Recent research reports have underlined reverse osmosis (RO) as the most optimized technology for water desalination related applications. However, implementing this technology to seawater ...desalination is facing challenges of membrane fouling. This includes membrane biofouling, organic and inorganic fouling which adversely affect the process performance and overall treatment cost. To overcome these issues, pretreatment units ahead of the RO system are necessary to reduce RO membrane fouling and enhance its operational efficiency. This article aimed at reviewing the literature and summarizing relevant methods, mechanisms and novel developments which improve the performance of the RO systems when coupled with either conventional or non-conventional pretreatment units. Several studies suggested that the non-conventional pretreatment units were more efficient than the conventional systems for producing better water quality and minimizing the overall treatment cost. Ultrafiltration appeared to be a cost effective and efficient method of removing suspended solids (SS) and bacteria. The advent of nanostructured membranes nanofiltration has the potential of becoming preferred non-conventional desalination pretreatment over a wide range of salinity, total dissolved solids (TDS), inorganics, viruses, etc.
•Reverse osmosis (RO) water desalination has been getting very popular worldwide.•Conventional pretreatment operational cost is lower than non-conventional systems.•Non-conventional (membrane) pretreatment systems produce better water quality.•Membrane pretreatment capital cost increased by 20–40% upon feed water quality.•NF is a better pretreatment method when compared to conventional and UF.
This work reported the preparation of Mg-MOF, Fe-MOF and Fe-Mg MOF by a solvothermal technique and their characterization with FT-IR, XRD, SEM, EDS, TEM and
S
BET
analyses. The nanoparticle diameter ...ranged from 3.1 to 10.9 nm. The acidity of the MOFs was measured by nonaqueous potentiometric titration of
n
-butylamine. It was observed that the formation of a bimetallic MOF sharply increases the surface acidity and the catalytic activity. The catalytic results of the Fe-Mg MOF catalyzing the synthesis of 14-aryl-14-
H
-dibenzo
a
,
j
xanthenes in comparison with those of parent MOFs showed a higher yield of the desired product in a lower time and among various Fe : Mg, the (0.6 : 1) Fe-Mg MOF showed the highest catalytic activity and acidity. Even after the 4
th
run, the Fe-Mg MOF catalyst still maintained nearly the initial catalytic activity. The adsorption performance of Mg-MOF, Fe-MOF and Fe-Mg MOF was evaluated by batch experiments. The effect of contact time, the solution pH, the adsorbent dose and the initial concentration of the heavy metal ions was discussed. It was found that the capacity of the bimetallic Fe-Mg MOF for Pb(
ii
), Cu(
ii
) and Cd(
ii
) adsorption was higher than that of the Mg-MOF and Fe-MOF, the kinetic data followed the pseudo-second-order kinetic model and the isothermal data obeyed the Langmuir isotherm model. The mechanism of the removal of the heavy metal ions was discussed.
This work reported the preparation of Mg-MOF, Fe-MOF and Fe-Mg MOF by a solvothermal technique and their characterization with FT-IR, XRD, SEM, EDS, TEM and
S
BET
analyses.
Monometallic and bimetallic MOF/MCM-41 composites (Cu, Ag and Cu-Ag) were synthesized
via
a solvothermal method. The synthesized composites were characterized by XRD, FTIR, SEM, EDX and BET surface ...area measurements. The acidity was determined through two techniques; potentiometric titration with
n
-butyl amine for determining the strength and the total number of acid sites and FTIR spectra of chemisorbed pyridine on the surface of MOFs for determining the type of acid sites (Brønsted and/or Lewis). All the prepared MOFs showed Lewis-acid sites and the higher acidity was observed for the bimetallic Cu-Ag MOF/MCM-41 composite. The catalytic activity was examined on the synthesis of 1-amidoalkyl-2-naphthol
via
the reaction of benzaldehyde, 2-naphthol and benzamide. The best yield (92.86%) was obtained in the least time (10 min) with a molar ratio 1.2 : 1.2 : 1.7 of benzaldehyde : β-naphthol : benzamide and 0.1 g bimetallic Cu-Ag MOF/MCM-41 composite under solvent-free conditions at 130 °C. Reuse of the catalysts showed that they could be used at least four times without any reduction in the catalytic activity.
Monometallic and bimetallic MOF/MCM-41 composites (Cu, Ag and Cu-Ag) were synthesized
via
a solvothermal method.
Hydrocephalus is the most common brain disorder in children and is more common in low- and middle-income countries. Research output on hydrocephalus remains sparse and of lower quality in low- and ...middle-income countries compared with high-income countries. Most studies addressing hydrocephalus epidemiology are retrospective registry studies entailing their inherent limitations and biases. This study aimed to investigate child-related, parental, and socioeconomic risk factors of congenital hydrocephalus (CH) in a lower-middle-income country.
An investigator-administered questionnaire was used to query parents of patients with CH and controls who visited the authors' institution from 2017 until 2021. Patients with secondary hydrocephalus and children older than 2 years of age at diagnosis were excluded. Uni- and multivariable logistic regression was performed to identify the factors affecting CH development.
Seven hundred forty-one respondents (312 cases and 429 controls) were included in this study. The authors showed that maternal diseases during pregnancy (OR 3.12, 95% CI 1.96-5.03), a lack of periconceptional folic acid intake (OR 1.92, 95% CI 1.32-2.81), being a housewife (OR 2.66, 95% CI 1.51-4.87), paternal illiteracy (OR 1.65, 95% CI 1.02-2.69), parental consanguinity (OR 3.67, 95% CI 2.40-5.69), a history of other CNS conditions in the family (OR 2.93, 95% CI 1.24-7.34), conceiving a child via assisted fertilization techniques (OR 3.93, 95% CI 1.57-10.52), and the presence of other congenital anomalies (OR 2.57, 95% CI 1.38-4.87) were associated with an independent higher odds of a child having CH. Conversely, maternal hypertension (OR 0.22, 95% CI 0.09-0.48), older maternal age at delivery (OR 0.93, 95% CI 0.89-0.97), and having more abortions (OR 0.80, 95% CI 0.67-0.95) were negatively correlated with CH.
Multiple parental, socioeconomic, and child-related factors were associated with higher odds for developing CH. These results can be utilized to guide parental counseling and management, and direct social education and prevention programs.
Although titanium (Ti) alloys possess unique properties that allow them to compete with many other materials in advanced industries such as aerospace, marine and biomedical, they have poor machining ...performances. The primary objective of this study is to investigate the distribution of magnetic field intensity at the cutting environment in single-point diamond turning (SPDT) of Ti–6Al–4 V alloy and its influence on the machining performances, with the goal of achieving the desired machining conditions of magnetic field assisted ultra-precision machining, especially magnetic field intensity and the corresponding machining parameters, and to enhance the machinability of Ti–6Al–4 V alloy. In this study, magnetic field-assisted machining (MFAM) system was designed and coupled with ultra-precision machining (UPM) using single-point diamond turning for increasing the machinability and improving the surface quality of Ti6Al4V alloy machined parts. The finite element method (FEM) was developed to demonstrate the influences of the generated magnetic field on the machining processes. The Experimental results showed the capability of magnetic field assistance to enhance the machining performance of Ti–6Al–4 V alloy. These findings provided strong evidence that a magnetic field has the ability to extend cutting tool life, additionally, MFAM achieved the lowest value of surface roughness, representing a 33 percent improvement in surface roughness. This research contributes to the support of the optimum MFAM by FEM and the achievement of high-quality machined Ti alloys in UPM for similar research works, as demonstrated by the experimental results.
•The new algorithm is evaluated on Flavia dataset and on self-collected dataset of 625 leaf images.•A thorough review of different plant identification techniques is presented.•Different Classifier ...are compared for classification task.•Results show that the proposed algorithm can attain plant recognition accuracy of up to 98.75% with Flavia and 97.25% on self-collected dataset.
A large number of studies have been performed during the past few years to automatically identify the plant type in a given image. Besides common object recognition difficulties arising mainly due to light, pose and orientation variations, the plant type identification problem is further complicated by the differences in leaf shape overage and changing leaf color under different weather conditions. The limited accuracy of existing approaches can be improved using an appropriate selection of representative leaf based features. This study evaluates different handcrafted visual leaf features, their extraction techniques, and classification methods. Towards this end, a new five-step algorithm is presented (comprising image pre-processing, segmentation, feature extraction, dimensionality reduction, and classification steps) for recognition of plant type through leaf images. The proposed algorithm is evaluated on a publicly available standard dataset ‘Flavia’ of 1600 leaf images and on a self-collected dataset of 625 leaf images. With the proposed algorithm, different classifiers such as k-nearest neighbor (KNN), decision tree, naïve Bayes, and multi-support vector machines (SVM) are tested. The best performing KNN, claimed for the final results, reveals that the proposed algorithm gives precision and recall values of 97.6% and 98.8% respectively when tested on ‘Flavia’ dataset. The proposed technique is also tested on our self-collected dataset, giving respectively 96.1% and 97.3% precision and recall measure results. Results confirm that our approach, when augmented with efficient segmentation techniques on raw leaf images, can be a significantly accurate plant type recognition method in practical situations. AlexNet, a Convolutional Neural Network (CNN) based approach is also compared for classification on the datasets as oppose to handcrafted feature-based approach and it is found that the later outperforms the former in robustness when the training dataset is small.
In the present study, a bimetallic Cr-Mg-MOF was successfully synthesized by the solvothermal method and then modified by loading different amounts of phosphomolybdic acid (PMA) using a simple wet ...impregnation technique. The morphological and structural properties of the prepared samples were investigated using X-ray diffraction, TEM, SEM, BET and FTIR spectroscopy. Importantly, Mg doping not only caused the Cr-Mg-MOF to have a higher surface area than MIL-101 (Cr) or MOF-74 (Mg), but the strategy of doping metal ions can be an effective way to improve the adsorption performance of MOFs. The surface acidity and the acid strength of the samples were determined using potentiometric titration and the FTIR of pyridine adsorption. The incorporation of PMA crystals gradually enhances both the surface acidity and the acid strength of the PMA/Cr-Mg-MOF catalysts up to 75 wt%. The catalytic performances of the prepared catalysts were tested in two acid-catalyzed organic transformations, namely, 7-hydroxy-4-methyl coumarin and 3,4-dihydropyrimidinone. In the two reactions, the catalytic activity attains the maximum value at 75 wt% PMA loading. The PMA catalysts supported on Cr-Mg-MOF are potentially promising heterogeneous catalysts for acid-catalyzed organic transformations in environmentally friendly processes, to replace the use of conventional homogeneous PMA catalysts.
PMA supported on Cr-Mg-MOF has been successfully synthesized. All catalysts exhibits distinct catalytic activity in the synthesis of 3,4-dihydropyrimidinones and 7-hydroxy-4-methyl coumarin and showed excellent % yield and recycling efficiency.
Ventriculoperitoneal (VP) shunting is the most commonly performed procedure in the treatment of hydrocephalus. VP shunt migration can occur at different sites. The aim of the study was to present ...different sites of abnormal distal shunt location, pathophysiology, and the management in each situation.
Between 2014 and 2017, all patients with hydrocephalus in the Department of Neurosurgery, Cairo University, were gathered prospectively. All pediatric patients below the age of 12 years with shunt migration of the distal end of the VP shunt were identified.
Of 1092 patients operated on by the VP shunt between 2014 and 2017, 15 presented with shunt dysfunction because of distal shunt migration (6 anal, 3 scrotal, 1 colon, 1 peroral, 1 upper lumbar extrusion, 1 paraspinal, 1 penile, and 1 umbilical). Especially upper lumbar extrusion and paraspinal shunt location are extremely rare. All the 15 patients were treated successfully with VP shunts and prospectively followed until they presented with complications on different occasions.
Peritoneal complications are among the most common causes of VP failure. We present a rare complication where the shunt migrates outside the peritoneal cavity elsewhere with ambiguous pathogenesis. Special considerations have to be appointed during the shunt revision surgeries of these cases.
•The aim of the study was to present different sites of abnormal distal shunt migration and the management in each situation.•Shunt migration occurred in 1.4% in the present series of 1092 prospectively collected pediatric patients with hydrocephalus.•Six anal, 3 scrotal, 1 colon, 1 peroral, 1 upper lumbar extrusion, 1 paraspinal, 1 penile, 1 umbilical.•Especially upper lumbar extrusion and paraspinal shunt migration are extremely rare.•We recommend distal end insertion of the VP shunt using a minilaparotomy or laparoscopic surgery.
Narrowband Internet of Things (NB-IoT) provides energy-efficient communications with extended coverage for the low data rate IoT devices. In this paper, we propose a power-domain non-orthogonal ...multiple access (NOMA) scheme for the NB-IoT systems to enhance the connection density by allowing multiple IoT devices to simultaneously access one subcarrier. We consider both single-tone and multi-tone transmission modes of the NB-IoT systems, where each device can access a single subcarrier or a bond of contiguous subcarriers, respectively. We formulate joint subcarrier and power allocation problems for both transmission modes to maximize the connection density while taking the quality of service requirements and the transmit power constraints of IoT devices into account. We solve the single-tone nonconvex mixed integer programming problem by transforming it into a mixed integer linear programming problem to obtain the optimal solution. The multi-tone problem is solved by using the difference of convex programming approach to obtain a close-to-optimal solution. We also propose low-complexity heuristic algorithms to solve both problems in a suboptimal manner. The simulations results show that our proposed scheme increases the connection density of NB-IoT systems by 87% in the single-tone mode and by 24% in the multi-tone mode compared to orthogonal multiple access.
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