showed lower rates of flux decline due to organic fouling than did the bare ceramic or QC+/PEC due to electrostatic repulsion. Furthermore, PECs as protective layers promoted much higher flux recoveries than simply backwashing the uncoated membranes. This surface tunability, then, enhances the potential of PECs either as fouling resistant materials or as a method to create a sacrificial, protective layer on surfaces that once fouled can be dissolved and re-established.

[Image: see text] Quantitatively understanding the self-assembly of amphiphilic macromolecules at liquid–liquid interfaces is a fundamental scientific concern due to its relevance to a broad range of applications including bottom-up nanopatterning, protein encapsulation, oil recovery, drug delivery, and other technologies. Elucidating the mechanisms that drive assembly of amphiphilic macromolecules at liquid–liquid interfaces is challenging due to the combination of hydrophobic, hydrophilic, and Coulomb interactions, which require consideration of the dielectric mismatch, solvation effects, ionic correlations, and entropic factors. Here we investigate the self-assembly of a model block copolymer with various charge fractions at the chloroform–water interface. We analyze the adsorption and conformation of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) and of the homopolymer poly(2-vinylpyridine) (P2VP) with varying charge fraction, which is controlled via a quaternization reaction and distributed randomly along the backbone. Interfacial tension measurements show that the polymer adsorption increases only marginally at low charge fractions (

Additive manufacturing technology has recently created a very useful engineering option for prototyping a wide range of electronic devices owing to its intrinsic aspects of fast turn-around, accuracy, easier fabrication, and low implementation costs. Electrifi, a commercially available conductive filament has been lately reported by multiple researchers as a potential candidate for replacing traditional copper traces on printed circuit boards through additive manufacturing technologies. For the first time, this paper presents a completely 3D-printed conformal microstrip patch antenna. Using the fused filament fabrication method, the flexible conductive layers and the flexible non-conductive substrate of the antenna were additively manufactured using materials: Electrifi and NinjaFlex, respectively. Furthermore, for validation of the manufactured flexible prototype, a similar model was fabricated and tested where one of the trace layers made of Electrifi filament was replaced using a commercial adhesive copper foil. Overall, the reported fully 3D-printed flexible antenna shows similar performance to the partially 3D-printed patch antenna with a single side copper foil as the reference ground plane.

NinjaFlex and Electrifi are two popular 3D-printing filaments with unique material properties. Electrifi is a conductive filament which is useful for 3D printing digital electronic interconnects as well as antenna structures. Meanwhile, NinjaFlex is a flexible filament which, when used as an antenna substrate, supports the fabrication of conformal antennas. Previously, Electrifi or thin copper foil structures have been laminated (attached) to NinjaFlex substrates using adhesives. This paper presents a multi-material technique for directly 3D-printing Electrifi and NinjaFlex together, in a single print job, on a single-extruder printer. The antenna and substrate layers are thermally bonded to one another, during the printing process, with no adhesives added.

The technology of additive manufacturing results in 3D printing of conductive traces in radio frequency circuits. This creates a plethora of possibilities in realizing flexible and wearable electronics. While the prototypes of microstrip transmission lines and antennas have been recently reported, there is now a need of Electromagnetic Compatibility based study of such 3D printed conductive traces. This paper presents a comparative study on the near end and far end unintentional crosstalk components between a pair of microstrip transmission lines made of Copper in the presence of a 3D printed conductive trace made of a commercially available conductive filament, Electrifi. Any physical contact with the 3D printed trace has been purposefully averted to discard the high contact resistance between the trace and such contacts.

In this study, we present various examples of how thin film preparation for quartz crystal microbalance experiments informs the appropriate modeling of the data and determines which properties of the film can be quantified. The quartz crystal microbalance offers a uniquely sensitive platform for measuring fine changes in mass and/or mechanical properties of an applied film by observing the changes in mechanical resonance of a quartz crystal oscillating at high frequency. The advantages of this approach include its experimental versatility, ability to study changes in properties over a wide range of experimental time lengths, and the use of small sample sizes. We demonstrate that, based on the thickness and shear modulus of the layer deposited on the sensor, we can acquire different information from the material. Here, this concept is specifically exploited to display experimental parameters resulting in mass and viscoelastic calculations of adsorbed collagen on gold and polyelectrolyte complexes during swelling as a function of salt concentration.

In the inertial limit, the resonance frequency of the quartz crystal microbalance (QCM) is related to the coupled mass on the quartz sensor through the Sauerbrey expression that relates the mass to the change in resonance frequency. However, when the thickness of the film is sufficiently large, the relationship becomes more complicated and both the frequency and damping of the crystal resonance must be considered. In this regime, a rheological model of the material must be used to accurately extract the adhered film's thickness, shear modulus, and viscoelastic phase angle from the data. In the present work we examine the suitability of two viscoelastic models, a simple Voigt model ( Physica Scripta 1999, 59, 391-396) and a more realistic power-law model ( Langmuir 2015, 31, 4008-4017), to extract the rheological properties of a thermoresponsive hydrogel film. By changing temperature and initial dry film thickness of the gel, the operation of QCM was traversed from the Sauerbrey limit, where viscous losses do not impact the frequency, through the regime where the QCM response is sensitive to viscoelastic properties. The density-shear modulus and the viscoelastic phase angle from the two models are in good agreement when the shear wavelength ratio, d/λ

Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low-viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials, their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture, it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) with methyl, ethyl, and propyl substituents—thereby increasing the hydrophobicity with increasing side chain length—and complexing them with a common anionic polyelectrolyte, poly(styrenesulfonate). The mechanical behavior of these complexes is compared to the more hydrophilic system of poly(styrenesulfonate...

Polyelectrolyte complex (PEC) films made from oppositely charged polymer chains have applications as drug-delivery vehicles, separation membranes, and biocompatible coatings. Conventional layer-by-layer techniques for polyelectrolyte coatings are low-throughput and multistep processes that are quite slow for building films on the order of micrometers. In this work, PEC films are electrochemically deposited using a rapid one-pot method, yielding thick (1 μm) films within short experimental time scales (5 min). This rapid electrodeposition is achieved by exploiting the reduction of hydrogen peroxide at mild electrode potentials that avoid water electrolysis yet trigger the pH-responsive self-assembly of a PEC film composed of poly(acrylic) acid and poly(allylamine) HCl. In situ rheology using an electrochemical quartz crystal microbalance quantified the shear modulus–density product of the deposited layer to be on the order of 107 Pa g/cm3 at a frequency of 15 MHz, with a viscoelastic phase angle of approxi...

The additive manufacturing (AM) process is gaining massive popularity among engineers and researchers. Due to the ever increasing demands of communication speed and bandwidth for catering versatile applications, radio frequency circuits are becoming more complex leading to higher manufacturing costs. One technique to address such challenges to use AM technology for fabricating next generation radio frequency circuits with very high precision. However, materials with far lower melting points than conventional metals are a necessity for currently available AM techniques. This paper investigates the possibilty of incorporating an improved version of an industrially available conductive material to design high frequency circuits for applications from 100 MHz up to 5 GHz. Measurement data and verification result using full-wave simulation is presented.

High-flux filtration membranes constructed through scalable and sustainable methods are desirable for energy-efficient separations. Often, these criteria are difficult to be reconciled with one another. Polymeric membranes can provide high flux but frequently involve organic solvents in processing steps. Solubility of many polymeric membranes in organic media also restricts their implementation in solvent filtration. In the present work, we report a simple and high-throughput aqueous processing approach for polyelectrolyte complex (PEC) membranes with controllable porosity and stability in various aqueous and organic environments. PECs are materials composed of oppositely charged polymer chains that can form solids in aqueous environments, yet which can be dissolved in very specific salt solutions capable of breaking the interpolymer ion pairs. By exploiting the salt-induced dissolution and subsequent reformation of the complex, nano- to microporous films are rapidly synthesized which resemble membranes obtained through conventional solvent-phase inversion techniques. PECs remain stable in organic solvents because of the low dielectric constant of the environment, which enhances electrostatic interactions, making them suitable for a wide range of water and solvent filtration applications. Here, we elucidate how the polymer-phase behavior can be manipulated to exercise morphological control, test membrane performance for water and solvent filtration, and quantify the mechanical stability of PECs in relevant conditions.

As the usage of wireless technology grows, it demands more complex architectures and conformal geometries, making the manufacturing of radio frequency (RF) systems challenging and expensive. The incorporation of emerging alternative manufacturing technologies, like additive manufacturing (AM), could consequently be a unique and cost-effective solution for flexible RF and microwave circuits and devices. This work presents manufacturing methodologies of 3D-printed conformal microstrip antennas made of a commercially available conductive filament, Electrifi, as the conductive trace on a commercially available nonconductive filament, NinjaFlex, as the substrate using the fused filament fabrication (FFF) method of AM technology. Additionally, a complete high frequency characterization of the prototyped antenna was studied and presented here through a comparative analysis between full-wave simulation and measurements in a fully calibrated anechoic chamber. The prototyped antenna measures 65.55 × 55.55 × 1.2 mm3 in size and the measured results show that the 3D-printed Electrifi based patch antenna achieved very good impedance matching at a resonant frequency of 2.4 GHz and a maximum antenna gain of −2.78 dBi. Finally, conformality performances of the developed antenna were demonstrated by placing the antenna prototype on five different cylindrical curved surfaces for possible implementation in flexible electronics, smart communications, and radar applications.

The electrochemical quartz crystal microbalance (QCM) was used to investigate the deposition of poly(allylamine hydrochloride) (PAH) with molybdate anions under anodic conditions. The PAH-molybdate complex was used as a model system to understand possible deposition criteria which may be relevant to the formation of proteinaceous films on CoCrMo hip implants. Data indicate that PAH deposition will occur above ∼0.60 V vs SCE if molybdate anions are present in the electrolyte above a critical concentration, and if the polymer concentration remains below a critical value. Numerical modeling and dynamic light scattering (DLS) studies were performed to understand the conditions that enable deposition to occur at these potentials. The results indicate that PAH-molybdate complexes form most efficiently when the polyvalent positive charge and polyvalent negative charge in the system are in an optimum range with respect to each other.

Calcium phosphate (CaP) ceramics are used in orthopedics and dentistry due to their excellent biocompatibility and osseointegration. Here, the electro-assisted deposition of CaP on two different self-assembled monolayers (SAMs), 2-mercaptoacetic acid (MAA) and 2-mercaptoethanol (ME), was studied both at short (up to 3 min) and long (2 hours) deposition periods on well-defined evaporated gold surfaces. It was found that the end group of the monolayer has a major effect on the growth of the CaP coating. The deposition was slower and less electrically efficient on MAA SAM, but surface cracking was essentially eliminated due to reduction of the crystallographic mismatch. The carboxylic acid may facilitate CaP growth by attracting Ca2+ ions to the surface, which could explain the higher amount of side reactions occurring at the beginning of the deposition.

The compressive mechanical characterization of highly porous ceramics is problematic due to sensitivity to stress concentrations and localized fractures. In this paper a review of the methods used by the scientific community is done and their typical results, advantages, and shortcomings are discussed. Here, a new methodology that can address some of the problems associated with the current measurement procedures is presented. The proposed method is applied to highly porous barium titanate foams. This procedure produces more consistent data that can be analyzed and interpreted objectively. We show that properties such as the crushing or collapse stress as well as the compressive modulus cannot be extracted correctly by the conventional methods. By contrast, the proposed method collects data that is more accurate, consistent with what is expected of porous ceramics and that yields smaller measurement to measurement variation.

In this paper a Brain Computer Interface (BCI) system has been proposed to help patients suffering from motor disease, paralysis or locked in syndrome to communicate via eye blinking. In this proposed BCI system EEG data is fetched by NeuroSky Headset and then analyzed by the help of WPF (Windows Presentation Foundation) based serial monitor to detect the EEG signal when the eye gives a blink. This detection of eye blinking can be used to select predefined texts and those texts can be converted to speech. The experimental result shows that this system can be used as an effective and efficient tool to communicate through brain.