Universal Vectorial and Ultrasensitive Nanomechanical Force Field Sensor

Miniaturization of force probes into nanomechanical oscillators enables ultrasensitive investigations of forces on dimensions smaller than their characteristic length scale. Meanwhile it also unravels the force field vectorial character and how its topology impacts the measurement. Here we expose an ultrasensitive method to image 2D vectorial force fields by optomechanically following the bidimensional Brownian motion of a singly clamped nanowire. This novel approach relies on angular and spectral tomography of its quasi frequency-degenerated transverse mechanical polarizations: immersing the nanoresonator in a vectorial force field does not only shift its eigenfrequencies but also rotate eigenmodes orientation as a nano-compass. This universal method is employed to map a tunable electrostatic force field whose spatial gradients can even take precedence over the intrinsic nanowire properties. Enabling vectorial force fields imaging with demonstrated sensitivities of attonewton variations over the nanoprobe Brownian trajectory will have strong impact on scientific exploration at the nanoscale

Franck-Condon blockade in suspended carbon nanotube quantum dots

Understanding the influence of vibrational motion of the atoms on electronic transitions in molecules constitutes a cornerstone of quantum physics, as epitomized by the Franck-Condon principle of spectroscopy. Recent advances in building molecular-electronics devices and nanoelectromechanical systems open a new arena for studying the interaction between mechanical and electronic degrees of freedom in transport at the single-molecule level. The tunneling of electrons through molecules or suspended quantum dots has been shown to excite vibrational modes, or vibrons. Beyond this effect, theory predicts that strong electron-vibron coupling dramatically suppresses the current flow at low biases, a collective behaviour known as Franck-Condon blockade. Here we show measurements on quantum dots formed in suspended single-wall carbon nanotubes revealing a remarkably large electron-vibron coupling and, due to the high quality and unprecedented tunability of our samples, admit a quantitative analysis of vibron-mediated electronic transport in the regime of strong electron-vibron coupling. This allows us to unambiguously demonstrate the Franck-Condon blockade in a suspended nanostructure. The large observed electron-vibron coupling could ultimately be a key ingredient for the detection of quantized mechanical motion. It also emphasizes the unique potential for nanoelectromechanical device applications based on suspended graphene sheets and carbon nanotubes.Comment: 7 pages, 3 figure

Frequency fluctuations in silicon nanoresonators

Frequency stability is key to performance of nanoresonators. This stability is thought to reach a limit with the resonator's ability to resolve thermally-induced vibrations. Although measurements and predictions of resonator stability usually disregard fluctuations in the mechanical frequency response, these fluctuations have recently attracted considerable theoretical interest. However, their existence is very difficult to demonstrate experimentally. Here, through a literature review, we show that all studies of frequency stability report values several orders of magnitude larger than the limit imposed by thermomechanical noise. We studied a monocrystalline silicon nanoresonator at room temperature, and found a similar discrepancy. We propose a new method to show this was due to the presence of frequency fluctuations, of unexpected level. The fluctuations were not due to the instrumentation system, or to any other of the known sources investigated. These results challenge our current understanding of frequency fluctuations and call for a change in practices

Molecular cloning of an alpha-amylase gene from Bacillus subtilis RSKK246 and its expression in Escherichia coli and in Bacillus subtilis

WOS: 000167987000011Bacillus subtilis RSKK246 was found to produce approximately a 65-kDa alpha -amylase enzyme. A gene was isolated encoding ol-amylase activity that corresponded to this size and was inserted into pUC18 plasmid which was transferred to Escherichia coli. An approximately 1.7kbp fragment, which contains a whole alpha -amylase gene, was excised and inserted into pUB110 and then transferred into the different B. subtilis strains including RSKK246, RSKK243, RSKK244, YB886 and DREAM. The alpha -amylase gene was cloned into the plasmids and expressed with its own promoter, and this promoter sequence seemed to function in the E. coli and in all B. subtilis strains. Specific activity of the cloned enzyme was found to be higher than the native enzyme and molecular weight of the gene product remained the same in all other strains suggesting that it is resistant to the proteolytic attacks of these organisms

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

Protective effects of honokiol on ischemia/reperfusion injury of rat ovary: an experimental study

Senem Yaman Tunc,1 Elif Agacayak,1 Neval Yaman Goruk,2 Mehmet Sait Icen,1 Abdulkadir Turgut,1 Ulas Alabalik,3 Cihan Togrul,4 Cenap Ekinci,5 Aysun Ekinci,6 Talip Gul1 1Department of Obstetrics and Gynecology, School of Medicine, Dicle University, 2Department of Obstetrics and Gynecology, Diyarbakir Memorial Hospital, 3Department of Pathology, School of Medicine, Dicle University, Diyarbakir, 4Department of Obstetrics and Gynecology, School of Medicine, Hitit University, Corum, 5Department of Histology and Embryology, 6Department of Medical Biochemistry, School of Medicine, Dicle University, Diyarbakir, Turkey Aim: The purpose of this study was to investigate the protective effect of honokiol on experimental ischemia/reperfusion injury of rat ovary.Materials and methods: A total of 40 female Wistar albino rats were used in this study. The rats were divided into five groups as follows: sham (Group I), torsion (Group II), torsion + detorsion (Group III), torsion + detorsion + saline (Group IV), and torsion + detorsion + honokiol (Group V). Bilateral adnexa in all the rats except for those in the sham group were exposed to torsion for 3 hours. The rats in Group IV were administered saline, whereas the rats in Group V were administered honokiol by intraperitoneal route 30 minutes before detorsion. Tissue and plasma concentrations of malondialdehyde and nitric oxide were determined. Ovarian tissue was histologically evaluated. Data analyses were performed by means of Kruskal–Wallis test and Mann–Whitney U-test (Bonferroni correction) in SPSS 15.0 (Statistical Package for Social Sciences; SPSS Inc., Chicago, IL, USA).Results: The torsion and detorsion groups had higher scores in vascular congestion, hemorrhage, and inflammatory cell infiltration compared with the sham group (P<0.005). In addition, total histopathological scores were significantly higher in the torsion and detorsion groups compared with the sham group (P<0.005). A significant reduction was observed in hemorrhage, inflammatory cell infiltration, and cellular degeneration scores, of all histopathological scores, in the honokiol group (P<0.005). Ovarian tissue concentrations of malondialdehyde were significantly higher in the torsion and detorsion groups compared with the sham and honokiol groups (P<0.005). Ovarian tissue concentrations of nitric oxide, on the other hand, were significantly higher in the torsion group compared with the sham, saline, and honokiol groups (P<0.005).Conclusion: Honokiol has a beneficial effect on ovarian torsion-related ischemia/reperfusion injury. Keywords: ovary, ischemia/reperfusion injury, honokiol, malondialdehyde, nitric oxide&nbsp