214 research outputs found
Improved spatial separation of neutral molecules
We have developed and experimentally demonstrated an improved electrostatic
deflector for the spatial separation of molecules according to their
dipole-moment-to-mass ratio. The device features a very open structure that
allows for significantly stronger electric fields as well as for stronger
deflection without molecules crashing into the device itself. We have
demonstrated its performance using the prototypical OCS molecule and we discuss
opportunities regarding improved quantum-state-selectivity for complex
molecules and the deflection of unpolar molecules.Comment: 6 figure
Strongly aligned and oriented molecular samples at a kHz repetition rate
We demonstrate strong adiabatic laser alignment and mixed-field orientation
at kHz repetition rates. We observe degrees of alignment as large as
cos\Theta=0.94 at 1 kHz operation for iodobenzene. The experimental setup
consist of a kHz laser system simultaneously producing pulses of 30 fs (1.3 mJ)
and 450 ps (9 mJ). A cold 1 K state-selected molecular beam is produced at the
same rate by appropriate operation of an Even-Lavie valve. Quantum state
selection has been obtained using an electrostatic deflector. A camera and data
acquisition system records and analyzes the images on a single-shot basis. The
system is capable of producing, controlling (translation and rotation) and
analyzing cold molecular beams at kHz repetition rates and is, therefore,
ideally suited for the recording of ultrafast dynamics in so-called "molecular
movies".Comment: 6 pages, 4 figures, in press in Mol. Phys., accepted in February
2013, in final production (galley proofs done) since March 8, 2013, v3 only
adds publication dat
Two-state wave packet for strong field-free molecular orientation
We demonstrate strong laser-field-free orientation of absolute-ground-state
carbonyl sulfide molecules. The molecules are oriented by the combination of a
485-ps-long non-resonant laser pulse and a weak static electric field. The
edges of the laser pulse create a coherent superposition of two rotational
states resulting in revivals of strong transient molecular orientation after
the laser pulse. The experimentally attained degree of orientation of 0.6
corresponds to the theoretical maximum for mixing of the two states. Switching
off the dc field would provide the same orientation completely field-free
The Three Bartlebys of Melville’s Tale
A study of any one of Herman Melville’s works is bound to be a fascinating and informative venture. Within the products of his prolific writing career are keen, precise, enlightening observations about nineteenth-century America. Religion, politics, business, literature, and philosophy are all within the realm of Melville’s careful consideration. Melville was a man who reacted to his world with intense curiosity and passion. Melville was also extremely introspective – searching, questioning, and examining himself with equal intensity.
“Bartleby the Scrivener” offers an interesting synthesis of Melville’s double vision. Within the confines of this tale are Melville’s reaction to his world and his reaction to himself. The purpose of this study is to examine the kaleidoscopic perspective of Melville, the complexity of his world and mind. Examining Bartleby as a simple man, a superman, and the artist in society acknowledges the complexity of Melville’s mind and art and furthers understanding of this particular story, Melville’s others works and Melville himself. Most scholarly considerations of “Bartleby” have centered on one perspective to the exclusion of all others; to do so is a violation of Melville’s purpose, plan and message.
Bartleby is, first of all, considered as a simple man, a fictitious character in a story in relation to other fictitious characters. At this level it is possible to understand how Melville used the basic elements of fiction in his story to show the broad literary motifs with which he was concerned. Within the second level of consideration Bartleby is seen as one of Melville’s supermen, a man who by virtue of his tragic vision, isolated existence, and nonmaterialistic mindset rises above the superficiality, pettiness, and mundane nature of the common man. At the third and final level Bartleby is considered as the artist in society. The autobiographical element in this consideration is extensive. Melville depicts the plight of himself and all creative individuals in modern capitalistic societies, contending that the artist is partially responsible for the intellectual salvation of the common man. The artist’s purpose or quest is to enlighten the understanding of simple men, to help them see the complexity and darkness of reality. Such enlightenment makes supermen out of simple men.
An examination of “Bartleby” at these three levels provides an extensive but not exhaustive analysis of Melville’s story. There are finer shades of meaning and more intricate nuances of thought within the story. The purpose of considering Bartleby as simple man, superman, and artist is to understand the processes of Melville’s mind, the essentials of his thought, and the recurrent patterns of imagery and allusions in his literature. It is to identify the most essential specific themes and ideas in the story and to minimize its complexity and obscurity without sacrificing the richness and depth of Melville’s thought. The study is an attempt to understand and meet Melville as far as possible on his own terms
Strongly driven quantum pendulum of the OCS molecule
We demonstrate and analyze a strongly driven quantum pendulum in the angular
motion of stateselected and laser aligned OCS molecules. Raman-couplings during
the rising edge of a 50-picosecond laser pulse create a wave packet of pendular
states, which propagates in the confining potential formed by the
polarizability interaction between the molecule and the laser field. This
wave-packet dynamics manifests itself as pronounced oscillations in the degree
of alignment with a laser-intensity dependent period.Comment: 6 pages, 4 figure
Photophysics of indole upon x-ray absorption
A photofragmentation study of gas-phase indole (CHN) upon
single-photon ionization at a photon energy of 420 eV is presented. Indole was
primarily inner-shell ionized at its nitrogen and carbon orbitals.
Electrons and ions were measured in coincidence by means of velocity map
imaging. The angular relationship between ionic fragments is discussed along
with the possibility to use the angle-resolved coincidence detection to perform
experiments on molecules that are strongly oriented in their recoil-frame. The
coincident measurement of electrons and ions revealed
fragmentation-pathway-dependent electron spectra, linking the structural
fragmentation dynamics to different electronic excitations. Evidence for
photoelectron-impact self-ionization was observed.Comment: 11 pages, 6 figure
Palliative treatment of uncontrollable hypercalcemia due to parathyrotoxicosis: denosumab as rescue therapy
Parathyroid carcinoma is a rare disease leading to severe hypercalcemia due to hyperparathyroidism. Surgery is the primary treatment option. A more progressive form of the disease is characterized by parathyrotoxicosis, and subsequent hypercalcemia is the most common cause of death. We report a case presenting with severe hypercalcemia due to parathyrotoxicosis from parathyroid carcinoma treated for the first time using the monoclonal antibody denosumab as a rescue therapy and present long-term follow-up data. The 71-year-old patient presented with severe hypercalcemia due to metastatic parathyroid carcinoma. Despite undergoing treatment with bisphosphonates, cinacalcet hydrochloride, and forced diuresis, the patient's condition deteriorated rapidly due to resistant hypercalcemia. Surgery performed because of spinal metastasis and forced diuresis lowered calcium levels, albeit they remained in the hypercalcemic range and significantly increased when forced diuresis was stopped. Considering a palliative situation to overcome hypercalcemia, we decided to administer denosumab, a monoclonal antibody that binds to the receptor activator of nuclear factor-kappa B ligand. After a single subcutaneous administration of 60 mg denosumab, calcium levels normalized within one day. Subsequent denosumab injections led to permanent control of serum calcium for more than 2 years despite rising parathyroid hormone levels and repeated surgeries. Together with recent cases in the literature supporting our observation, we believe that denosumab is relevant for future trials and represents an effective tool to control hypercalcemia in patients with advanced stages of parathyroid cancer
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Conversion of descriptor representations to state-space form: an extension of the shuffle algorithm
This paper proposes a systematic procedure for the determination of state-space models from an available descriptor representation of a linear dynamic system. The goal is to determine a state equation, a set of algebraic equations and an output equation in terms of the state and input variables. It is shown that standard methods may fail to convert the descriptor representation to state-space form, even for simple electrical circuit models obtained from Kirchoff’s laws and constitutive element equations. A novel procedure to address this problem is then proposed as an extension of the classic shuffle algorithm combined with a singular value decomposition approach. In addition to an illustrative example involving a simple electrical circuit, the proposed method is employed in a case study involving the modeling of three-dimensional RLC networks with a large number of components
HL-1 cells express an inwardly rectifying K+ current activated via muscarinic receptors comparable to that in mouse atrial myocytes
An inwardly rectifying K^+ current is present in atrial cardiac myocytes that is activated by acetylcholine (I_{KACh}). Physiologically, activation of the current in the SA node is important in slowing the heart rate with increased parasympathetic tone. It is a paradigm for the direct regulation of signaling effectors by the Gβγ G-protein subunit. Many questions have been addressed in heterologous expression systems with less focus on the behaviour in native myocytes partly because of the technical difficulties in undertaking comparable studies in native cells. In this study, we characterise a potassium current in the atrial-derived cell line HL-1. Using an electrophysiological approach, we compare the characteristics of the potassium current with those in native atrial cells and in a HEK cell line expressing the cloned Kir3.1/3.4 channel. The potassium current recorded in HL-1 is inwardly rectifying and activated by the muscarinic agonist carbachol. Carbachol-activated currents were inhibited by pertussis toxin and tertiapin-Q. The basal current was time-dependently increased when GTP was substituted in the patch-clamp pipette by the non-hydrolysable analogue GTPγS. We compared the kinetics of current modulation in HL-1 with those of freshly isolated atrial mouse cardiomyocytes. The current activation and deactivation kinetics in HL-1 cells are comparable to those measured in atrial cardiomyocytes. Using immunofluorescence, we found GIRK4 at the membrane in HL-1 cells. Real-time RT-PCR confirms the presence of mRNA for the main G-protein subunits, as well as for M2 muscarinic and A1 adenosine receptors. The data suggest HL-1 cells are a good model to study IKAch
Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules
This paper gives an account of our progress towards performing femtosecond
time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe
setup combining optical lasers and an X-ray Free-Electron Laser. We present
results of two experiments aimed at measuring photoelectron angular
distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and
dissociating, laseraligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss
them in the larger context of photoelectron diffraction on gas-phase molecules.
We also show how the strong nanosecond laser pulse used for adiabatically
laser-aligning the molecules influences the measured electron and ion spectra
and angular distributions, and discuss how this may affect the outcome of
future time-resolved photoelectron diffraction experiments.Comment: 24 pages, 10 figures, Faraday Discussions 17
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