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The structures of gas-phase noncovalently bound clusters have long been studied in supersonic expansions. This method of study, while providing a wealth of information about the nature of noncovalent bonds, precludes observation of the formation of the cluster, as the clusters form just after the orifice of the pulsed valve. Here, we directly observe formation of ethanol-methanol dimers via microwave spectroscopy in a controlled cryogenic environment. Time profiles of the concentration of reagents in the cell yielded gas-phase reaction rate constants of k Me - g = (2.8 ± 1.4) × 10 -13 cm 3 molecule -1 s -1 and k Me - t = (1.6 ± 0.8) × 10 -13 cm 3 molecule -1 s -1 for the pseudo-second-order ethanol-methanol dimerization reaction at 8 K. The relaxation cross section between the gauche and trans conformers of ethanol was also measured using the same technique. In addition, thermodynamic relaxation between conformers of ethanol over time allowed for selection of conformer stoichiometry in the ethanol-methanol dimerization reaction, but no change in the ratio of dimer conformers was observed with changing ethanol monomer stoichiometry.

Using chirped and cavity microwave spectroscopies, automated double resonance, new high-speed fitting and deep learning algorithms, and large databases of computed structures, the discharge products of benzene alone, or in combination with molecular oxygen or nitrogen, have been exhaustively characterized between 6.5 and 26 GHz. In total, more than 3300 spectral features were observed; 89% of these, accounting for 97% of the total intensity, have now been assigned to 152 distinct chemical species and 60 of their variants (i.e., isotopic species and vibrationally excited states). Roughly 50 of the products are entirely new or poorly characterized at high resolution, including many heavier by mass than the precursor benzene. These findings provide direct evidence for a rich architecture of two- and three-dimensional carbon and indicate that benzene growth, particularly the formation of ring-chain molecules, occurs facilely under our experimental conditions. The present analysis also illustrates the utility of microwave spectroscopy as a precision tool for complex mixture analysis, irrespective of whether the rotational spectrum of a product species is known a priori or not. From this large quantity of data, for example, it is possible to determine with confidence the relative abundances of different product masses, but more importantly the relative abundances of different isomers with the same mass. The complementary nature of this type of analysis to traditional mass spectrometry is discussed.

Atmospheric aerosols are large clusters of molecules and particulate matter that profoundly affect the Earth's radiation budget and climate. Gas-phase oxidation of volatile organic compounds is thought to play a key role in nucleation and aerosol growth, but remains poorly understood. One reaction proposed to trigger formation of condensable, low volatility organic compounds is that between Criegee intermediates and carboxylic acids to yield hydroperoxide esters. Here we isolate in high yield the simplest hydroperoxide ester, hydroperoxymethyl formate (HOOCH2OCHO), as a secondary product in the ozonolysis of ethylene, and establish by rotational spectroscopy that this ester adopts a nearly-rigid cyclic structure owing to a strong hydrogen bond between the peroxy hydrogen and carbonyl oxygen. Subsequent detection of this ester in the ozonolysis of propylene and isoprene suggests that terminal alkenes readily undergo specific types of second-order oxidation reactions that have been implicated in the formation of atmospheric aerosols.

The molecular complex between iso-propanol and water has been investigated by Fourier transform microwave spectroscopy. Two distinct rotational spectra have been assigned, corresponding to two different isomers of the adduct. In both cases the water molecule acts as a proton donor to the alcoholic oxygen atom of iso-propanol in its gauche arrangement. The isomer in which the water molecule is oriented along the symmetry plane of the iso-propanol molecule (inner) is more stable than the second isomer, where the water is positioned outside the iso-propanol symmetry plane (outer). The rotational transitions of the inner isomer display a doubling, due to the two equivalent minima related to the internal rotation of the hydroxyl group (concerted with a rearrangement of the water unit). The tunneling splitting has been determined to be 25.16(8) GHz, corresponding to a B 2 barrier of ∼440 cm -1 .

Previous theoretical work on the ethanol-methanol dimer has been inconclusive in predicting the preferred hydrogen bond donor/acceptor configuration. Here, we report the microwave spectrum of the dimer using a chirped pulse Fourier transform microwave spectrometer from 8-18 GHz. In an argon-backed expansion, 50 transitions have been assigned to a trans-ethanol-acceptor/methanol-donor structure that is likely stabilized by a secondary weak C-HO hydrogen bond. A higher energy conformer was observed in a helium-backed expansion and tentatively assigned to a gauche-ethanol-acceptor/methanol-donor structure. No ethanol-donor/methanol-acceptor dimers have been found, suggesting such interactions are energetically disfavored. A preliminary analysis of the A-E splitting due to the internal rotation of the methanol methyl group in the ground state species is also presented. We find evidence of the Ubbelohde effect in the measured A-E splittings of three deuterated isotopologues and the normal species of this conformer.

Life on Earth relies on chiral molecules-that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere. We present the astronomical detection of a chiral molecule, propylene oxide (CH3CHCH2O), in absorption toward the Galactic center. Propylene oxide is detected in the gas phase in a cold, extended molecular shell around the embedded, massive protostellar clusters in the Sagittarius B2 star-forming region. This material is representative of the earliest stage of solar system evolution in which a chiral molecule has been found., (Copyright © 2016, American Association for the Advancement of Science.)

We report the first rotational spectrum of the ground state of the isolated ethanol-water dimer using chirped-pulse Fourier transform microwave spectroscopy between 8-18 GHz. With the aid of isotopic substitutions, and ab initio calculations, we identify the measured conformer as a water-donor/ethanol-acceptor structure. Ethanol is found to be in the gauche conformation, while the monomer distances and orientations likely reflect a cooperation between the strong (O-HO) and weak (C-HO) hydrogen bonds that stabilizes the measured conformer. No other conformers were assigned in an argon expansion, confirming that this is the ground-state structure. This result is consistent with previous vibrationally-resolved Raman and infrared work, but sheds additional light on the structure, due to the specificity of rotational spectroscopy.

We present the design and capabilities of a high-resolution, decade-spanning ASynchronous OPtical Sampling (ASOPS)-based TeraHertz Time-Domain Spectroscopy (THz-TDS) instrument. Our system employs dual mode-locked femtosecond Ti:Sapphire oscillators with repetition rates offset locked at 100 Hz via a Phase-Locked Loop (PLL) operating at the 60th harmonic of the ∼80 MHz oscillator repetition rates. The respective time delays of the individual laser pulses are scanned across a 12.5 ns window in a laboratory scan time of 10 ms, supporting a time delay resolution as fine as 15.6 fs. The repetition rate of the pump oscillator is synchronized to a Rb frequency standard via a PLL operating at the 12th harmonic of the oscillator repetition rate, achieving milliHertz (mHz) stability. We characterize the timing jitter of the system using an air-spaced etalon, an optical cross correlator, and the phase noise spectrum of the PLL. Spectroscopic applications of ASOPS-THz-TDS are demonstrated by measuring water vapor absorption lines from 0.55 to 3.35 THz and acetonitrile absorption lines from 0.13 to 1.39 THz in a short pathlength gas cell. With 70 min of data acquisition, a 50 dB signal-to-noise ratio is achieved. The achieved root-mean-square deviation is 14.6 MHz, with a mean deviation of 11.6 MHz, for the measured water line center frequencies as compared to the JPL molecular spectroscopy database. Further, with the same instrument and data acquisition hardware, we use the ability to control the repetition rate of the pump oscillator to enable THz frequency comb spectroscopy (THz-FCS). Here, a frequency comb with a tooth width of 5 MHz is generated and used to fully resolve the pure rotational spectrum of acetonitrile with Doppler-limited precision. The oscillator repetition rate stability achieved by our PLL lock circuits enables sub-MHz tooth width generation, if desired. This instrument provides unprecedented decade-spanning, tunable resolution, from 80 MHz down to sub-MHz, and heralds a new generation of gas-phase spectroscopic tools in the THz region.

The generation and detection of a decade-spanning terahertz (THz) frequency comb is reported using two Ti:sapphire femtosecond laser oscillators and asynchronous optical sampling THz time-domain spectroscopy. The comb extends from 0.15 to 2.4 THz, with a tooth spacing of 80 MHz, a linewidth of 3.7 kHz, and a fractional precision of 1.8×10^{-9}. With time-domain detection of the comb, we measure three transitions of water vapor at 10 mTorr between 1-2 THz with an average Doppler-limited fractional accuracy of 6.1×10^{-8}. Significant improvements in bandwidth, resolution, and sensitivity are possible with existing technologies.

Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers have become the instrument of choice for acquiring rotational spectra, due to their high sensitivity, fast acquisition rate, and large bandwidth. Here we present the design and capabilities of a recently constructed CP-FTMW spectrometer using direct digital synthesis (DDS) as a new method for chirped pulse generation, through both a suite of extensive microwave characterizations and deep averaging of the 10-14 GHz spectrum of jet-cooled acetone. The use of DDS is more suited for in situ applications of CP-FTMW spectroscopy, as it reduces the size, weight, and power consumption of the chirp generation segment of the spectrometer all by more than an order of magnitude, while matching the performance of traditional designs. The performance of the instrument was further improved by the use of a high speed digitizer with dedicated signal averaging electronics, which facilitates a data acquisition rate of 2.1 kHz.

The creation of successful vascular anastomoses is of primary importance in many surgical fields. Numerous attempts to automate this process have been made. These techniques have slowly gained acceptance, but their use is still limited. This report details feasibility testing of a new prototype stapler that automates the rollover sleeve technique for venous vascular anastomoses. Male and female mongrel dogs (n=7) (25-32 kg) were used. A segment of the right (n=5) or left (n=2) iliac vein was harvested for interposition grafts after the contra lateral side was transected. In each dog, two end-to-end venous anastomoses at the interposition grafts were performed. The standard anastomosis employed continuous mattress sutures. The experimental anastomosis was performed with a new prototype surgical stapler. The stapled anastomosis was proximal and the sutured was distal. In all experiments, it was possible to perform the experimental anastomosis with the stapler. Complications included two small leaks, one due to misfiring of a single pin in one experimental site. These leaks required suture reinforcement. One dog died of hemorrhage due to a slipped suture at the vein harvest site. One vein had thrombus seen at the sutured site although no technical abnormalities at either of the anastomoses could be found. After two weeks, grafts were inspected grossly and histologically. Healing appeared normal. There was a trend for less inflammatory cells infiltrating stapled sites; however, this was not statistically significant. The experiments demonstrate that this device can automate the rollover sleeve technique for venous anastomoses.

In the University of Pittsburgh experience, the most successful setting for human islet allografts is in patients undergoing upper abdominal exenteration with total pancreatectomy and liver transplantation for the indication of malignancy (cluster). In this group of patients 6/11 were insulin-independent for long periods. We report herein the metabolic course or the longest survivor (> 3 years). This patient has been free of exogenous insulin since the third postoperative month and has sustained her body weight without total parenteral nutrition since the 4th postoperative month. The patient has some postprandial hyperglycemia but average capillary glucoses are near-normal to normal as are glycosylated hemoglobin values. The clearance of glucose during the administration of an intravenous glucose load has been well preserved and is currently normal. C-peptide stimulates significantly in response to intravenously injected glucose. The absolute levels of stimulation during the test have declined possibly related to improvements in renal function, decreased immunosuppression or the natural history of cells transplanted into the portal site. The kinetics of the C-peptide response to intravenously injected glucose shows a persistent abnormality of first-phase insulin release and a prolonged second phase release. Basal glucagon levels are low but stimulate to a mixed meal. This patient's results demonstrate long-term function of islet cells from a single donor transplanted into the portal vein using FK506 as an immunosuppressant agent.

Recently, the keratinocyte IL-8/IL-8 receptor (IL-8R) pathway has been implicated in the pathogenesis of psoriasis, and there is evidence that the potent macrolide immune suppressant tacrolimus (formerly FK506) can inhibit this pathway in vitro. In this study, determination of the expression of cytokine mRNAs in lesional skin of patients with active disease by reverse transcriptase polymerase chain reaction revealed transcripts for IL-1 beta, tumour necrosis factor-alpha (TNF-alpha), IL-6, IL-8, IL-8R, IL-10, interferon-gamma (IFN-gamma), IL-2R and transforming growth factor-beta (TGF-beta), but not IL-2 or IL-4. IL-8 was the only cytokine expressed in affected skin of all patients but not in clinically normal skin of healthy subjects. In seven CD4+ T cell clones propagated from the lesional skin of an untreated psoriasis patient, IL-8 was expressed by the skin-derived T lymphocytes and not by feeder cells (irradiated autologous blood lymphocytes); IL-1 beta, IL-2, IL-6 and IL-10 were also expressed by some or all of the T cell clones. IL-8 mRNA was not detected in the skin of any patient after the start of systemic tacrolimus therapy; IL-1 beta, IL-6 and IFN-gamma transcripts were also reduced. By 12 weeks, the mean psoriasis area and severity index (PASI) had decreased from 18.8 to 3.8, a reduction of 80%. In the same post-treatment biopsies, however, message for IL-8R persisted. Estimation of circulating IL-8 levels by enzyme immunoassay showed that all patients with detectable IL-8 before treatment had decreased levels in response to treatment with tacrolimus; reductions in PASI scores were accompanied by decreases in IL-8 levels, that varied both in rate and extent. Partial relapse, which in a minority of patients followed the initial period of remission, and was precipitated by drug dose reduction, was accompanied by an increase in circulating IL-8. These findings add credence to the view that the IL-8/IL-8R autocrine/paracrine pathway may be important in the pathogenesis of psoriasis. They further suggest that interference with IL-8 production and/or that of other key chemokines may be an important mechanism underlying the therapeutic efficacy of tacrolimus, and other agents such as cyclosporin A, with similar molecular actions.