Phase change material-based nano-cavity as an efficient optical modulator.

Structural phase transition induced by temperature or voltage in phase change materials has been used for many tunable photonic applications. Exploiting reversible and sub-ns fast switching in antimony trisulfide (Sb2S3) from amorphous (Amp) to crystalline (Cry), we introduced a reflection modulator based on metal-dielectric-metal structure. The proposed design exhibits tunable, perfect, and multi-band absorption from visible to the near-infrared region. The reflection response of the system shows >99% absorption of light at normal incidence. The maximum achievable modulation efficiency with a narrow line width is ∼98%. Interestingly, the designed cavity supports critical resonance in an ultrathin (∼λ/15) Sb2S3 film with perfect, broadband, and tunable absorption. Finally, we proposed a novel hybrid cavity design formed of Cry and Amp Sb2S3 thin films side-by-side to realize an optical modulator via relative motion between the incident light beam and cavity. The proposed lithographic free structure can be also used for filtering, optical switching, ultrathin photo-detection, solar energy harvesting, and other energy applications.

Significantly enhanced electrocatalytic activity of copper for hydrogen evolution reaction through femtosecond laser blackening.

In this work, we report on the creation of a black copper via femtosecond laser processing and its application as a novel electrode material. We show that the black copper exhibits an excellent electrocatalytic activity for hydrogen evolution reaction (HER) in alkaline solution. The laser processing results in a unique microstructure: microparticles covered by finer nanoparticles on top. Electrochemical measurements demonstrate that the kinetics of the HER is significantly accelerated after bare copper is treated and turned black. At -0.325 V (v.s. RHE) in 1 M KOH aqueous solution, the calculated area-specific charge transfer resistance of the electrode decreases sharply from 159 Ω cm2 for the untreated copper to 1 Ω cm2 for the black copper. The electrochemical surface area of the black copper is measured to be only 2.4 times that of the untreated copper and therefore, the significantly enhanced electrocatalytic activity of the black copper for HER is mostly a result of its unique microstructure that favors the formation and enrichment of protons on the surface of copper. This work provides a new strategy for developing high-efficient electrodes for hydrogen generation.

Peripheral Merozoite Surface Proteins Are Targets of Naturally Acquired Immunity against Malaria in both India and Ghana.

Development of a successful blood-stage vaccine against Plasmodium falciparum malaria remains a high priority. Immune-epidemiological studies are effective tools for the identification of antigenic targets of naturally acquired immunity (NAI) against malaria. However, differences in study design and methodology may compromise interstudy comparisons. Here, we assessed antibody responses against intact merozoites and a panel of 24 recombinant merozoite antigens in longitudinal cohort studies of Ghanaian (n = 115) and Indian (n = 121) populations using the same reagents and statistical methods. Anti-merozoite antibodies were associated with NAI in both the Indian (hazard ratio [HR] = 0.41, P = 0.020) and the Ghanaian (HR = 0.17, P < 0.001) participants. Of the 24 antigen-specific antibodies quantified, 12 and 8 were found to be protective in India and Ghana, respectively. Using least absolute shrinkage and selection operator (LASSO) regression, a powerful variable subselection technique, we identified subsets of four (MSP6, MSP3.7, MSPDBL2, and Pf12) and five (cMSP33D7, MSP3.3, MSPDBL1, GLURP-R2, and RALP-1) antigens that explained NAI better than the individual antibodies in India (HR = 0.18, P < 0.001) and Ghana (HR = 0.31, P < 0.001), respectively. IgG1 and/or IgG3 subclasses against five antigens from these subsets were associated with protection. Through this comparative study, maintaining uniformity of reagents and methodology, we demonstrate that NAI across diverse geographic regions may result from antibodies to multiple antigenic targets that constitute the peripheral merozoite surface protein complexes.

Boosting Perovskite Photodetector Performance in NIR Using Plasmonic Bowtie Nanoantenna Arrays.

Triple-cation mixed metal halide perovskites are important optoelectronic materials due to their high photon to electron conversion efficiency, low exciton binding energy, and good thermal stability. However, the perovskites have low photon to electron conversion efficiency in near-infrared (NIR) due to their weak intrinsic absorption at longer wavelength, especially near the band edge and over the bandgap wavelength. A plasmonic functionalized perovskite photodetector (PD) is designed and fabricated in this study, in which the perovskite ((Cs0.06 FA0.79 MA0.15 )Pb(I0.85 Br0.15 )3 ) active materials are spin-coated on the surface of Au bowtie nanoantenna (BNA) arrays substrate. Under 785 nm laser illumination, near the bandedge of perovskite, the fabricated BNA-based plasmonic PD exhibits ≈2962% enhancement in the photoresponse over the Si/SiO2 -based normal PD. Moreover, the detectivity of the plasmonic PD has a value of 1.5 × 1012 with external quantum efficiency as high as 188.8%, more than 30 times over the normal PD. The strong boosting in the plasmonic PD performance is attributed to the enhanced electric field around BNA arrays through the coupling of localized surface plasmon resonance. The demonstrated BNA-perovskite design can also be used to enhance performance of other optoelectronic devices, and the concept can be extended to other spectral regions with different active materials.

All-optical logic gates using dielectric-loaded waveguides with quasi-rhombus metasurfaces.

Nanostructure and nanoantenna-based all-optical (AO) devices have attracted significant research interests in recent years due to their small size, high information capacity, ultrafast processing, low power consumption, and overall practicality. Here, in this Letter, we propose a novel metasurface having quasi-rhombus-shaped antennas to modulate optical modes in a dielectric-loaded waveguide for the realization of a complete family of logic gates including NOT, AND, OR, XOR, NAND, NOR, and XNOR. These logic operations are realized using destructive and constructive interferences between the input optical signals. The high contrast ratios of about 33.39, 27.69, and 33.11 dB are achieved for the NAND, NOR, and XNOR logic gates, respectively, with the speed as high as 108 Gb/s.

Creating superhydrophobic and antibacterial surfaces on gold by femtosecond laser pulses.

Femtosecond laser-induced surface structuring is a promising technique for the large-scale formation of nano- and microscale structures that can effectively modify materials' optical, electrical, mechanical, and tribological properties. Here we perform a systematic study on femtosecond laser-induced surface structuring on gold (Au) surface and their effect on both hydrophobicity and bacterial-adhesion properties. We created various structures including subwavelength femtosecond laser-induced periodic surface structures (fs-LIPSSs), fs-LIPSSs covered with nano/microstructures, conic and 1D-rod-like structures ( ≤ 6 µm), and spherical nanostructures with a diameter ≥ 10 nm, by raster scanning the laser beam, at different laser fluences. We show that femtosecond laser processing turns originally hydrophilic Au to a superhydrophobic surface. We determine the optimal conditions for the creation of the different surface structures and explain the mechanism behind the formed structures and show that the laser fluence is the main controlling parameter. We demonstrate the ability of all the formed surface structures to reduce the adhesion of Escherichia coli (E. coli) bacteria and show that fs-LIPSSs enjoys superior antibacterial adhesion properties due to its large-scale surface coverage. Approximately 99.03% of the fs-LIPSSs surface is free from bacterial adhesion. The demonstrated physical inhibition of bacterial colonies and biofilm formation without antibiotics is a crucial step towards reducing antimicrobial-resistant infections.

Breadth of Functional Antibodies Is Associated With Plasmodium falciparum Merozoite Phagocytosis and Protection Against Febrile Malaria.

BACKGROUND: The specific targets of functional antibodies against Plasmodium falciparum merozoites remain largely unexplored and, more importantly, their relevance to naturally acquired immunity in longitudinal cohort studies (LCSs) is yet to be tested. METHODS: Functionality of immunoglobulin G (IgG) antibodies against 24 merozoite antigens was determined at the baseline of an LCS in Ghana using a bead-based opsonic phagocytosis assay (BPA). Antigen-specific IgG3 subclass antibodies were quantified in the same samples by the Luminex multiplex system. RESULTS: A wide range of BPA activity was observed across the different antigens. High BPA responses of nMSP3K1, GLURP-R2, MSP23D7, MSP119k, and PfRh2-2030 coupled beads were significantly associated with a higher probability of children not experiencing febrile malaria. Children with high breadth of functional antibodies against these antigens together with cMSP33D7 had a significantly reduced risk of febrile malaria (adjusted hazard ratio, 0.36 [95% confidence interval, .18-.72]; P = .004). Five of the 6 BPA activities significantly (likelihood ratio rest, P ≤ .05) contributed to the protective immunity observed with the IgG3 antibodies. CONCLUSIONS: The development of BPA allowed profiling of functional antibodies in an LCS. Identification of targets of opsonic phagocytosis may have implications in the development of a subunit malaria vaccine.

Quasi-rhombus metasurfaces as multimode interference couplers for controlling the propagation of modes in dielectric-loaded waveguides.

Metasurfaces can control the propagation of free space and guided modes by imparting a phase gradient and modifying the mode propagation properties. Here we propose a design to control optical signals in a dielectric-loaded waveguide using quasi-rhombus gradient plasmonic metasurface structure. The metasurface acts as a multimode interference coupler that can focus, route, and split the propagating field in UV-visible spectral range. The ability to gain full control on waveguided mode with minimal footprint can significantly impact miniaturization of optical devices and photonic integrated circuits.

How To Obtain Six Different Superwettabilities on a Same Microstructured Pattern: Relationship between Various Superwettabilities in Different Solid/Liquid/Gas Systems.

A range of different superwettabilities were obtained on femtosecond laser-structured Al surfaces. The formation mechanism of each superwetting state is discussed in this paper. It is revealed that the underwater oil droplet and bubble wettabilities of a solid surface have a close relationship with its water wettability. The laser-induced hierarchical microstructures showed superhydrophilicity in air but showed superoleophobicity/superaerophobicity after immersion in water. When such microstructures were further modified with a low-surface-energy monolayer, the wettability of the resultant surface would turn to superhydrophobicity with ultralow water adhesion in air and superoleophilicity/superaerophilicity in water. The understanding of the relationship among the above-mentioned six different superwettabilities is highly important in the design of various superwetting microstructures, transforming the structures from one superwetting state to another state and better using the artificial superwetting materials.

Femtosecond Laser-Structured Underwater "Superpolymphobic" Surfaces.

In this work, the surfaces that repel liquid polydimethylsiloxane (PDMS) droplets in water were created by femtosecond laser treatment. We define this superwetting phenomenon as underwater "superpolymphobicity". The resultant underwater superpolymphobic silicon surface shows a contact angle of 159 ± 1° and a sliding angle of 1.5 ± 0.5° to liquid PDMS droplets in water. This underwater superpolymphobicity can be achieved on a wide range of hydrophilic materials, including semiconductors, glass, and metals. The adhesion between the liquid polymer and a solid substrate is effectively prevented by the underwater superpolymphobic microstructures. The underwater superpolymphobicity will have a great significance in designing the adhesion between the polymer and a solid substrate, controlling the shape of the cured polymer materials, as well as nearly all the applications based on the polymer materials.

Bioinspired Hierarchical Surfaces Fabricated by Femtosecond Laser and Hydrothermal Method for Water Harvesting.

The world is facing a global issue of water scarcity where two-thirds of the population does not have access to safe drinking water. Water harvesting from the ambient environment has a potential equivalent to ∼10% of the fresh water available on the earth's surface, but its efficiency requires a special control of surface morphology. We report a novel facile physicochemical hybrid method that combines femtosecond laser structuring with hydrothermal treatment to create a surface with a well-arranged hierarchical nanoneedle structures. Polydimethylsiloxane treatment of the thus-produced hierarchical structures nurtured superhydrophobic functionality with a very low water sliding angle (∼3°) and a high water adhesion ability. About 2.2 times higher water-collection efficiency was achieved using hierarchical structures over untreated flat Ti surfaces of the same area under a given experimental condition. The comparison of water-collection behavior with other samples showed that the improved efficiency is due to the structure, and wettability induced superior water attraction and removal ability. Moreover, a uniform water condensation under low humidity (28%) is achieved, which has potential applications in harvesting water from arid environments and in high-precision drop control.

Cytophilic Antibodies Against Key Plasmodium falciparum Blood Stage Antigens Contribute to Protection Against Clinical Malaria in a High Transmission Region of Eastern India.

Background: The collection of clinical data from a tribal population in a malaria-endemic area of India suggests the occurrence of naturally acquired immunity (NAI) against Plasmodium falciparum malaria. Methods: Quantity and functionality of immunoglobulin G (IgG) antibodies against intact merozoites and recombinant proteins were assessed in a 13-month longitudinal cohort study of 121 individuals, 3-60 years of age. Results: Opsonic phagocytosis of merozoites activity was strongly associated (hazard ratio [HR] = 0.34; 95% confidence interval [CI] = .18-.66; P = .0013) with protection against febrile malaria. Of the different IgG subclasses, only IgG3 antibodies against intact whole merozoites was significantly associated with protection against febrile malaria (HR = 0.47; 95% CI = .26-.86; P = .01). Furthermore, a combination of IgG3 antibody responses against Pf12, MSP3.7, MSP3.3, and MSP2FC27 was strongly associated with protection against febrile malaria (HR = 0.15; 95% CI, .06-.37; P = .0001). Conclusions: These data suggest that NAI may, at least in part, be explained by opsonic phagocytosis of merozoites and IgG3 responses against whole merozoites, and in particular to a combination of 4 antigens is critical in this population. These results may have implications in the development of a subunit malaria vaccine. Opsonic phagocytosis of Plasmodium falciparum merozoites was associated with protection against clinical malaria in an India population. Antibody profiling identified four merozoite antigens (Pf12, MSP3.7, MSP3.3, and MSP2) as targets of protective Immunoglobuline G3 antibodies.

Lactococcus lactis provides an efficient platform for production of disulfide-rich recombinant proteins from Plasmodium falciparum.

BACKGROUND: The production of recombinant proteins with proper conformation, appropriate post-translational modifications in an easily scalable and cost-effective system is challenging. Lactococcus lactis has recently been identified as an efficient Gram positive cell factory for the production of recombinant protein. We and others have used this expression host for the production of selected malaria vaccine candidates. The safety of this production system has been confirmed in multiple clinical trials. Here we have explored L. lactis cell factories for the production of 31 representative Plasmodium falciparum antigens with varying sizes (ranging from 9 to 90 kDa) and varying degree of predicted structural complexities including eleven antigens with multiple predicted structural disulfide bonds, those which are considered difficult-to-produce proteins. RESULTS: Of the 31 recombinant constructs attempted in the L. lactis expression system, the initial expression efficiency was 55% with 17 out of 31 recombinant gene constructs producing high levels of secreted recombinant protein. The majority of the constructs which failed to produce a recombinant protein were found to consist of multiple intra-molecular disulfide-bonds. We found that these disulfide-rich constructs could be produced in high yields when genetically fused to an intrinsically disorder protein domain (GLURP-R0). By exploiting the distinct biophysical and structural properties of the intrinsically disordered protein region we developed a simple heat-based strategy for fast purification of the disulfide-rich protein domains in yields ranging from 1 to 40 mg/l. CONCLUSIONS: A novel procedure for the production and purification of disulfide-rich recombinant proteins in L. lactis is described.

Malaria epidemiology in an area of stable transmission in tribal population of Jharkhand, India.

BACKGROUND: Malaria remains an important health problem in India with approximately 1 million cases in 2014. Of these, 7% occurred in the Jharkhand state mainly in the tribal population. METHODS: This study was conducted in Dumargarhi, a tribal village about 42 km east of Ranchi city, Jharkhand, from May 2014 to September 2016. Four point prevalence surveys were carried out during consecutive high (October-December) and low (June-August) transmission seasons. Malaria cases were recorded from April 2015 to April 2016 through fortnightly visits to the village. Adult mosquito densities were monitored fortnightly by manual catching using suction tube method. RESULTS: The study area consists of five hamlets inhabited by 945 individuals living in 164 households as recorded through a house-to-house census survey performed at enrollment. The study population consisted predominantly of the Munda (n = 425, 45%) and Oraon (n = 217, 23%) ethnic groups. Study participants were categorized as per their age 0-5, 6-10, 11-15 and >15 years. There were 99 cases of clinical malaria from April 2015 to April 2016 and all malaria cases confirmed by microscopy were attributed to Plasmodium falciparum (94 cases) and Plasmodium vivax (5 cases), respectively. During the high transmission season the mean density of P. falciparum parasitaemia per age group increased to a peak level of 23,601 parasites/µl in the 6-10 years age group and gradually declined in the adult population. Malaria attack rates, parasite prevalence and density levels in the study population showed a gradual decrease with increasing age. This finding is consistent with the phenomenon of naturally acquired immunity against malaria. Three vector species were detected: Anopheles fluviatilis, Anopheles annularis, and Anopheles culicifacies. The incoherence or complete out of phase pattern of the vector density peaks together with a high prevalence of parasite positive individuals in the study population explains the year-round malaria transmission in the study region. CONCLUSIONS: The collection of clinical data from a well-characterized tribal cohort from Jharkhand, India, has provided evidence for naturally acquired immunity against malaria in this hyperendemic region. The study also suggests that enforcement of existing control programmes can reduce the malaria burden further.

A transcriptomic approach for exploring the molecular basis for dosha-balancing property-based classification of plants in Ayurveda.

In Ayurveda, a healthy body is defined by a balance among the three doshas (Vata, Pitta, Kapha) and ailments result due to imbalances among them. It prescribes specific plant parts/tissues collected in a season-specific manner for curing dosha-related imbalances but the plants prescribed for treating a particular dosha imbalance belong to taxonomically diverse families and often contain similar classes of phytomolecules, making it difficult to provide a phytochemical validation for any similarity that might exist among them. This exploratory study hypothesised that plants of the same dosha-curing group may have similarity at the transcript level. For proving/disproving the hypothesis, cDNA-AFLP and specific expression subset analysis (SESA) were carried out on the Ayurveda-defined active tissues of four representative plants each of the three dosha-balancing groups. cDNA-AFLP analyses indicated that even though the plants belonging to a particular dosha-group may widely differ at the transcript level, there is a small fraction of transcripts that is monomorphic among their active tissues. SESA (Tester-active tissue cDNA; Driver-cDNA from other major tissue[s]) generated 803 subtractive ESTs from the twelve plants that yielded 150 unigenes upon assembly (of ESTs from each plant separately). Cross-plant EST assembly for plants in the same dosha group also corroborated the results. Although a distinct pattern of transcripts was not observed across all the plants in a particular dosha group, some commonalities were obtained that need further characterization towards searching for the hitherto elusive similarity among plants of the same group.

Simple and reliable methods for the determination of three steroidal glycosides in the eight species of Solanum by reversed-phase HPLC coupled with diode array detection.

INTRODUCTION: Solanum species are important ingredients of many traditional Indian medicines and thus the quality control of their herbal formulations is of paramount concern. OBJECTIVE: To establish a simple and effective high-performance liquid chromatographic (HPLC) method to evaluate the quality of Solanum species and their herbal formulations. METHODOLOGY: A rapid, simple, sensitive, robust and reproducible HPLC method was developed for the determination of three steroidal glycosides (SG); indioside D, solamargine and α-solanine in eight species of the genus Solanum. The analytes were separated on a monolithic performance RP-18e column (100 mm × 4.6 mm i.d.) using a gradient elution of acetonitile-water containing 0.1% trifluoroacetic acid (TFA) as the mobile phase with a flow rate 0.4 mL/min and UV detection at λ 210 nm. RESULTS: The method was linear over the range 3-15 µg/mL (r > 9994). Accuracy, precision and repeatability were all within the required limits. The mean recoveries measured at the three concentrations were higher than 98.8% with RSD < 2% for the targets. CONCLUSION: The established method is simple and can be used as a tool for quality control of plant material or herbal formulation containing SG.

SARS-CoV-2 Vaccines: Types, Working Principle, and Its Impact on Thrombosis and Gastrointestinal Disorders.

In the current scenario of the coronavirus pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), considerable efforts have been made to control the pandemic by the development of a strong immune system through massive vaccination. Just after the discovery of the genetic sequences of SARS-CoV-2, the development of vaccines became the prime focus of scientists around the globe. About 200 SARS-CoV-2 candidate vaccines have already been entered into preclinical and clinical trials. Various traditional and novel approaches are being utilized as a broad range of platforms. Viral vector (replicating and non-replicating), nucleic acid (DNA and RNA), recombinant protein, virus-like particle, peptide, live attenuated virus, an inactivated virus approaches are the prominent attributes of the vaccine development. This review article includes the current knowledge about the platforms used for the development of different vaccines, their working principles, their efficacy, and the impacts of COVID-19 vaccines on thrombosis. We provide a detailed description of the vaccines that are already approved by administrative authorities. Moreover, various strategies utilized in the development of emerging vaccines that are in the trial phases along with their mode of delivery have been discussed along with their effect on thrombosis and gastrointestinal disorders.

Cloning and Recombinant Protein Expression in Lactococcus lactis.

The Lactococcus lactis, a Gram-positive bacteria, is an ideal expression host for the overproduction of heterologous proteins in a properly folded and functional form. L. lactis has been identified as an efficient cell factory, generally recognized as safe (GRAS), has a long history of safe use in food production, and is known to have probiotic properties. Key desirable features of L. lactis include the following: (1) rapid growth to high cell densities, not requiring aeration which facilitates large-scale fermentation; (2) its Gram-positive nature precludes the presence of contaminating endotoxins; (3) the capacity to secrete stable recombinant protein into the growth medium with few proteases resulting in a properly folded, full-length protein; and (4) the availability of diverse expression vectors facilitating various cloning options. We have previously described production of several recombinant proteins with varying degrees of predicted structural complexities using the L. lactis pH-dependent P170 promoter. The purpose of this chapter is to provide a detailed protocol for facilitating wider application of L. lactis as a reliable platform for expression of heterologous recombinant proteins in soluble form. Here, we present details of the various steps involved such as cloning of the target gene in appropriate expression plasmid vector, determination of the expression levels of the heterologous protein, and initial purification of the expressed soluble recombinant protein of interest.

Nature-Inspired Surface Engineering for Efficient Atmospheric Water Harvesting.

Atmospheric water harvesting is a sustainable solution to global water shortage, which requires high efficiency, high durability, low cost, and environmentally friendly water collectors. In this paper, we report a novel water collector design based on a nature-inspired hybrid superhydrophilic/superhydrophobic aluminum surface. The surface is fabricated by combining laser and chemical treatments. We achieve a 163° contrast in contact angles between the superhydrophilic pattern and the superhydrophobic background. Such a unique superhydrophilic/superhydrophobic combination presents a self-pumped mechanism, providing the hybrid collector with highly efficient water harvesting performance. Based on simulations and experimental measurements, the water harvesting rate of the repeating units of the pattern was optimized, and the corresponding hybrid collector achieves a water harvesting rate of 0.85 kg m-2 h-1. Additionally, our hybrid collector also exhibits good stability, flexibility, as well as thermal conductivity and hence shows great potential for practical application.

Human blood neutrophils generate ROS through FcγR-signaling to mediate protection against febrile P. falciparum malaria.

Blood phagocytes, such as neutrophils and monocytes, generate reactive oxygen species (ROS) as a part of host defense response against infections. We investigated the mechanism of Fcγ-Receptor (FcγR) mediated ROS production in these cells to understand how they contribute to anti-malarial immunity. Plasmodium falciparum merozoites opsonized with naturally occurring IgG triggered both intracellular and extracellular ROS generation in blood phagocytes, with neutrophils being the main contributors. Using specific inhibitors, we show that both FcγRIIIB and FcγRIIA acted synergistically to induce ROS production in neutrophils, and that NADPH oxidase 2 and the PI3K intracellular signal transduction pathway were involved in this process. High levels of neutrophil ROS were also associated with protection against febrile malaria in two geographically diverse malaria endemic regions from Ghana and India, stressing the importance of the cooperation between anti-malarial IgG and neutrophils in triggering ROS-mediated parasite killing as a mechanism for naturally acquired immunity against malaria.