A Mechanical Mass Sensor with Yoctogram Resolution

Nanoelectromechanical systems (NEMS) have generated considerable interest as inertial mass sensors. NEMS resonators have been used to weigh cells, biomolecules, and gas molecules, creating many new possibilities for biological and chemical analysis [1-4]. Recently, NEMS-based mass sensors have been employed as a new tool in surface science in order to study e.g. the phase transitions or the diffusion of adsorbed atoms on nanoscale objects [5-7]. A key point in all these experiments is the ability to resolve small masses. Here we report on mass sensing experiments with a resolution of 1.7 yg (1 yg = 10^-24 g), which corresponds to the mass of one proton, or one hydrogen atom. The resonator is made of a ~150 nm long carbon nanotube resonator vibrating at nearly 2 GHz. The unprecedented level of sensitivity allows us to detect adsorption events of naphthalene molecules (C10H8) and to measure the binding energy of a Xe atom on the nanotube surface (131 meV). These ultrasensitive nanotube resonators offer new opportunities for mass spectrometry, magnetometry, and adsorption experiments.Comment: submitted version of the manuscrip

Performance of Monolayer Graphene Nanomechanical Resonators with Electrical Readout

The enormous stiffness and low density of graphene make it an ideal material for nanoelectromechanical (NEMS) applications. We demonstrate fabrication and electrical readout of monolayer graphene resonators, and test their response to changes in mass and temperature. The devices show resonances in the MHz range. The strong dependence of the resonant frequency on applied gate voltage can be fit to a membrane model, which yields the mass density and built-in strain. Upon removal and addition of mass, we observe changes in both the density and the strain, indicating that adsorbates impart tension to the graphene. Upon cooling, the frequency increases; the shift rate can be used to measure the unusual negative thermal expansion coefficient of graphene. The quality factor increases with decreasing temperature, reaching ~10,000 at 5 K. By establishing many of the basic attributes of monolayer graphene resonators, these studies lay the groundwork for applications, including high-sensitivity mass detectors

Setting benchmarks for modelling gas–surface interactions using coherent control of rotational orientation states

A fundamental and predictive understanding of molecule-surface interactions is challenging to obtain. Here the authors report an experimental technique allowing direct measurement of the scattering matrix, which reports on the coherent evolution of quantum states of a molecule scattering from a surface

Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microelecronic devices

Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound ─ morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT) ─ are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm−2 is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics

Dopamine D-1- and D-2-dependent catalepsy in the rat requires functional NMDA receptors in the corpus striatum, nucleus accumbens and substantia nigra pars reticulata

This study investigated the anticataleptic activity of MK-801 versus the D-1 antagonist SCH 23390 and the D-2 antagonist raclopride, using the horizontal bar test in the rat. MK-801, 0.2 mg/kg i.p., strongly opposed the cataleptogenic actions of SCH 23390 and raclopride administered systemically (1 and 3 mg/kg i.p., respectively), or directly into the corpus striatum (CS) or nucleus accumbens (NAc; 1 and 10 mu g, respectively). Conversely, intraCS and intraNAc pretreatment with MK-801 (10 mu g) markedly attenuated the cataleptic response to a systemic injection of SCH 23390 or raclopride. In the latter experiments the anticataleptic effect of MK-801 was pronounced and sustained(>2 h), except with intraCS MK-801 versus raclopride, where it was initially profound but only short-lived (15 min). Stereotaxic injection of MK-801 (1 mu g) into the substantia nigra pars reticulata (SNr) prevented catalepsy developing to either dopamine D-1 or D-2 receptor antagonism. These results indicate there must be unimpeded glutamate neurotransmission in the CS and NAc before catalepsy can develop fully to D-1 and D-2 dopamine receptor blockade in these structures. The weaker glutamate-D-2 interaction in the CS than in the NAc may be related to differences in the N-methyl-D-aspartate receptor subpopulations in these nuclei. Finally, the ability of intranigral MK-801 to diminish both D-1- and D-2-dependent catalepsy suggests the SNr acts as a common output pathway for the expression of both forms of catalepsy in the rat. (C) 1997 Elsevier Science B.V

SYNTHESIS AND ANTICONVULSANT ACTIVITY OF SOME NEW 1,1-BIS(4-SUBSTITUTED 1,2,4-TRIAZOLINE-5-THIONE-3-YL)2-METHYLBUTANES

Several 1,1-bis(4-alkyl/aryl-1,2,4-triazoline-5-thione-3-yl)-2-methylbutane derivatives 13-21 were obtained from the cyclization of mono(1-methylpropyl)malonylbis(4-alkyl/aryl)thiosemicarbazides 2-12 in the presence of sodium hydroxide. Their chemical structures were proven by spectral data (UV, IR, H-1-NMR, MS) and elemental analysis. The anticonvulsant activity of the title compounds were determined against pentylenetetrazole induced seizures. Six of the tested compounds showed anticonvulsant activity (10 to 20% protection)

PHARMACOLOGICAL STUDIES ON QUATERNIZED 4(3H)-QUINAZOLINONES

Locomotor activity-inhibiting, anticonvulsant, muscle relaxant, analgesic, and antimicrobial properties of 2-methyl-3-pyridiniumacetylamino-4(3H)-quinazolinone chloride (1), 2-methyl-3-(4-methylpyridinium)acetylamino-4(3H)-quinazolinone chloride (2), 2-methyl-3-(4-ethylpyridinium)acetylamino-4(3H)-quinazolinone chloride (3), 2-methyl-3-(3-carboxamidopyridinium)acetylamino-4(3H)-quinazolinone chloride (4), and 2-methyl-3-(4-carboxamidopyridinium)acetylamino-4(3H)-quinazolinone chloride (5) were investigated. The locomotor activity-inhibiting properties and anticonvulsant activity of 2 were almost equal to those of methaqualone. The analgesic activities of 2 and 3 in the hot-plate test were equal to that of aspirin, whereas in the Koster test, the analgesic activity of 2 was higher. The compounds did not exhibit antimicrobial or muscle relaxant properties. Most active compounds had higher lipophilicity values than those of inactive compounds

Synthesis and anticonvulsant activity of some new arylidenehydrazides and 4-thiazolidinones

A number of N,N'-bis(arylidene)mono(1-methylpropyl)malonic acid dihydrazides (3a-c), 1,1-bis[[(2-aryl-4-thiazolidinone-3-yl)amino]carbonyl]-2-methylbutanes (4a-e), and 1,1-bis[[3-alkyl/aryl-4-thiazolidinone-2-yl)hydrazono]carbonyl]-2-methylbutanes (6a-i) have been synthesized, characterized and evaluated for anticonvulsant activity. All tested compounds showed significant activity (10 to 60% protection) against pentylenetetrazole induced seizures

Synthesis and antibacterial activity of 5-aryl-2-[(alpha-chloro-alpha-phenylacetyl/alpha-bromopropionyl)amino]-1,3,4-oxadiazoles and 2-[(5-aryl-1,3,4-oxadiazol-2-yl)imino]-5-phenyl/methyl-4-thiazolidinoes

Reaction of 5-aryl-2-amino-1,3,4-oxadiazoles (BI-VI), obtained by the oxydative cyclization of aromatic aldehyde semicarbazones (A(I-VI)), with alpha-chloro-alpha-phenylacetyl chloride and alpha-bromopropionyl bromide yielded 5-aryl-2-[(alpha-chloro-alpha-phenylacetyl)amino]- 1,3,4-oxadiazoles (Ia-VIa) and 5-aryl-2-[(alpha-bromopropionyl)amino]-1,3,4-oxadiazoles (VIIa-XIIa), respectively. Furthermore, Ia-XIIa were refluxed with ammonium thiocyanate to give 5-phenyl/methyl-2-[(5-aryl-1,3,4-oxadiazol-2-yl)imino]-4-thiazolidinones (It-XIIt)