Josephson current-assisted reversal of a single-domain nanoscale ferromagnet driven by cosine chirp pulse.

We study the microwave-induced magnetization reversal in two systems, the microwave-driven nanomagnet (NM) and the NM coupled to a Josephson junction (JJ) under the microwave field (NM-JJ-MW). The frequency of the applied cosine chirp pulse changes nonlinearly with time to match the magnetization precession frequency. The coupling between the NM and JJ reduces the magnetization switching time as well as the optimal amplitude of the microwave field as a result of manipulating the magnetization via Josephson-to-magnetic energy ratioG. The reversal effect in NM-JJ-MW is sufficiently robust against changes in pulse amplitude and duration. In this system, the increase ofGdecreases the possibility of the non-reversing magnetic response as the Gilbert damping increases without further increase in the external microwave field. We also discuss the magnetic response of the NM driven by the ac field of two JJs in which the time-dependent frequency is controlled by the voltage across the junctions. Our results provide a controllable scheme of magnetization reversal that might help to realize fast memory devices.

Bifurcation structure and chaos in dynamics of nanomagnet coupled to Josephson junction.

Irregular easy axis reorientation features are observed in numerical simulations of the nanomagnet coupled to the Josephson junction. We study magnetization bifurcations and chaos that appear in this system due to the interplay of superconductivity and magnetism. The bifurcation structure of magnetization under the variation of Josephson to magnetic energy ratio as a control parameter demonstrates several precessional motions that are related to chaotic behavior and orbits with different periodicities in the ferromagnetic resonance region. The effect of an external periodic signal on the bifurcation structure is also investigated. The results demonstrate high-frequency modes of a periodic motion and a chaotic response near resonance. Far from the ferromagnetic resonance, we observe a quasiperiodic behavior. The obtained results explain the irregular reorientation of the easy axis and the transitions between different types of motion.

Genotypic detection of metronidazole and clarithromycin resistance in dyspeptic patients with helicobacter pylori.

In Egypt, antibiotic sensitivity analysis for Helicobacter pylori is not routinely performed. We aimed to identify the clarithromycin and metronidazole resistance directly from gastric biopsies for better guide treatment regimens. This cross-sectional descriptive study included 75 adult dyspeptic patients referred to the upper endoscopy unit in Suez Canal University Hospital, Ismailia, Egypt. Gastric biopsies were taken for rapid urease test (RUT) and cultured on brucella agar with antibiotic supplements. Genomic DNA was extracted directly from the specimen, and PCR was performed for direct detection of H. pylori. Also, to explore clarithromycin and metronidazole resistance, mutations in the 23S rRNA gene and the rdxA gene were investigated. We found that 60 samples were positive to RUT (80%), and only 4 samples were positive by culture. UreC gene was detected in 45 specimens. Meanwhile, 26 isolates were contained mutations at positions 2142 and 2143. Amplification of the metronidazole rdx gene was performed by conventional PCR. Out of 45 isolates, DNA sequence analysis of PCR product showed the wild type (ACA) in 9 isolates, while the mutant type (ATA) was detected in 28 isolates. We found a significant proportion of clarithromycin and metronidazole resistance among H. pylori infected patients in our region.

Retrograde intrarenal surgery versus percutaneous nephrolithotomy for treatment of renal pelvic stone more than 2 centimeters: a prospective randomized controlled trial.

This study aimed at investigating the efficacy and safety of retrograde intrarenal surgery (RIRS) in treatment of renal pelvic stone larger than 2 cm against the percutaneous nephrolithotomy (PCNL). Between March 2018 and December 2020, 121 patients were randomized to undergo PCNL (60 patients), or RIRS (61 patients). Both groups were compared in terms of operative time, intraoperative complications. Postoperative complications were assessed based on Clavien-Dindo grading system. Stone-free rates were evaluated by CT scan 6 weeks after surgery. No significant difference were observed between both groups in perioperative criteria. The main operative time was slightly longer in PCNL group (105 vs 95 min, p = 0.49). Stone clearance was higher in PCNL, yet the difference was not significant. (53 patients in PCNL group had either complete clearance or residual fragments < 4 mm, compared to 49 in RIRS group (p = 0.22). Blood transfusion rate was 8.3% in PCNL compared to 1.6% in RIRS group, with a trend towards significance (p = 0.08). Post-operative fever was higher in RIRS, yet it fell just short of statistical significance (13.1% vs 5.0%, p = 0.12). Compared to PCNL, RIRS displayed acceptable efficacy with less risk of bleeding requiring transfusion. It can be applied to patients with large renal pelvic stone as an alternative to PCNL.

Genotyping of Helicobacter pylori Virulence Genes cagA and vacA: Regional and National Study.

Helicobacter pylori (H. pylori) plays a crucial role in the pathogenesis of gastritis, peptic ulcer, and gastric cancer. The presence of pathogenicity islands (PAI) genes contributes to the pathogenesis of many gastrointestinal disorders. Cytotoxin-associated gene A (cagA) and vacuolating cytotoxin gene (vacA) are the most known virulence genes in H. pylori. So, our aim was to study H. pylori virulence genes' role in gastric disorders pathogenesis. Our study included 150 adult patients who suffered dyspeptic symptoms and were referred to the GIT endoscopy unit. Gastric biopsies were attained for rapid urease test (RUT) and histopathological examination, and multiplex PCR technique for detection of virulence genes was performed. It was found that 100 specimens were (RUT) positive, of which sixty samples (60%) were PCR positive for H. pylori ureC gene. The vacA and cagA genes were identified in 61.6% and 53% of H. pylori strains, respectively. Only 5 cases were vacA-positive and cagA-negative. The most virulent vacA s1 allele existed in 56.6% of cases. Out of the 60 H. pylori strains, 66% had at least one virulence gene and 34% did not show any virulence gene. H. pylori infection showed significant increase with age. H. pylori are prevalent amid dyspeptic patients in our region. The main genotype combinations were vacA+/cagA+ of s1m1 genotype and they were frequently associated with peptic ulcer diseases, gastritis, and gastroesophageal reflux disease.

The interaction of mercury and methylmercury with chalcogenide nanoparticles.

Mercury (Hg) and methylmercury (CH3Hg) bind strongly to micro and nano (NP) particles and this partitioning impacts their fate and bioaccumulation into food webs, and, as a result, potential human exposure. This partitioning has been shown to influence the bioavailability of inorganic Hg to methylating bacteria, with NP-bound Hg being more bioavailable than particulate HgS, or organic particulate-bound Hg. In this study we set out to investigate whether the potential interactions between dissolved ionic Hg (HgII) and CH3Hg and NPs was due to incorporation of Hg into the core of the cadmium selenide and sulfide (CdSe; CdS) nanoparticles (metal exchange or surface precipitation), or due purely to surface interactions. The interaction was assessed based on the quenching of the fluorescence intensity and lifetime observed during HgII or CH3Hg titration experiments of these NP solutions. Additional analysis using inductively coupled plasma mass spectrometry of CdSe NPs and the separated solution, obtained after HgII additions, showed that there was no metal exchange, and X-ray photoelectron spectroscopy confirmed this and further indicated that the Hg was bound to cysteine, the NP capping agent. Our study suggests that Hg and CH3Hg adsorbed to the surfaces of NPs would have different bioavailability for release into water or to (de)methylating organisms or for bioaccumulation, and provides insights into the behavior of Hg in the environment in the presence of natural or manufactured NPs.

The precipitation, growth and stability of mercury sulfide nanoparticles formed in the presence of marine dissolved organic matter.

The methylation of mercury is known to depend on the chemical forms of mercury (Hg) present in the environment and the methylating bacterial activity. In sulfidic sediments, under conditions of supersaturation with respect to metacinnabar, recent research has shown that mercury precipitates as ß-HgS(s) nanoparticles (ß-HgS(s)nano). Few studies have examined the precipitation of ß-HgS(s)nano in the presence of marine dissolved organic matter (DOM). In this work, we used dynamic light scattering (DLS) coupled with UV-Vis spectroscopy and transmission electron microscopy (TEM) to investigate the formation and fate of ß-HgS(s)nano formed in association with marine DOM extracted from the east and west of Long Island Sound, and at the shelf break of the North Atlantic Ocean, as well as with low molecular weight thiols. We found that while the ß-HgS(s)nano formed in the presence of oceanic DOM doubled in size after 5 weeks, those forming in solutions with coastal DOM did not grow over time. In addition, when the HgII : DOM ratio was varied, ß-HgS(s)nano only rapidly aggregated at high ratios (>41 µmol HgII per mg C) where the concentration of thiol groups was determined to be substantially low relative to HgII. This suggests that functional groups other than thiols could be involved in the stabilization of ß-HgS(s)nano. Furthermore, we showed that ß-HgS(s)nano forming under anoxic conditions remained stable and could therefore persist in the environment sufficiently to impact the methylation potential. Exposure of ß-HgS(s)nano to sunlit and oxic environments, however, caused rapid aggregation and sedimentation of the nanoparticles, suggesting that photo-induced changes or oxidation of organic matter adsorbed on the surface of ß-HgS(s)nano affected their stability in surface waters.

Mercury flux from salt marsh sediments: Insights from a comparison between 224Ra/228Th disequilibrium and core incubation methods.

In aquatic environments, sediments are the main location of mercury methylation. Thus, accurate quantification of methylmercury (MeHg) fluxes at the sediment-water interface is vital to understanding the biogeochemical cycling of mercury, especially the toxic MeHg species, and their bioaccumulation. Traditional approaches, such as core incubations, are difficult to maintain at in-situ conditions during assays, leading to over/underestimation of benthic fluxes. Alternatively, the 224Ra/228Th disequilibrium method for tracing the transfer of dissolved substances across the sediment-water interface, has proven to be a reliable approach for quantifying benthic fluxes. In this study, the 224Ra/228Th disequilibrium and core incubation methods were compared to examine the benthic fluxes of both 224Ra and MeHg in salt marsh sediments of Barn Island, Connecticut, USA from May to August, 2016. The two methods were comparable for 224Ra but contradictory for MeHg. The radiotracer approach indicated that sediments were always the dominant source of both total mercury (THg) and MeHg. The core incubation method for MeHg produced similar results in May and August, but an opposite pattern in June and July, which suggested sediments were a sink of MeHg, contrary to the evidence of significant MeHg gradients between overlying water and porewater at the sediment-water interface. The potential reasons for such differences are discussed. Overall, we conclude that the 224Ra/228Th disequilibrium approach is preferred for estimating the benthic flux of MeHg and that sediment is indeed an important MeHg source in this marshland, and likely in other shallow coastal waters.

The role of neural precursor cell-expressed developmentally down-regulated protein 9 in predicting bacillus Calmette-Guerin response in nonmuscle invasive bladder cancer.

OBJECTIVE: To report the sensitivity and specificity of neural precursor cell-expressed developmentally down-regulated protein 9 (NEDD9) protein high expression in predicting BCG response and its effect on recurrence or progression free survivals. PATIENTS AND METHODS: Between May 2014 and April 2017, a prospective cohort study was conducted on 105 patients with intermediate or high-risk nonmuscle invasive bladder cancer. Immunohistochemical staining with mouse monoclonal anti-NEDD9 antibody was done. Examination of the slides was done to detect NEDD9 cytoplasmic expression. Intravesical induction bacillus Calmette-Guerin (BCG) instillation therapy was started for all patients 2 to 4 weeks after endoscopy with once weekly instillation for 6 weeks. Intravesical maintenance BCG instillation was then continued every 3 months for at least 1 year. Follow up with cystoscopy every 3 months for 2 years and every 6 months after that. RESULTS: The mean age ± SD of the patients was 57 ± 4.5 years. The median follow-up period was 25 (12-36) months. NEDD9 protein was highly expressed in 61 (58.1%) patients, whereas low expression was in 44 (41.9%) patients. Sensitivity and specificity of NEDD9 high expression in predicting recurrence were 83.6% and 64.2%, respectively. Its sensitivity and specificity in predicting progression to muscle invasion or distant metastases were 91.3% and 51.2%, respectively. Its sensitivity and specificity in predicting complete response to BCG therapy were 84.1% and 80.9%. Kaplan-Meier test showed highly significant difference (P<0.0001) in survival without recurrence or progression between patients showing high expression and those showing low expression. CONCLUSION: NEDD9 protein tissue marker could be used as a predictive marker for BCG response in nonmuscle invasive bladder cancer with reasonable sensitivity and specificity.

Dimethylmercury Formation Mediated by Inorganic and Organic Reduced Sulfur Surfaces.

Underlying formation pathways of dimethylmercury ((CH3)2Hg) in the ocean are unknown. Early work proposed reactions of inorganic Hg (Hg(II)) with methyl cobalamin or of dissolved monomethylmercury (CH3Hg) with hydrogen sulfide as possible bacterial mediated or abiotic pathways. A significant fraction (up to 90%) of CH3Hg in natural waters is however adsorbed to reduced sulfur groups on mineral or organic surfaces. We show that binding of CH3Hg to such reactive sites facilitates the formation of (CH3)2Hg by degradation of the adsorbed CH3Hg. We demonstrate that the reaction can be mediated by different sulfide minerals, as well as by dithiols suggesting that e.g. reduced sulfur groups on mineral particles or on protein surfaces could mediate the reaction. The observed fraction of CH3Hg methylated on sulfide mineral surfaces exceeded previously observed methylation rates of CH3Hg to (CH3)2Hg in seawaters and we suggest the pathway demonstrated here could account for much of the (CH3)2Hg found in the ocean.

Enhanced availability of mercury bound to dissolved organic matter for methylation in marine sediments.

The forms of inorganic mercury (HgII) taken up and methylated by bacteria in sediments still remain largely unknown. From pure cultures studies, it has been suggested that dissolved organic matter (DOM) may facilitate the uptake either by acting as a shuttle molecule, transporting the HgII atom to divalent metal transporters, or by binding HgII and then being transported into the cell as a carbon source. Enhanced availability of Hg complexed to DOM has however not yet been demonstrated in natural systems. Here, we show that HgII complexed with DOM of marine origin was up to 2.7 times more available for methylation in sediments than HgII added as a dissolved inorganic complex (HgII(aq)). We argue that the DOM used to complex HgII directly facilitated the bacterial uptake of HgII whereas the inorganic dissolved HgII-complex adsorbed to the sediment matrix before forming bioavailable dissolved HgII complexes. We further demonstrate that differences in net methylation in sediments with high and low organic carbon content may be explained by differences in the availability of carbon to stimulate the activity of Hg methylating bacteria rather than, as previously proposed, be due to differences in HgII binding capacities between sediments.