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Advantages of the Surface Structuration of KBr Materials for Spectrometry and Sensors
摘要： A potassium bromide (KBr) material, which has been widely used as the key element in Fourier spectrometers and as the output window of the IR-lasers, was studied via applying carbon nanotubes in order to modify the potassium bromide surface. The laser-oriented deposition method was used to place the carbon nanotubes at the matrix material surface in the vertical position at different electric ?elds varying from 100 to 600 V × cm?1. The main idea of the improvement of the spectral properties of the potassium bromide structure is connected with the fact that the refractive index of the carbon nanotubes is substantially less than the refractive index of the studied material, and the small diameter of the carbon nanotubes allows one to embed these nano-objects in the voids of the lattice of the model matrix systems. Moreover, the mechanical characteristics and wetting features of potassium bromide structures have been investigated under the condition mentioned above. Analytical and quantum-chemical simulations have supported the experimental results.
关键词： surface structuration,potassium bromide,mechanical and wetting properties,laser-oriented deposition method,carbon nanotubes,spectra
更新于2025-09-10 09:29:36
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Stable Structural Phase of Potassium-Doped <i>p</i> -Terphenyl and Its Semiconducting State
摘要： The potassium-doped p-terphenyl compounds were synthesized in recent experiments and the superconductivity with high transition temperatures were reported, but the atomic structure of potassium-doped p-terphenyl is unclear. In this paper, we studied the structural and electronic properties of potassium-doped p-terphenyl with various doping levels by the first-principles simulation. We first find out the low energy position of K atom in intralayer interstitial space of the molecular layer, then examine whether two rows of K atoms can be accommodated in this one space, at last the effect of the interlayer arrangement between adjacent two molecular layers on total energy is taken into account. Our results show that the doped K atoms prefer to stay at the bridge site of single C-C bond connected two phenyls instead of locating at the site above the phenyl ring, distinct from the situation of K-doped picene and phenanthrene. Among the possible structural phases of Kx-p-terphenyl, the K2-p-terphenyl phase with P212121 group symmetry is determined to be most appropriate, which is different from the one in recent report. The stable K2-p-terphenyl phase is semiconducting with an energy gap of 0.3 eV and the bands from the lowest unoccupied molecular orbitals are just fully filled by the electrons transferred from K atoms.
关键词： Plasmonics,First-principles simulation,Semiconducting state,Magnetic,Potassium-doped p-terphenyl,Superconductivity,Optical,Hybrid Materials
更新于2025-09-10 09:29:36
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DIRECT SPECTROPHOTOMETRIC DETERMINATION OF ATENOLOL AND TIMOLOL ANTI-HYPERTENSIVE DRUGS
摘要： Objective: Direct and sensitive spectrophotometric method is described for the quantitative determination of some anti-hypertensive drugs such as atenolol (ATN) and timolol (TIM) in pure forms as well as in their dosage forms. Methods: The proposed method is based on the redox reaction between the selected drugs and KMnO4 in alkaline medium. The method involves treating the aqueous solution of the selected drugs with KMnO4 in alkaline medium and measuring the bluish-green product at 610 nm. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. Results: The fixed-time method is adopted for constructing the calibration curves, which were found to be linear over the concentration ranges of 2.0–14 m g/ml and 2.0–28 m g/ml for ATN and TIM, respectively. The determination of the studied drugs by initial rate, variable time and rate constant method was workable with the calibration equations obtained but the fixed time method has been found to be more applicable. Conclusion: The applicability of the proposed method was demonstrated by the determination of the selected drugs in both pure and in commercial dosage forms and has met the validation requirements.
关键词： Spectrophotometry,Timolol,Atenolol,Dosage forms,Potassium permanganate
更新于2025-09-10 09:29:36
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Inorganic Salts and Antimicrobial Photodynamic Therapy: Mechanistic Conundrums?
摘要： We have recently discovered that the photodynamic action of many different photosensitizers (PSs) can be dramatically potentiated by addition of a solution containing a range of different inorganic salts. Most of these studies have centered around antimicrobial photodynamic inactivation that kills Gram-negative and Gram-positive bacteria in suspension. Addition of non-toxic water-soluble salts during illumination can kill up to six additional logs of bacterial cells (one million-fold improvement). The PSs investigated range from those that undergo mainly Type I photochemical mechanisms (electron transfer to produce superoxide, hydrogen peroxide, and hydroxyl radicals), such as phenothiazinium dyes, fullerenes, and titanium dioxide, to those that are mainly Type II (energy transfer to produce singlet oxygen), such as porphyrins, and Rose Bengal. At one extreme of the salts is sodium azide, that quenches singlet oxygen but can produce azide radicals (presumed to be highly reactive) via electron transfer from photoexcited phenothiazinium dyes. Potassium iodide is oxidized to molecular iodine by both Type I and Type II PSs, but may also form reactive iodine species. Potassium bromide is oxidized to hypobromite, but only by titanium dioxide photocatalysis (Type I). Potassium thiocyanate appears to require a mixture of Type I and Type II photochemistry to ?rst produce sul?te, that can then form the sulfur trioxide radical anion. Potassium selenocyanate can react with either Type I or Type II (or indeed with other oxidizing agents) to produce the semi-stable selenocyanogen (SCN)2. Finally, sodium nitrite may react with either Type I or Type II PSs to produce peroxynitrate (again, semi-stable) that can kill bacteria and nitrate tyrosine. Many of these salts (except azide) are non-toxic, and may be clinically applicable.
关键词： potassium thiocyanate,potentiation by inorganic salts,potassium bromide,potassium iodide,sodium azide,antimicrobial photodynamic inactivation,potassium selenocyanate,sodium nitrite
更新于2025-09-09 09:28:46
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Adsorption and Photocatalytic Degradation of Methylene Blue Using Potassium Polytitanate and Solar Simulator
摘要： Solar photocatalytic degradation of organic water pollutants can be used to degrade toxic organic pollutants in water. In this study, potassium titanate nanofibres were synthesized by an aqueous peroxide route at high pH and examined as photocatalysts for photodegradation of methylene blue (MB) using a solar simulator. Initially, MB was adsorbed on the surface of potassium polytitanates to achieve adsorption equilibrium before the photocatalysts were illuminated using solar simulator. The results showed that potassium polytitanate nanofibres were effective adsorbents of MB and also facilitated its photocatalytic degradation. Sulphate ion evolution during photocatalysis confirmed that some mineralisation occurred and hence photo-oxidative degradation of MB took place. The optimum operational conditions for the photocatalytic degradation of MB were found at 0.05 g/L of photocatalyst load, 10 mg/L MB and pH 7. The stability and regeneration of the photocatalyst specimen was also studied for 3 degradation cycles using adsorption/photocatalysis model. Morphological structure analysis of potassium titanate showed nanocrystallines structure of longitudinally-oriented isolated fibre with a length up to several micrometres with diameters ranging from 10 to 20 nanometres.
关键词： Methylene Blue,Photocatalysis,Adsorption,Potassium Polytitanate
更新于2025-09-09 09:28:46
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Remote Ischemia Influences the Responsiveness of the Retina: Observations in the Rat
摘要： Remote ischemic preconditioning (RIP) has been found to be protective of heart and brain against ischemic injury. We have tested the effects of RIP on retinal function using the electroretinogram. METHODS. Ischemia remote from the retina was induced in one hindlimb, using a pressure cuff applied for between 5 and 10 minutes. A temperature probe on the footpad con?rmed blockage of the circulation. To test the impact of RIP on retinal function, we recorded the dark-adapted ?ash electroretinogram (ERG) in four groups (n ? 5 per group) of Sprague-Dawley rats (sham, 5-minute, 10-minute, and 2 3 5-minute ischemia). Heart rate, breath rate, and peripheral oxygen saturation were monitored using infrared pulse oximetry. RESULTS. RIP increased both the a- and b-waves by up to 14%, more markedly after the longer periods (10 minutes or 2 3 5 minutes) of ischemia. The effect was tested up to 30 minutes after ischemia and retested at 1 week and 1 month. RIP did not appear to accelerate the initial stages of recovery from photopigment bleach. Systemic oxygen saturation, heart rate, and respiration did not vary consistently during or after remote ischemia. CONCLUSIONS. The effect of RIP on the ERG is a novel ?nding. Possible mechanisms of this effect are discussed and related to the idea of neuroprotection and to fundamentals of the electroretinogram.
关键词： remote ischemic preconditioning,ATP-sensitive potassium channel,dark adaptation,adenosine,electroretinogram,retina
更新于2025-09-09 09:28:46
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FRET-based imaging of intracellular ATP in organotypic brain slices
摘要： Active neurons require a substantial amount of adenosine triphosphate (ATP) to re‐establish ion gradients degraded by ion flux across their plasma membranes. Despite this fact, neurons, in contrast to astrocytes, do not contain any significant stores of energy substrates. Recent work has provided evidence for a neuro‐metabolic coupling between both cell types, in which increased glycolysis and lactate production in astrocytes support neuronal metabolism. Here, we established the cell type‐specific expression of the F?rster resonance energy transfer (FRET) based nanosensor ATeam1.03YEMK (“Ateam”) for dynamic measurement of changes in intracellular ATP levels in organotypic brain tissue slices. To this end, adeno‐associated viral vectors coding for Ateam, driven by either the synapsin‐ or glial fibrillary acidic protein (GFAP) promoter were employed for specific transduction of neurons or astrocytes, respectively. Chemical ischemia, induced by perfusion of tissue slices with metabolic inhibitors of cellular glycolysis and mitochondrial respiration, resulted in a rapid decrease in the cellular Ateam signal to a new, low level, indicating nominal depletion of intracellular ATP. Increasing the extracellular potassium concentration to 8 mM, thereby mimicking the release of potassium from active neurons, did not alter ATP levels in neurons. It, however, caused in an increase in ATP levels in astrocytes, a result which was confirmed in acutely isolated tissue slices. In summary, our results demonstrate that organotypic cultured slices are a reliable tool for FRET‐based dynamic imaging of ATP in neurons and astrocytes. They moreover provide evidence for an increased ATP synthesis in astrocytes, but not neurons, during periods of elevated extracellular potassium concentrations.
关键词： metabolism,ATeam1.03YEMK,hippocampus,potassium,pH,chemical ischemia
更新于2025-09-09 09:28:46
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Investigation into the room temperature creep-deformation of potassium dihydrogen phosphate crystals using nanoindentation
摘要： It has been a tremendous challenge to manufacture damage-free and smooth surfaces of potassium dihydrogen phosphate (KDP) crystals to meet the requirements of high-energy laser systems. The intrinsic issue is whether a KDP crystal can be plastically deformed so that the material can be removed in a ductile mode during the machining of KDP. This study investigates the room temperature creep-deformation of KDP crystals with the aid of nanoindentation. A stress analysis was carried out to identify the creep mechanism. The results showed that KDP crystals could be plastically deformed at the nano-scale. Dislocation motion is responsible for creep-deformation. Both creep rate and creep depth decrease with decrease in peak force and loading rate. Dislocation nucleation and propagation bring about pop-ins in the load-displacement curves during nanoindentation.
关键词： Dislocation,Potassium dihydrogen phosphate (KDP) crystals,Creep-deformation,Stress
更新于2025-09-09 09:28:46
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Optical Clearing in the Kidney Reveals Potassium-Mediated Tubule Remodeling
摘要： Saritas et al. use optical clearing, immunolabeling, and advanced light microscopy to assess potassium-mediated tubule remodeling in adult mouse kidneys. A low-potassium diet induced proliferation in specific tubule segments, including the distal convoluted tubule, and deletion of the renal potassium sensor Kir4.1 led to shortening of the distal convoluted tubule.
关键词： tubule remodeling,Kir4.1,potassium,kidney,optical clearing
更新于2025-09-09 09:28:46
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Benzo-15-crown-5 (2,3,5,6,8,9,11,12-octahydrobenzo[b] [1,4,7,10,13]pentaoxacyclopentadecine) and dibenzo-15-crown-5 (6,7,9,10,17,18-hexahydrodibenzo[b,h] [1,4,7,10,13] pentaoxacyclopentadecine as fluorescent probes for physiologically important potassium ion
摘要： Cation recognition plays a vital role in defining advanced functions of macromolecules in nature. An example of such an interaction is the action of a natural antibiotic, valinomycin, that behaves as a potassium ionophore. It encages the cation to transport it across a cell membrane and easily releases it inside the cell. Macrocyclic complexes of some crown ethers mimick alkali ion interactions with natural ionophores. We have synthesized complexes of two crown ethers namely benzo-15-crown-5 (2,3,5,6,8,9,11,12-octahydrobenzo[b][1,4,7,10,13] pentaoxacyclopentadecine) and dibenzo-15-crown-5 (6,7,9,10,17,18-hexahydrodibenzo[b,h][1,4,7,10,13]pentaoxacyclopentadecine with potassium halides (fluoride, chloride, bromide and iodide) in acetonitrile and characterized them by IR, UV, ESI-MS, 1H NMR and 13C NMR techniques. The effect of the anion on the stability of the complexes was observed by 1H NMR studies. The alkali metal ion is held to the oxygen donor atoms of the macrocyclic ring by ion-dipole interactions. The potential of the small ring oxacrown ethers, benzo-15-crown-5 and dibenzo-15-crown-5, to act as probes for potassium ions in dilute solutions (4.1 x 10-4 M) was investigated by recording the variation in the fluorescence spectra of benzo-15-crown-5 and dibenzo-15-crown-5 on complexation with potassium fluoride in acetonitrile and chloroform. The rigidity of the macrocyclic ring and proximity of fluorophore units affected the fluorescence intensity of the complexes.
关键词： fluorescence,complexes,macromolecules,cation recognition,potassium,benzo crown
更新于2025-09-09 09:28:46