AM Detection Research Articles

Design, synthesis, and characterization of molecularly imprinted solid phase extraction for alpha Mangostin analysis in blood sample

AbstractLow levels of α‐mangostin (AM) in biological fluids require adequate sample preparation to be analyzed. Molecularly imprinted polymers can serve as sorbents in solid phase extraction, enabling concentration and extraction of α‐mangostin from complex matrices, such as biological fluids. To date, there are no molecular imprinted polymers for the analysis of α‐mangostin in biological fluids. In this study, AM molecular imprinted polymer (MIP) was designed using molecular modeling, molecular dynamic simulations, and prepared by bulk polymerization and suspension polymerization methods. The geometry optimization results showed that acrylamide (AAM) monomer forms the most stable complex with AM at the pre‐polymerization with the most negative Gibbs free energy (ΔG) of −6.91818 Kcal/mol. Radial distribution function (RDF) in molecular dynamics simulation of AM:AAM:ethylene glycol dimethacrylate (EGDMA) with mol ratio 1:4:20 shows the complex with the best composition through the formation of four stable hydrogen bonds. Based on the experimental results, molecularly imprinted polymers in suspension exhibit better characteristics, selectivity, and adsorption capacity than in bulk. The suspension polymerization method showed a high recovery (85.88% ± 2.5), which was higher than C18 SPE cartridge (24.19% ± 1.47). Hence, it can be concluded that the MIPs from MD simulations were accessible and could be used in practice, such as in the separation and detection of AM in blood serum.

Recent progress in electrochemical detection of amaranth in food samples: A brief review

Amaranth (E 123, AM) is a red synthetic azo dye authorized as a food additive in the EU. In contrast to natural colorants, AM has significant advantages such as low production cost, excellent water solubility, and high stability. AM is used to enhance the natural color, to decrease the loss of color due to processing treatments, and to provide color to colorless ultra-processed foods, making food more attractive to the consumers. AM is widely used in food industry to improve the appearance and color of different types of food and beverages, including confectionery products, jelly, candies, jams, dairy products, ice creams, sausages, wines, syrups and soft drinks. Many of these food products are manufactured directly for, and marketed directly to, children. The high amount of AM in food products can cause adverse health effects such as dizziness, allergies, and respiratory problems. Moreover, long-term studies indicated that the potential adverse effects induced by AM include genotoxicity and cytotoxicity. Therefore, the development of a precise and easy-to-handle alternative for a quick and efficient quantitative detection of AM in food products is necessary for consumer safety. Modern electroanalytical techniques have the advantages of excellent sensitivity and selectivity, instrumental simplicity and portability, providing reliable alternatives to the conventional analytical methods. In this brief review, we have summarized recent trends in the electrochemical sensor systems applied for the analysis of AM in food samples, critically evaluated the performance metrics of these sensors: sensitivity, linear range, limit of detection and stability. Finally, the current challenges and future prospects are outlined.

Adenomyomas of the Gallbladder: An Analysis of Frequency, Clinicopathologic Associations, and Relationship to Carcinoma of a Malformative Lesion.

The nature and associations of gallbladder (GB) "adenomyoma" (AM) remain controversial. Some studies have attributed up to 26% of GB carcinoma to AMs. To examine the true frequency, clinicopathologic characteristics, and neoplastic changes in GB AM. Cholecystectomy cohorts analyzed were 1953 consecutive cases, prospectively with specific attention to AM; 2347 consecutive archival cases; 203 totally embedded GBs; 207 GBs with carcinoma; and archival search of institutions for all cases diagnosed as AM. Frequency of AM was 9.3% (19 of 203) in totally submitted cases but 3.3% (77 of 2347) in routinely sampled archival tissue. A total of 283 AMs were identified, with a female to male ratio = 1.9 (177:94) and mean size = 1.3 cm (range, 0.3-5.9). Most (96%, 203 of 210) were fundic, with formed nodular trabeculated submucosal thickening, and were difficult to appreciate from the mucosal surface. Four of 257 were multifocal (1.6%), and 3 of 257 (1.2%) were extensive ("adenomyomatosis"). Dilated glands (up to 14 mm), often radially converging to a point in the mucosa, were typical. Muscle was often minimal, confined to the upper segment. Nine of 225 (4%) revealed features of a duplication. No specific associations with inflammation, cholesterolosis, intestinal metaplasia, or thickening of the uninvolved GB wall were identified. Neoplastic change arising in AM was seen in 9.9% (28 of 283). Sixteen of 283 (5.6%) had mural intracholecystic neoplasm; 7 of 283 (2.5%) had flat-type high-grade dysplasia/carcinoma in situ. Thirteen of 283 cases had both AM and invasive carcinoma (4.6%), but in only 5 of 283 (1.8%), carcinoma arose from AM (invasion was confined to AM, and dysplasia was predominantly in AM). AMs have all the features of a malformative developmental lesion, and may not show a significant muscle component (ie, the name "adeno-myoma" is partly a misnomer). While most are innocuous, some pathologies may arise in AMs, including intracholecystic neoplasms, flat-type high-grade dysplasia or carcinoma in situ, and invasive carcinoma (1.8%, 5 of 283). It is recommended that gross examination of GBs include serial slicing of the fundus for AM detection and total submission if one is found.

The effect of recreational noise exposure on amplitude-modulation detection, hearing sensitivity at frequencies above 8 kHz, and perception of speech in noise.

Psychoacoustic and speech perception measures were compared for a group who were exposed to noise regularly through listening to music via personal music players (PMP) and a control group without such exposure. Lifetime noise exposure, quantified using the NESI questionnaire, averaged ten times higher for the exposed group than for the control group. Audiometric thresholds were similar for the two groups over the conventional frequency range up to 8 kHz, but for higher frequencies, the exposed group had higher thresholds than the control group. Amplitude modulation detection (AMD) thresholds were measured using a 4000-Hz sinusoidal carrier presented in threshold-equalizing noise at 30, 60, and 90 dB sound pressure level (SPL) for modulation frequencies of 8, 16, 32, and 64 Hz. At 90 dB SPL but not at the lower levels, AMD thresholds were significantly higher (worse) for the exposed than for the control group, especially for low modulation frequencies. The exposed group required significantly higher signal-to-noise ratios than the control group to understand sentences in noise. Otoacoustic emissions did not differ for the two groups. It is concluded that listening to music via PMP can have subtle deleterious effects on speech perception, AM detection, and hearing sensitivity over the extended high-frequency range.

Screening of rosmarinic acid from Salvia miltiorrhizae acting on the novel target TRPC1 based on the ‘homology modelling–virtual screening–molecular docking–affinity assay–activity evaluation’ method

Context Salvia miltiorrhizae Bunge (Lamiaceae) is a traditional Chinese medicine (TCM) for the treatment of ‘thoracic obstruction’. Transient receptor potential canonical channel 1 (TRPC1) is a important target for myocardial injury treatment. Objective This work screens the active component acting on TRPC1 from Salvia miltiorrhizae. Materials and methods TCM Systems Pharmacology Database and Analysis Platform (TCMSP) was used to retrieve Salvia miltiorrhiza compounds for preliminary screening by referring to Lipinski’s rule of five. Then, the compound group was comprehensively scored by AutoDock Vina based on TRPC1 protein. Surface plasmon resonance (SPR) was used to determine the affinity of the optimal compound to TRPC1 protein. Western blot assay was carried out to observe the effect of the optimal compound on TRPC1 protein expression in HL-1 cells, and Fura-2/AM detection was carried out to observe the effect of the optimal compound on calcium influx in HEK293 cells. Results Twenty compounds with relatively good characteristic parameters were determined from 202 compounds of Salvia miltiorrhiza. Rosmarinic acid (RosA) was obtained based on the molecular docking scoring function. RosA had a high binding affinity to TRPC1 protein (KD value = 1.27 µM). RosA (50 μM) could reduce the protein levels (417.1%) of TRPC1 after oxygen-glucose deprivation/reperfusion (OGD/R) in HL-1 cells and it could inhibit TRPC1-mediated Ca2+ influx injury (0.07 ΔRatio340/380) in HEK293 cells. Discussion and conclusions We obtained the potential active component RosA acting on TRPC1 from Salvia miltiorrhizae, and we speculate that RosA may be a promising clinical candidate for myocardial injury therapy.

Measuring harmonic benefit in musicians and non-musicians in several tasks

Prior work has demonstrated that harmonic tones are easier to detect in noise and yield better F0 discrimination in noise than inharmonic tones. These effects, referred to as harmonic benefit, appear to be approximately the same size in musicians and non-musicians, despite musicians’ overall better pitch discrimination. The present study aimed to replicate these findings and extend them to include measurements of harmonic benefit in other tasks. Non-musicians and musicians were compared in four tasks: detection in noise, F0 discrimination, FM detection, and AM detection. The stimuli in each task were either harmonic or inharmonic complex tones and were presented in threshold-equalizing noise at a range of signal-to-noise ratios. We found that harmonic benefit for F0 discrimination was large and remained large even after accounting for differences in the detectability of harmonic and inahrmonic tones. In contrast, harmonic benefit was small for FM and AM detection and could mostly be accounted for by differences in detectability. In contrast to prior studies, we found that musicians showed a larger harmonic benefit than non-musicians. These results provide insight into how musical training may specialize the auditory system for processing of harmonicity and pitch. [Work supported by NIH grants F31 DC019247 and R01 DC005216.]

Conversion of amplitude modulation to phase modulation in the human cochlea

When an amplitude modulated signal with a constant-frequency carrier is fed into a generic nonlinear amplifier, the phase of the carrier of the output signal is also modulated. This phenomenon is referred to as amplitude-modulation-to-phase-modulation (AM-to-PM) conversion and regarded as an unwanted signal distortion in the field of electro-communication engineering. Herein, we offer evidence that AM-to-PM conversion also occurs in the human cochlea and that listeners can use the PM information effectively to process the AM of sounds. We recorded otoacoustic emissions (OAEs) evoked by AM signals. The results showed that the OAE phase was modulated at the same rate as the stimulus modulation. The magnitude of the AM-induced PM of the OAE peaked generally around the stimulus level corresponding to the compression point of individual cochlear input–output functions, as estimated using a psychoacoustic method. A computational cochlear model incorporating a nonlinear active process replicates the abovementioned key features of the AM-induced PM observed in OAEs. These results indicate that AM-induced PM occurring at the cochlear partition can be estimated by measuring OAEs. Psychophysical experiments further revealed that, for individuals with higher sensitivity to PM, the PM magnitude is correlated with AM-detection performance. This result implies that the AM-induced PM information cannot be a dominant cue for AM detection, but listeners with higher sensitivity may partly rely on the AM-induced PM cue.

Electrochemical detector based on a modified graphite electrode with phthalocyanine for the elemental analysis of actinides

The quantification of actinides in aqueous solutions involves complex and expensive separation processes. Electrochemical methods have been widely used for the quick and accurate identification and quantification of organic and inorganic compounds directly or indirectly. Therefore, this work proposes the use of modified graphite with phthalocyanine for electrochemical detection and quantification of Th, U, Pu, Am, and Cm, in aqueous media by cyclic voltammetry. The electrodes were characterized by Raman and infrared spectroscopy, and the cyclic voltammetry data were modeled with Aoki’s model. The detection limits (DL) and the quantification limits (QL) reached by the electrochemical detection of these actinides were of the order of ppt. Aoki’s model fitted perfectly with the experimental data. The functionalization of graphite electrodes promotes the formation of phthalic anhydride, and the phthalocyanine is anchored on the epoxy groups of the graphite. The electrochemical detection process of these actinides is indirect. This electrochemical detector is cheap and disposable and can be an alternative for an initial characterization of actinides in liquid waste.

Ultra-sensitive detection of ampicillin via dual-enzyme mediated cascade-signal amplified aptasensor

Herein, an ultra-sensitive aptasensor based on dual-enzyme mediated cascade- signal amplification (dubbed Demcsa aptasensor) for ampicillin (AMP) detection is proposed. The sensor’s activity involves two major steps, i.e., DNA ligase-assisted Exonuclease III (Exo III) catalyzed degradation reaction in a homogeneous solution, signal generation/amplification through the biotin-streptavidin linkage and hybridization chain reaction (HCR) on a 96-well polystyrene plate. Firstly, a detection probe was formed via the hybridization reaction between biotinylated AMP aptamer (bio-AP), HCR initiator strand (H strand) and complementary DNA (cDNA). As a result of the dual-enzyme mediated degradation, a long APH strand was formed via the DNA ligase-catalyzed ligation of bio-AP and the H strand, which served as integrated initiator to trigger the HCR reaction, thereby producing a long double-stranded DNA polymer. Subsequently, the SYBR Green I, as fluorescent dye for DNA, was added and a strong fluorescence signal was generated. In the presence of AMP, the function of DNA ligase was effectively suppressed due to the higher affinity of target-AP strand complex. As a result, the HCR reaction could not be triggered without generating a fluorescence signal, because the bio-AP cannot ligate to the H strand even when captured on the plate. The cascade- signal amplification of biotin-streptavidin linkage and the HCR reaction endowed the Demcsa aptasensor with a limit of detection (LOD) of aM, which was comparable or superior to those of the previously reported sensors. The Demcsa aptasensor has been used for the screening of AMP in food samples with favorable recoveries. The results of this work pave a new, universal way for developing efficient sensors for the detection of other trace food hazards.

Hepatocellular carcinoma cell apoptosis induced by low-intensity ultrasound with polylactic acid-polyethylene glycol nanometer microspheres loaded with sodium cantharidin: An in vitro study

This study examines the synergistic inhibitory effect of two drugs on hepatocellular carcinoma cells using polylactic acid-polyethylene glycol (PLA-PEG) nanoparticles loaded with sodium cantharidin (SCA) combined with low-intensity ultrasound. We sought to provide an experimental basis for the cytological level of SCA combined with low-intensity ultrasound tumor treatment. The study consisted of four treatment groups: HepG2 cells treated with 2.5 g/mL SCA for 30 min then irradiated with 0.5 w/cm2 low-intensity ultrasound for 8 s (combination group), HepG2 cells treated with SCA alone (SCA group), HepG2 cells randomly irradiated with low-intensity ultrasound (ultrasound group), and HepG2 cells without intervention (control group). After each treatment, the cells were cultured for 6 h, and then the cell proliferation inhibition rate, apoptosis cycle, and intracellular calcium concentration were detected using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry and Fluo-3 AM detection. Intracellular ultrastructural changes were observed using transmission electron microscopy. The results showed that the proliferation inhibition rate of cells in the combination group was significantly higher than that in the SCA and ultrasound groups. Annexin V-FITC and propidium iodide staining revealed that the apoptosis rate of the combination group significantly increased compared with that of the other groups. There was no significant difference in cell cycle among the different treatments after 6 h of cell culture. However, cell cycle arrest occurred in HepG2 cells at G0/G1 stage after 12 h of cell culture. Fluo-3 AM showed that the intracellular calcium concentration in the combined group was significantly higher than that in the other groups at 6 h after treatment. Transmission electron microscopy showed that apoptotic bodies and mitochondrial and endoplasmic reticulum swelling were present in the combined group after treatment. We conclude that low-intensity ultrasound (0.5 w/cm2) combined with SCA (2.5 μg/mL) synergistically induce apoptosis of hepatocellular carcinoma HepG2 cells, block cell cycle at G0/G1 phase, and disrupt intracellular calcium homeostasis. PLA-PEG can be loaded with SCA to improve drug targeting and drug concentration in the affected area.

Calcium Signaling and Contractility in Cardiac Myocyte of Wolframin Deficient Rats.

Wolframin (Wfs1) is a membrane protein of the sarco/endoplasmic reticulum. Wfs1 mutations are responsible for the Wolfram syndrome, characterized by diabetic and neurological symptoms. Although Wfs1 is expressed in cardiac muscle, its role in this tissue is not clear. We have characterized the effect of invalidation of Wfs1 on calcium signaling-related processes in isolated ventricular myocytes of exon5-Wfs1 deficient rats (Wfs1-e5/-e5) before the onset of overt disease. Calcium transients and contraction were measured in field-stimulated isolated myocytes using confocal microscopy with calcium indicator fluo-3 AM and sarcomere length detection. Calcium currents and their calcium release-dependent inactivation were characterized in whole-cell patch-clamp experiments. At 4 months, Wfs1-e5/-e5 animals were euglycemic, and echocardiographic examination revealed fully compensated cardiac function. In field-stimulated isolated ventricular myocytes, both the amplitude and the duration of contraction of Wfs1-e5/-e5 animals were elevated relative to control Wfs1+/+ littermates. Increased contractility of myocytes resulted largely from prolonged cytosolic calcium transients. Neither the amplitude of calcium currents nor their voltage dependence of activation differed between the two groups. Calcium currents in Wfs1-e5/-e5 myocytes showed a larger extent of inactivation by short voltage prepulses applied to selectively induce calcium release-dependent inactivation of calcium current. Neither the calcium content of the sarcoplasmic reticulum, measured by application of 20 mmol/l caffeine, nor the expression of SERCA2, determined from Western blots, differed significantly in myocytes of Wfs1-e5/-e5 animals compared to control ones. These experiments point to increased duration of calcium release in ventricular myocytes of Wfs1-e5/-e5 animals. We speculate that the lack of functional wolframin might cause changes leading to upregulation of RyR2 channels resulting in prolongation of channel openings and/or a delay in termination of calcium release.

Spectroscopic speciation of aqueous Am(iii)-oxalate complexes.

Transportation of actinides through the geosphere is facilitated by complexation with organic ligands dissolved in groundwater. Carboxylic groups can interact directly with actinide ions and are found among the most abundant organic ligands in alkaline aquatic systems like underground water. In this study, the complexation of organic carboxylic groups with Am(iii) was investigated by monitoring the interactions of Am(iii) with oxalate (Ox), the simplest dicarboxylate ligand, in solution. UV-Vis spectrophotometry coupled with a liquid waveguide capillary cell (100 cm optical path-length) and time-resolved laser fluorescence spectroscopy were employed for quantitative detection of the respective Am(iii)-Ox species. Increasing the Ox concentration caused significant spectral changes, i.e., red-shifts in both the absorption and luminescence maxima with increased molar absorption coefficients, enhanced luminescence intensities, and prolonged luminescence lifetimes. Individual spectra of AmOx+(aq), Am(Ox)2-(aq), and Am(Ox)33-(aq) were resolved by deconvolution of the absorption spectra, with apparent formation constants of log β1,1 = 5.34 ± 0.05, log β1,2 = 9.14 ± 0.18, and log β1,3 = 11.49 ± 0.30, respectively, in I = 0.1 M NaClO4 and 0-30 mM Na2Ox. The absorption and luminescence spectral changes suggest bidentate complexation of Ox with Am(iii) via inner-sphere interactions. The geometry of the Am(iii)-Ox complexes was optimized by density functional theory, where the bonding characteristics were in good agreement with the experimental results. Thorough spectroscopic characterization enabled speciation of the Am(iii)-Ox complexes and determination of their formation constants. This spectroscopic approach is generally applicable in the investigation of molecular interactions between Am(iii) and various ligands in aqueous solution.

Graphene nanoribbon/FePt bimetallic nanoparticles/uric acid as a novel magnetic sensing layer of screen printed electrode for sensitive determination of ampyra

A novel electrochemical sensor for sensitive determination of ampyra (Am) based on graphene nanoribbons modified by iron-platinum bimetallic nanoparticles and uric acid (SPCE/FePtGNR/UA) dropped on the screen-printed carbon electrode (SPCE) surface and magnetically captured onto an SPCE working electrode surface is reported in the present work. The modified nanocomposite and sensing layer was characterized by different techniques, including cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray powdered diffraction (XRD). Am determination by conventional electrochemical methods is not possible, because of its high redox overpotential. Therefore, the differential pulse voltammetry (DPV) signals of UA were used as a redox probe for indirect electrochemical determination of Am. The limit of detection (LOD) and linear concentration range were obtained as 0.028 and 0.08–9.0µmolL−1 (3Sb/m = 3), respectively. The feasibility of the proposed method was examined by the detection of Am in biological and pharmaceutical samples with satisfactory results. The constructed electrochemical sensor was applied for fast, simple and sensitive detection of Am in real environments.

Fabrication of a novel impedimetric sensor based on l-Cysteine/Cu(II) modified gold electrode for sensitive determination of ampyra

This paper presents a novel impedimetric sensor for the sensitive determination of ampyra (Am) based on the l-Cysteine/Cu (II) modified gold electrode (Cu (II)/L-Cys/AuE). This novel sensing layer was characterized by different techniques, including atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Am determination by conventional electrochemical methods is not possible, because of its high redox overpotential. Therefore, [Fe(CN)6]3-/4- was used as a redox probe for the impedimetric determination of Am. Under the optimized conditions, the calibration curve for Am concentration was linear in the range 0.010–40.0 nM with a detection limit of 0.0028 nM. The practical applicability of the proposed sensor was examined by evaluating the detection of Am in biological fluids and pharmaceutical samples with satisfied recoveries. Therefore, the prepared sensor can hold great promise for fast, simple and sensitive detection of Am in various real samples.

Bacterial Endocarditis in an Intravenous Drug User with a Ventricular Septal Aneurysm

An aneurysm of the membranous portion of the ventricular septum (AMS) is a common complication of spontaneous ventricular septal defect closure. They have been shown to increase the incidence of cardiac pathology notably bacterial endocarditis. Because of such a severe threat, it may be an important anomaly to assess in high risk patients. A 45-year-old woman with a history of intravenous drug use presented in septic shock with end organ damage requiring intubation, broad spectrum antibiotics, and vasopressors. Physical examination displayed a 2/6 systolic ejection murmur heard loudest at the left lower sternal border. Echocardiography confirmed a mobile tricuspid vegetation; as well as, an aneurysmal deformity. During her initial history the patient stated that her VSD had been diagnosed in childhood. A cardiac catheterization showed a membranous ventricular septal aneurysm protruding from the left ventricle into the right ventricle with no evidence of ventricular septal defect. This case exemplifies a patient predisposed to endocarditis who was at higher risk due to her actions. The objective contribution of the AMS to the resultant endocarditis is unknown at this point. This sentiment raises the question if AMS detection would warrant preventative intervention for associated pathologies.

Sensorineural hearing loss enhances auditory sensitivity and temporal integration for amplitude modulation.

Amplitude-modulation detection thresholds (AMDTs) were measured at 40 dB sensation level for listeners with mild-to-moderate sensorineural hearing loss (age: 50-64 yr) for a carrier frequency of 500 Hz and rates of 2 and 20 Hz. The number of modulation cycles, N, varied between two and nine. The data were compared with AMDTs measured for young and older normal-hearing listeners [Wallaert, Moore, and Lorenzi (2016). J. Acoust. Soc. Am. 139, 3088-3096]. As for normal-hearing listeners, AMDTs were lower for the 2-Hz than for the 20-Hz rate, and AMDTs decreased with increasing N. AMDTs were lower for hearing-impaired listeners than for normal-hearing listeners, and the effect of increasing N was greater for hearing-impaired listeners. A computational model based on the modulation-filterbank concept and a template-matching decision strategy was developed to account for the data. The psychophysical and simulation data suggest that the loss of amplitude compression in the impaired cochlea is mainly responsible for the enhanced sensitivity and temporal integration of temporal envelope cues found for hearing-impaired listeners. The data also suggest that, for AM detection, cochlear damage is associated with increased internal noise, but preserved short-term memory and decision mechanisms.

Energy-Efficient Digital Front-End Processor for 60 GHz Polar Transmitter

This paper presents an energy-efficient digital front-end processor for digital-intensive polar transmitter architecture working on 60 GHz band in standard 28nm CMOS process. This avoids modulating the supply and also eliminates the need of an additional RF limiter and AM detection circuits in the traditional analog-centric polar transmitter architecture. The design challenges on the digital signal processing (DSP) front-end are analyzed and tackled. The systematic optimizations are first explored to minimize the design requirements on the DSP front-end. A pulse shaping filter is designed to shape the frequency spectrum of the quadrature signals so that the signal at the output of the filter is compliant with the spectrum mask requirements. Instead of using computation-intensive raised cosine filter for the pulse shaping, we use poly-phase Cascaded Integrator-Comb (CIC) filter to shape the spectrum. Parallel rotation and vectoring COordinate Rotation DIgital Computers (CORDICs) are designed to perform rectangular-to-polar conversion. Furthermore, a pre-distortion circuit based on look-up table (LUT) is designed to compensate the power amplifier (PA) nonlinearities. Taylor’s approximation is explored to avoid the complex trigonometric computation in the pre-distortion. Finally, an efficient latch-based pipeline is studied to provide the required 7.04 Gsps throughput with less than 60 mW. The synthesis results compare favorably with previously reported architectures.

Quality Improvement

Quality Improvement

Fast Amplitude Modulation Detector for Scanning Force Microscopy with High Q Factor

Amplitude modulation (AM) scanning force microscopy (SFM) is superior to frequency modulation SFM in simplicity, sensitivity, and stability, but is still replaced by the latter because it is too slow when the Q factor is high (bandwidth < 0.5 Hz for Q > 50,000 and resonant frequency ω0 < 50 kHz). We report a close-loop AM detector that has an 18 Hz bandwidth, better than 1 mHz frequency resolution and excellent response to step frequency changes even for Q ∼ 60,000 and ω0 ∼ 32 kHz. Its superiority is well shown by the comparison of magnetic force microscope images taken under the new and old AM detection modes with the tip and scan area (videotape sample) being unchanged. Also important is that shifting the driving frequency from near the resonance peak to further away from the peak does not decrease the frequency resolution as much as we expect (but can increase the response speed).

Zr–Nb isobar separation experiments for future 93Zr AMS

AMS detection of the rare isotope 93Zr (t1/2=1.6Ma) has application potential in two fields of research: a better determination of the 92Zr(n,γ)93Zr cross section, which is relevant in astrophysical modeling of nucleosynthesis processes, and using this radionuclide as tracer in hydrological and radioactive waste studies. The biggest challenge in measuring 93Zr at natural concentrations is adequate separation from its stable isobar 93Nb. The Nuclear Science Laboratory at the University of Notre Dame is developing the capability to measure 93Zr by AMS. Results are reported of first experiments, featuring the combination of a gas-filled magnet with a position-sensitive Parallel Grid Avalanche Counter and a Gas Ionization chamber in this magnet’s focal-plane.