Internal rotation analysis of the microwave and millimeter wave spectra of fluoral (CF3CHO)

The rotational spectrum (4-40 GHz and 50-330 GHz) has been measured and analyzed for trifluoroacetaldehyde, also known as fluoral (CF₃CHO), which is one of the degradation products of the fluorinated contaminants emitted into the atmosphere. The complexity of the spectroscopic analysis of this molecule arises from the strong coupling between the internal rotation motion of CF₃ group and the overall rotation of the molecule. The value obtained for its coupling constant (ρ = 0.91723481(49)) is comparable to the corresponding value of methanol (CH₃OH, ρ = 0.81), which is known for its complex spectrum. A total of 12,322 transitions of the ground, the first and second excited torsional states (ΔE_1υt = 62.0183(13)cm^-1; ΔE_2υt = 120.3315(13)cm^-1) with J ≤ 50 were included in the analysis that was performed employing the rho-axis-method (RAM), and the RAM36 code. A fit within experimental error (root mean square deviation equals to 35 kHz) has been achieved for this dataset using 47 parameters of the RAM torsion-rotation Hamiltonian. In the course of the analysis, it became evident that for such high ρ value, as it is determined for fluoral, a larger than usual torsional basis set at the first diagonalization step of the two-step diagonalization procedure is required for achieving a fit within experimental error.

Emergencia del genotipo Cosmopolitan del virus dengue serotipo 2 (DENV2) en Madre de Dios, Perú, 2019

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The sulphur saga in TMC-1: Discovery of HCSCN and HCSCCH

We report the detection, for the first time in space, of cyano thioformaldehyde (HCSCN) and propynethial (HCSCCH) towards the starless core TMC-1. Cyano thioformaldehyde presents a series of prominent a- and b-type lines, which are the strongest previously unassigned features in our Q-band line survey of TMC-1. Remarkably, HCSCN is four times more abundant than cyano formaldehyde (HCOCN). On the other hand, HCSCCH is five times less abundant than propynal (HCOCCH). Surprisingly, we find an abundance ratio HCSCCH/HCSCN of ∼ 0.25, in contrast with most other ethynyl-cyanide pairs of molecules for which the CCH-bearing species is more abundant than the CN-bearing one. We discuss the formation of these molecules in terms of neutral-neutral reactions of S atoms with CH2CCH and CH2CN radicals as well as of CCH and CN radicals with H2CS. The calculated abundances for the sulphur-bearing species are, however, significantly below the observed values, which points to an underestimation of the abundance of atomic sulphur in the model or to missing formation reactions, such as ion-neutral reactions.

Detection of deuterated methylcyanoacetylene, CH2DC3N, in TMC-1

We report the first detection in space of the single deuterated isotopologue of methylcyanoacetylene, CH2DC3N. A total of fifteen rotational transitions, with J = 8-12 and Ka = 0 and 1, were identified for this species in TMC-1 in the 31.0-50.4 GHz range using the Yebes 40m radio telescope. The observed frequencies were used to derive for the first time the spectroscopic parameters of this deuterated isotopologue. We derive a column density of (8.0 ± 0.4) × 1010 cm-2. The abundance ratio between CH3C3N and CH2DC3N is ∼22. We also theoretically computed the principal spectroscopic constants of 13C isotopologues of CH3C3N and CH3C4H and those of the deuterated isotopologues of CH3C4H for which we could expect a similar degree of deuteration enhancement. However, we have not detected either CH2DC4H nor CH3C4D nor any 13C isotopologue. The different observed deuterium ratios in TMC-1 are reasonably accounted for by a gas phase chemical model where the low temperature conditions favor deuteron transfer through reactions with H2D+.

Cumulene carbenes in TMC-1: Astronomical discovery of l-H2C5 ★

We report the first detection in space of the cumulene carbon chain l-H2C5. A total of eleven rotational transitions, with Jup = 7-10 and Ka = 0 and 1, were detected in TMC-1 in the 31.0-50.4 GHz range using the Yebes 40m radio telescope. We derive a column density of (1.8±0.5)×1010 cm-2. In addition, we report observations of other cumulene carbenes detected previously in TMC-1, to compare their abundances with the newly detected cumulene carbene chain. We find that l-H2C5 is ~4.0 times less abundant than the larger cumulene carbene l-H2C6, while it is ~300 and ~500 times less abundant than the shorter chains l-H2C3 and l-H2C4. We discuss the most likely gas-phase chemical routes to these cumulenes in TMC-1 and stress that chemical kinetics studies able to distinguish between different isomers are needed to shed light on the chemistry of C n H2 isomers with n > 3.

Pure hydrocarbon cycles in TMC-1: Discovery of ethynyl cyclopropenylidene, cyclopentadiene and indene

We report the detection for the first time in space of three new pure hydrocarbon cycles in TMC-1: c-C3HCCH (ethynyl cyclopropenylidene), c-C5H6 (cyclopentadiene) and c-C9H8 (indene). We derive a column density of 3.1 × 1011 cm-2 for the former cycle and similar values, in the range (1-2) × 1013 cm-2, for the two latter molecules. This means that cyclopentadiene and indene, in spite of their large size, are exceptionally abundant, only a factor of five less abundant than the ubiquitous cyclic hydrocarbon c-C3H2. The high abundance found for these two hydrocarbon cycles, together with the high abundance previously found for the propargyl radical (CH2CCH) and other hydrocarbons like vinyl and allenyl acetylene (Agúndez et al. 2021; Cernicharo et al. 2021a,b), start to allow us to quantify the abundant content of hydrocarbon rings in cold dark clouds and to identify the intermediate species that are probably behind the in situ bottom-up synthesis of aromatic cycles in these environments. While c-C3HCCH is most likely formed through the reaction between the radical CCH and c-C3H2, the high observed abundances of cyclopentadiene and indene are difficult to explain through currently proposed chemical mechanisms. Further studies are needed to identify how are five- and six-membered rings formed under the cold conditions of clouds like TMC-1.

O-bearing complex organic molecules at the cyanopolyyne peak of TMC-1: detection of C2H3CHO, C2H3OH, HCOOCH3, and CH3OCH3

We report the detection of the oxygen-bearing complex organic molecules propenal (C2H3CHO), vinyl alcohol (C2H3OH), methyl formate (HCOOCH3), and dimethyl ether (CH3OCH3) toward the cyanopolyyne peak of the starless core TMC-1. These molecules are detected through several emission lines in a deep Q-band line survey of TMC-1 carried out with the Yebes 40m telescope. These observations reveal that the cyanopolyyne peak of TMC-1, which is the prototype of cold dark cloud rich in carbon chains, contains also O-bearing complex organic molecules like HCOOCH3 and CH3OCH3, which have been previously seen in a handful of cold interstellar clouds. In addition, this is the first secure detection of C2H3OH in space and the first time that C2H3CHO and C2H3OH are detected in a cold environment, adding new pieces in the puzzle of complex organic molecules in cold sources. We derive column densities of (2.2 ± 0.3) × 1011 cm™2, (2.5 ± 0.5) × 1012 cm-2, (1.1 ± 0.2) × 1012 cm-2, and (2.5 ± 0.7) × 1012 cm-2 for C2H3CHO, C2H3OH, HCOOCH3, and CH3OCH3, respectively. Interestingly, C2H3OH has an abundance similar to that of its well known isomer acetaldehyde (CH3CHO), with C2H3OH/CH3CHO ~ 1 at the cyanopolyyne peak. We discuss potential formation routes to these molecules and recognize that further experimental, theoretical, and astronomical studies are needed to elucidate the true mechanism of formation of these O-bearing complex organic molecules in cold interstellar sources.

First detection of doubly deuterated methyl acetylene (CHD2CCH and CH2DCCD)★

We report the first detection in space of the two doubly deuterated isotopologues of methyl acetylene. The species CHD2CCH and CH2DCCD were identified in the dense core L483 through nine and eight, respectively, rotational lines in the 72-116 GHz range using the IRAM 30m telescope. The astronomical frequencies observed here were combined with laboratory frequencies from the literature measured in the 29-47 GHz range to derive more accurate spectroscopic parameters for the two isotopologues. We derive beam-averaged column densities of (2.7 ± 0.5) × 1012 cm-2 for CHD2CCH and (2.2 ± 0.4) × 1012 cm-2 for CH2DCCD, which translate to abundance ratios CH3CCH/CHD2CCH = 34 ± 10 and CH3CCH/CH2DCCD = 42 ± 13. The doubly deuterated isotopologues of methyl acetylene are only a few times less abundant than the singly deuterated ones, concretely around 2.4 times less abundant than CH3CCD. The abundances of the different deuterated isotopologues with respect to CH3CCH are reasonably accounted for by a gas-phase chemical model in which deuteration occurs from the precursor ions C3H6D+ and C3H5D+, when the ortho-to-para ratio of molecular hydrogen is sufficiently low. This points to gas-phase chemical reactions, rather than grain-surface processes, as responsible for the formation and deuterium fractionation of CH3CCH in L483. The abundance ratios CH2DCCH/CH3CCD = 3.0 ± 0.9 and CHD2CCH/CH2DCCD = 1.25 ± 0.37 observed in L483 are consistent with the statistically expected values of three and one, respectively, with the slight overabundance of CHD2CCH compared to CH2DCCD being well explained by the chemical model.

TMC-1, the starless core sulfur factory: Discovery of NCS, HCCS, H2CCS, H2CCCS, and C4S and detection of C5S

We report the detection of the sulfur-bearing species NCS, HCCS, H2CCS, H2CCCS, and C4S for the first time in space. These molecules were found towards TMC-1 through the observation of several lines for each species. We also report the detection of C5S for the first time in a cold cloud through the observation of five lines in the 31-50 GHz range. The derived column densities are N(NCS) = (7.8±0.6)×1011 cm-2, N(HCCS) = (6.8±0.6)×1011 cm-2, N(H2CCS) = (7.8±0.8)×1011 cm-2, N(H2CCCS) = (3.7±0.4)×1011 cm-2, N(C4S) = (3.8±0.4)×1010 cm-2, and N(C5S) = (5.0±1.0)×1010 cm-2. The observed abundance ratio between C3S and C4S is 340, that is to say a factor of approximately one hundred larger than the corresponding value for CCS and C3S. The observational results are compared with a state-of-the-art chemical model, which is only partially successful in reproducing the observed abundances. These detections underline the need to improve chemical networks dealing with S-bearing species.

Discovery of CH2CHCCH and detection of HCCN, HC4N, CH3CH2CN, and, tentatively, CH3CH2CCH in TMC-1

We present the discovery in TMC-1 of vinyl acetylene, CH2CHCCH, and the detection, for the first time in a cold dark cloud, of HCCN, HC4N, and CH3CH2CN. A tentative detection of CH3CH2CCH is also reported. The column density of vinyl acetylene is (1.2±0.2)×1013 cm-2, which makes it one of the most abundant closed-shell hydrocarbons detected in TMC-1. Its abundance is only three times lower than that of propylene, CH3CHCH2. The column densities derived for HCCN and HC4N are (4.4±0.4)×1011 cm-2 and (3.7±0.4)×1011 cm-2, respectively. Hence, the HCCN/HC4N abundance ratio is 1.2±0.3. For ethyl cyanide we derive a column density of (1.1 ±0.3)×1011 cm-2. These results are compared with a state-of-the-art chemical model of TMC-1, which is able to account for the observed abundances of these molecules through gas-phase chemical routes.

Discovery of allenyl acetylene, H2CCCHCCH, in TMC-1. A study of the isomers of C5H4

We present the discovery in TMC-1 of allenyl acetylene, H2CCCHCCH, through the observation of nineteen lines with a signal-to-noise ratio ~4-15. For this species, we derived a rotational temperature of 7±1K and a column density of 1.2±0.2×1013 cm-2. The other well known isomer of this molecule, methyl diacetylene (CH3C4H), has also been observed and we derived a similar rotational temperature, Tr=7.0±0.3 K, and a column density for its two states (A and E) of 6.5±0.3×1012 cm-2. Hence, allenyl acetylene and methyl diacetylene have a similar abundance. Remarkably, their abundances are close to that of vinyl acetylene (CH2CHCCH). We also searched for the other isomer of C5H4, HCCCH2CCH (1.4-Pentadiyne), but only a3σ upper limit of 2.5×1012 cm-2 to the column density can be established. These results have been compared to state-of-the-art chemical models for TMC-1, indicating the important role of these hydrocarbons in its chemistry. The rotational parameters of allenyl acetylene have been improved by fitting the existing laboratory data together with the frequencies of the transitions observed in TMC-1.

Discovery of the propargyl radical (CH2CCH) in TMC-1: one of the most abundant radicals ever found and a key species for cyclization to benzene in cold dark clouds

We present the first identification in interstellar space of the propargyl radical (CH2CCH). This species was observed in the cold dark cloud TMC-1 using the Yebes 40m telescope. The six strongest hyperfine components of the 20,2-10,1 rotational transition, lying at 37.46 GHz, were detected with signal-to-noise ratios in the range 4.6-12.3 σ. We derive a column density of 8.7 × 1013 cm-2 for CH2CCH, which translates to a fractional abundance relative to H2 of 8.7 × 10-9. This radical has a similar abundance to methyl acetylene, with an abundance ratio CH2CCH/CH3CCH close to one. The propargyl radical is thus one of the most abundant radicals detected in TMC-1, and it is probably the most abundant organic radical with a certain chemical complexity ever found in a cold dark cloud. We constructed a gas-phase chemical model and find calculated abundances that agree with, or fall two orders of magnitude below, the observed value depending on the poorly constrained low-temperature reactivity of CH2CCH with neutral atoms. According to the chemical model, the propargyl radical is essentially formed by the C + C2H4 reaction and by the dissociative recombination of C3Hn + ions with n = 4-6. The propargyl radical is believed to control the synthesis of the first aromatic ring in combustion processes, and it probably plays a key role in the synthesis of large organic molecules and cyclization processes to benzene in cold dark clouds.

Space and laboratory discovery of HC3 . ASTRONOMY AND ASTROPHYSICS 2021;646:L3. [PMID: 33824540 PMCID: PMC7610522 DOI: 10.1051/0004-6361/202040013]

We report the detection in TMC-1 of the protonated form of C3S. The discovery of the cation HC3S+ was carried through the observation of four harmonically related lines in the Q band using the Yebes 40m radiotelescope, and is supported by accurate ab initio calculations and laboratory measurements of its rotational spectrum. We derive a column density N(HC3S+) = (2.0 ± 0.5) × 1011 cm-2, which translates to an abundance ratio C3S/HC3S+ of 65 ± 20. This ratio is comparable to the CS/HCS+ ratio (35 ± 8) and is a factor of about ten larger than the C3O/HC3O+ ratio previously found in the same source. However, the abundance ratio HC3O+/HC3S+ is 1.0 ± 0.5, while C3O/C3S is just ~ 0.11. We also searched for protonated C2S in TMC-1, based on ab initio calculations of its spectroscopic parameters, and derive a 3σ upper limit of N(HC2S+)≤ 9×1011 cm-2 and a C2S/HC2S+ ≥ 60. The observational results are compared with a state-of-the-art gas-phase chemical model and conclude that HC3S+ is mostly formed through several pathways: proton transfer to C3S, reaction of S+ with c-C3H2, and reaction between neutral atomic sulfur and the ion C3H+ 3.

Discovery of the acetyl cation, CH3CO+, in space and in the laboratory

Using the Yebes 40m and IRAM 30m radiotelescopes, we detected two series of harmonically related lines in space that can be fitted to a symmetric rotor. The lines have been seen towards the cold dense cores TMC-1, L483, L1527, and L1544. High level of theory ab initio calculations indicate that the best possible candidate is the acetyl cation, CH3CO+, which is the most stable product resulting from the protonation of ketene. We have produced this species in the laboratory and observed its rotational transitions Ju = 10 up to Ju = 27. Hence, we report the discovery of CH3CO+ in space based on our observations, theoretical calculations, and laboratory experiments. The derived rotational and distortion constants allow us to predict the spectrum of CH3CO+ with high accuracy up to 500 GHz. We derive an abundance ratio N(H2CCO)/N(CH3CO+)~44. The high abundance of the protonated form of H2CCO is due to the high proton affinity of the neutral species. The other isomer, H2CCOH+, is found to be 178.9 kJ mol-1 above CH3CO+. The observed intensity ratio between the K=0 and K=1 lines, ~2.2, strongly suggests that the A and E symmetry states have suffered interconversion processes due to collisions with H and/or H2, or during their formation through the reaction of H 3 + with H2CCO.

Comprehensive rotational study and astronomical search for cyclopropanecarboxaldehyde

CONTEXT

At least a dozen molecules with a formyl group (HCO) have been observed to date in the interstellar medium (ISM), suggesting that other such species exist and remain to be discovered. However, there is still a lack of high-resolution spectroscopic data for simple molecular species of this type that could provide a basis for their detection.

AIMS

Cyclopropanecarboxaldehyde, c-C3H5CHO, is a small molecule containing a formyl group and is therefore an interesting candidate for astrophysical detection. The rotational spectrum of cyclopropanecarboxaldehyde has been observed before, but its experimental rotational parameters are not precise enough to allow its detection in the millimetre-wave domain.

METHODS

We measured the rotational spectrum of cyclopropanecarboxaldehyde in the frequency ranges 31.5-50 GHz and 72-116.5 GHz using the GACELA (GAS CEll for Laboratory Astrophysics) broadband high-resolution rotational spectrometer constructed at the Yebes Observatory. The spectroscopic study was supported by high-level theoretical calculations which were used in the identification of the vibrational excited states of cyclopropanecarboxaldehyde.

RESULTS

Our analysis of the rotational spectrum of cyclopropanecarboxaldehyde allowed us to obtain accurate rotational parameters for the ground state of both cis and trans isomers, which were used to derive sufficiently reliable predictions up to 300 GHz. In addition to the ground states, we identified 12 and 6 vibrationally excited states for the trans and cis isomers, respectively, including fundamental modes, multiple excitation quanta, and combination states. We find that the gas phase concentration of the trans isomer is almost 1.2 times larger than that of the cis one. These new experimental rotational parameters were employed to search for cyclopropanecarboxaldehyde in the warm molecular clouds Orion KL and Sgr B2(N) using the spectral surveys captured by ALMA (Orion) and IRAM 30 m (Sgr) at 1 mm and 3 mm, respectively.

Tentative detection of HC5NH+ in TMC-1

Using the Yebes 40m radio telescope, we report the detection of a series of seven lines harmonically related with a rotational constant B 0=1295.81581 ± 0.00026 MHz and a distortion constant D 0 = 27.3 ± 0.5 Hz towards the cold dense cloud TMC-1. Ab initio calculations indicate that the best possible candidates are the cations HC5NH+ and NC4NH+. From a comparison between calculated and observed rotational constants and other arguments based on proton affinities and dipole moments, we conclude that the best candidate for a carrier of the observed lines is the protonated cyanodiacetylene cation, HC5NH+. The HC5N/HC5NH+ ratio derived in TMC-1 is 240, which is very similar to the HC3N/HC3NH+ ratio. Results are discussed in the framework of a chemical model for protonated molecules in cold dense clouds.

Discovery of HC4NC in TMC-1: A study of the isomers of HC3N, HC5N, and HC7N

We present a study of the isocyano isomers of the cyanopolyynes HC₃N, HC₅N, and HC₇N in TMC-1 and IRC+10216 carried out with the Yebes 40m radio telescope. This study has enabled us to report the detection, for the first time in space, of HCCCCNC in TMC-1 and to give upper limits for HC₆NC in the same source. In addition, the deuterated isotopologues of HCCNC and HNCCC were detected, along with all ¹³C substitutions of HCCNC, also for the first time in space. The abundance ratios of HC₃N and HC₅N, with their isomers, are very different in TMC-1 and IRC+10216, namely, N(HC₅N)/N(HC₄NC) is ~300 and ≥2100, respectively. We discuss the chemistry of the metastable isomers of cyanopolyynes in terms of the most likely formation pathways and by comparing observational abundance ratios between different sources.

Discovery of HC3O+ in space: The chemistry of O-bearing species in TMC-1

Using the Yebes 40m and IRAM 30m radio telescopes, we detected a series of harmonically related lines with a rotational constant B 0=4460.590±0.001 MHz and a distortion constant D 0=0.511 ±0.005 kHz towards the cold dense core TMC-1. High-level-of-theory ab initio calculations indicate that the best possible candidate is protonated tricarbon monoxide, HC3O+. We have succeeded in producing this species in the laboratory and observed its J u -J l = 2-1 and 3-2 rotational transitions. Hence, we report the discovery of HC3O+ in space based on our observations, theoretical calculations, and laboratory experiments. We derive an abundance ratio N(C3O)/N(HC3O+)~7. The high abundance of the protonated form of C3O is due to the high proton affinity of the neutral species. The chemistry of O-bearing species is modelled, and predictions are compared to the derived abundances from our data for the most prominent O-bearing species in TMC-1.

Interstellar nitrile anions: Detection of C3N- and C5N- in TMC-1. ASTRONOMY AND ASTROPHYSICS 2020;641:L9. [PMID: 33173234 PMCID: PMC7116340 DOI: 10.1051/0004-6361/202039231]

We report on the first detection of C3N- and C5N- towards the cold dark core TMC-1 in the Taurus region, using the Yebes 40 m telescope. The observed C3N/C3N- and C5N/C5N- abundance ratios are ~140 and ~2, respectively; that is similar to those found in the circumstellar envelope of the carbon-rich star IRC +10216. Although the formation mechanisms for the neutrals are different in interstellar (ion-neutral reactions) and circumstellar clouds (photodissociation and radical-neutral reactions), the similarity of the C3N/C3N- and C5N/C5N- abundance ratios strongly suggests a common chemical path for the formation of these anions in interstellar and circumstellar clouds. We discuss the role of radiative electronic attachment, reactions between N atoms and carbon chain anions C n -, and that of H- reactions with HC3N and HC5N as possible routes to form C n N-. The detection of C5N- in TMC-1 gives strong support for assigning to this anion the lines found in IRC +10216, as it excludes the possibility of a metal-bearing species, or a vibrationally excited state. New sets of rotational parameters have been derived from the observed frequencies in TMC-1 and IRC +10216 for C5N- and the neutral radical C5N.

Decrease in the prevalence of hepatitis B and D virus infections in an endemic area in Peru 23 years after the introduction of the first pilot vaccination program against hepatitis B

In 1991, Peru launched the first vaccination program against hepatitis B in children aged under 5 years in the hyperendemic [hepatitis B virus (HBV) and hepatitis D virus (HDV)] province of Abancay. We conducted a cross-sectional study to determine the prevalence of HBV and HDV infections, 23 years after the launch of the vaccination program, as well as the post-vaccine response against hepatitis B in terms of prevalence of hepatitis B surface antibody (anti-HBs ≥10 mUI/ml). Among 3165 participants aged from 0 to 94 years, the prevalence rates of hepatitis B surface antigen (HBsAg), and hepatitis B core antibody (total anti-HBc) were 1.2% [95% confidence interval (CI) 0.85–1.64%], and 41.67% (95% CI 39.95–43.41%), respectively. The prevalence rate of anti-HBs at protective levels (≥10 mUI/ml) in individuals who HBsAg and anti-HBc negative was 66.36% (95% CI 64.15–68.51%). The prevalence rate of HBsAg in children aged <15 years was nil, and among adult HBsAg carriers, the prevalence of hepatitis D antibody (anti-HDV) was 5.26% (2/38; 95% CI 0.64–17.74). These findings showed that HBV prevalence has changed from high to low endemicity, 23 years following implementation of the vaccination program against hepatitis B, and HDV infection was not detected in those aged <30 years.

Detection of vibrationally excited HC7N and HC9N in IRC+10216 ⋆

Observations of IRC +10216 with the Yebes 40m telescope between 31 and 50 GHz have revealed more than 150 unidentified lines. Some of them can be grouped into a new series of 26 doublets, harmonically related with integer quantum numbers ranging from J up=54 to 80. The separation of the doublets increases systematically with J, i.e., as expected for a linear species in one of its bending modes. The rotational parameters resulting from the fit to these data are B = 290.8844 ± 0.0004 MHz, D = 0.88 ± 0.04 Hz, q = 0.1463 ± 0.0001 MHz. The rotational constant is very close to that of the ground state of HC9N. Ab initio calculations show an excellent agreement between these parameters and those predicted for the lowest energy vibrationally excited state, ν 19=1, of HC9N. This is the first detection, and complete characterization in space, of vibrationally excited HC9N. An energy of 41.5 cm-1 is estimated for the ν 19 state. In addition, 17 doublets of HC7N in the ν 15=1 state, for which laboratory spectroscopy is available, have been detected for the first time in IRC+10216. Several doublets of HC5N in its ν 11=1 state have been also observed. The column density ratio between the ground and the lowest excited vibrational states are ≈127, 9.5, and 1.5 for HC5N, HC7N, and HC9N, respectively. We find that these lowest-lying vibrational states are most probably populated via infrared pumping to vibrationally excited states lying at ≈600 cm-1. The lowest vibrationally excited states thus need to be taken into account to precisely determine absolute abundances and abundanceratios for long carbon chains. The abundance ratios N(HC5N)/N(HC7N) and N(HC7N)/N(HC9N) are 2.4 and 7.7 respectively.

The millimeter-wave spectrum and astronomical search for ethyl methyl sulfide

CONTEXT

Sulfur-containing molecules constitute only 8% of the molecules observed in the interstellar medium (ISM), in spite of the fact that sulfur has been shown to be an abundant element in the ISM. In order to understand the chemical behavior of the ISM and specific cases like the missing sulfur reservoir, a detailed chemical molecular composition in the ISM must be mapped out.

AIMS

Our goal is to investigate the rotational spectrum of ethyl methyl sulfide, CH₃CH₂SCH₃, which ms to be a potential candidate for observation in the ISM since the simpler analogs, CH₃SH and CH₃CH₂SH, have already been detected. Rotational spectrum of ethyl methyl sulfide has been observed before, but its experimental rotational parameters are not precise enough to allow its detection in the ISM.

METHODS

The rotational spectrum of ethyl methyl sulfide in the frequency range 72-116.5 GHz was measured using a broadband millimeter-wave spectrometer based on radio astronomy receivers with fast Fourier transform backends. The spectral searches and identification of the vibrational excited states of ethyl methyl sulfide was supported by high-level ab initio calculations on the harmonic and anharmonic force fields.

RESULTS

The rotational spectra for the trans and gauche conformers of ethyl methyl sulfide was analyzed, and a total of 172 and 259 rotational transitions were observed for each one, respectively. The observation of A - E internal rotation splittings allowed the experimental determination of the V ₃ hindered internal rotation barrier height for both trans and gauche species. In addition, the vibrational excited states, resulting from the lowest frequency vibrational mode ν ₃₀ were identified for both conformers. The new experimental rotational parameters were employed to search for ethyl methyl sulfide in the warm and cold molecular clouds Orion KL, Sgr B2(N), B1-b and TMC-1, using the spectral surveys captured by IRAM 30 m at 3 mm and 2 mm.

Rotational spectroscopy and astronomical search for glutaronitrile★

CONTEXT

Nitriles constitute almost 15% of the molecules observed in the interstellar medium (ISM), surprisingly only two dinitriles have been detected in the ISM so far. The lack of astronomical detections for dinitriles may be partly explained by the absence of laboratory rotational spectroscopic data.

AIMS

Our goal is to investigate the rotational spectrum of glutaronitrile, N≡C-CH2-CH2-CH2-C≡N, in order to allow its possible detection in the ISM.

METHODS

The rotational spectrum of glutaronitrile was measured using two different experimental setups. A Fourier transform microwave spectrometer was employed to observe the supersonic jet rotational spectrum of glutaronitrile between 6 and 20 GHz. In addition, the mmW spectrum was observed in the frequency range 72-116.5 GHz using a broadband millimetre-wave spectrometer based on radio astronomy receivers with fast Fourier transform backends. The spectral searches were supported by high-level ab initio calculations.

RESULTS

A total of 111 rotational transitions with maximum values of J and Ka quantum numbers 54 and 18, respectively, were measured for the gg conformer of glutaronitrile. The analysis allowed us to accurately determine the rotational, nuclear quadrupole coupling, quartic and sextic centrifugal distortion constants. These rotational parameters were employed to search for glutaronitrile in the cold and warm molecular clouds Orion KL, Sgr B2(N), B1-b and TMC-1, using the spectral surveys captured by IRAM 30m at 3mm. Glutaronitrile was not detected, and the upper limits' column densities were derived. Those are a factor of 1.5 and 5 lower than those obtained for the total column densities of the analogous succinonitrile in Orion KL and Sgr B2, respectively.

Discovery of two new magnesium-bearing species in IRC+10216: MgC3N and MgC4H

We report on the detection of two series of harmonically related doublets in IRC +10216. From the observed frequencies, the rotational constant of the first series is B = 1380.888 MHz and that of the second series is B = 1381.512 MHz. The two series correspond to two species with a 2Σ electronic ground state. After considering all possible candidates, and based on quantum chemical calculations, the first series is assigned to MgC3N and the second to MgC4H. For the latter species, optical spectroscopy measurements support its identification. Unlike diatomic metal-containing molecules, the line profiles of the two new molecules indicate that they are formed in the outer layers of the envelope, as occurs for MgNC and other polyatomic metal-cyanides. We also confirm the detection of MgCCH that was previously reported from the observation of two doublets. The relative abundance of MgC3N with respect to MgNC is close to one while that of MgC4H relative to MgCCH is about ten. The synthesis of these magnesium cyanides and acetylides in IRC +10216 can be explained in terms of a two-step process initiated by the radiative association of Mg+ with large cyanopolyynes and polyynes followed by the dissociative recombination of the ionic complexes.

The millimeter-wave spectrum and astronomical search of succinonitrile and its vibrational excited states ★

CONTEXT

Dinitriles with a saturated hydrocarbon skeleton and a -C≡N group at each end can have large electric dipole moments. Their formation can be related to highly reactive radicals such as CH2CN, C2N or CN. Thus, these saturated dinitriles are potential candidates to be observed in the ISM.

AIMS

Our goal is the investigation of the rotational spectrum of one of the simplest dinitriles N≡C-CH2-CH2-C≡N, succinonitrile, whose actual rotational parameters are not precise enough to allow its detection in the ISM. In addition, the rotational spectra for its vibrational exicted states will be analyzed.

METHODS

The rotational spectra of succinonitrile was measured in the frequency range 72-116.5 GHz using a new broadband millimeter-wave spectrometer based on radio astronomy receivers with Fast Fourier Transform backends. The identification of the vibrational excited states of succinonitrile was supported by high-level ab initio calculations on the harmonic and anharmonic force fields.

RESULTS

A total of 459 rotational transitions with maximum values of J and Ka quantum numbers 70 and 14, respectively, were measured for the ground vibrational state of succinonitrile. The analysis allowed us to accurately determine the rotational, quartic and sextic centrifugal distortion constants. Up to eleven vibrational excited states, resulting from the four lowest frequency vibrational modes ν 13, ν 12, ν 24 and ν 23 were identified. In addition to the four fundamental modes, we observed overtones together with some combination states. The rotational parameters for the ground state were employed to unsuccessfully search for succinonitrile in the cold and warm molecular clouds Orion KL, Sgr B2(N), B1-b and TMC-1, using the spectral surveys captured by IRAM 30m at 3mm and the Yebes 40m at 1.3cm and 7mm.

CONCLUSIONS

Discovery of the first Ca-bearing molecule in space: CaNC

We report on the detection of calcium isocyanide, CaNC, in the carbon-rich evolved star IRC+10216. We derived a column density for this species of (2±0.5)×1011 cm-2. Based on the observed line profiles and the modelling of its emission through the envelope, the molecule has to be produced in the intermediate and outer layers of the circumstellar envelope where other metal-isocyanides have previously been found in this source. The abundance ratio of CaNC relative to MgNC and FeCN is ≃1/60 and ≃1, respectively. We searched for the species CaF, CaCl, CaC, CaCCH, and CaCH3 for which accurate frequency predictions are available. Only upper limits have been obtained for these molecules.

Cobertura de inmunización contra el virus de la hepatitis B en hijos nacidos de madres portadoras de la infección. Huanta, Ayacucho, 2014-2018

Introducción. En el marco del plan de eliminación de la infección por virus de la hepatitis B (HBV) es necesario conocer la cobertura de inmunización en los hijos de madres portadoras. Objetivo. Determinar el nivel de cobertura de inmunización en los hijos nacidos de madres portadoras de la infección por HBV en el Hospital de Huanta, Ayacucho, entre los años 2014 a 2018. Métodos. Se realizó un estudio observacional descriptivo. La población incluyó a los hijos nacidos de madres portadoras de la infección por HBV. Se utilizaron fuentes de información secundaria de registro de inmunización contra HBV. Resultados. Se registraron 90 madres portadoras de la infección por HBV cuyos hijos nacieron en el lugar de estudio. La cobertura total de inmunización contra HBV fue 64,47%, la cobertura de la dosis de nacimiento de la vacuna fue 100% y la cobertura de aplicación de la inmunoglobulina antihepaitis B de 77,78%. Conclusiones. La cobertura total de inmunización contra HBV se encuentra por debajo de lo esperado según las recomendaciones de la OMS.

Broad band high resolution rotational spectroscopy for Laboratory Astrophysics

We present a new experimental setup devoted to the study of gas phase molecules and processes using broad band high spectral resolution rotational spectroscopy. A reactor chamber has been equipped with radio receivers similar to those used by radio astronomers to search for molecular emission in space. The whole Q (31.5-50 GHz) and W bands (72-116.5 GHz) are available for rotational spectroscopy observations. The receivers are equipped with 16×2.5 GHz Fast Fourier Transform spectrometers with a spectral resolution of 38.14 kHz allowing the simultaneous observation of the complete Q band and one third of the W band. The whole W band can be observed in three settings in which the Q band is always observed. Species such as CH3CN, OCS, and SO2 are detected, together with many of their isotopologues and vibrationally excited states, in very short observing times. The system permits automatic overnight observations and integration times as long as 2.4×105 seconds have been reached. The chamber is equipped with a radiofrequency source to produce cold plasmas and with four ultraviolet lamps to study photochemical processes. Plasmas of CH4, N2, CH3CN, NH3, O2, and H2, among other species, have been generated and the molecular products easily identified by their rotational spectrum, and mass spectrometry and optical spectroscopy. Finally, the rotational spectrum of the lowest energy conformer of CH3CH2NHCHO (N-Ethylformamide), a molecule previously characterized in microwave rotational spectroscopy, has been measured up to 116.5 GHz allowing the accurate determination of its rotational and distortion constants and its search in space.

Elucidating the multiple structures of pipecolic acid by rotational spectroscopy

The complex conformational space of the non-proteinogenic cyclic amino acid pipecolic acid has been explored in the gas phase for the first time. Solid pipecolic acid samples were vaporized by laser ablation and expanded in a supersonic jet where the rotational spectral signatures owing to nine different conformers were observed by Fourier transform microwave spectroscopy. All species were identified by comparison of the experimental rotational and nuclear quadrupole coupling constants with those predicted theoretically. Observation of type-III conformers, leading to a difference when compared against the conformational behavior of the analog amino acid proline, has been interpreted by an increment in steric hindrance when increasing the number of carbons present in the ring.

The last link of the x-aminobutyric acid series: the five conformers of β-aminobutyric acid

Structural characterization of β-aminobutyric acid by rotational spectroscopy.

The role of amino acid side chains in stabilizing dipeptides: the laser ablation Fourier transform microwave spectrum of Ac-Val-NH2

The steric effects imposed by the isopropyl group of valine in the conformational stabilization of the capped dipeptide N-acetyl-l-valinamide (Ac-Val-NH₂) have been studied by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy.

High-Resolution Rotational Spectrum, Dunham Coefficients, and Potential Energy Function of NaCl

We report laboratory spectroscopy for the first time of the J = 1-0 and J = 2-1 lines of Na35Cl and Na37Cl in several vibrational states. The hyperfine structure has been resolved in both transitions for all vibrational levels, which permit us to predict with high accuracy the hyperfine splitting of the rotational transitions of the two isotopologues at higher frequencies. The new data have been merged with all previous works at microwave, millimeter, and infrared wavelengths and fitted to a series of mass-independent Dunham parameters and to a potential energy function. The obtained parameters have been used to compute a new dipole moment function, from which the dipole moment for infrared transitions up to Δv = 8 has been derived. Frequency and intensity predictions are provided for all rovibrational transitions up to J = 150 and v = 8, from which the ALMA data of evolved stars can be modeled and interpreted.

Accelerating to Zero: Strategies to Eliminate Malaria in the Peruvian Amazon

AbstractIn February 2014, the Malaria Elimination Working Group, in partnership with the Peruvian Ministry of Health (MoH), hosted its first international conference on malaria elimination in Iquitos, Peru. The 2-day meeting gathered 85 malaria experts, including 18 international panelists, 23 stakeholders from different malaria-endemic regions of Peru, and 11 MoH authorities. The main outcome was consensus that implementing a malaria elimination project in the Amazon region is achievable, but would require: 1) a comprehensive strategic plan, 2) the altering of current programmatic guidelines from control toward elimination by including symptomatic as well as asymptomatic individuals for antimalarial therapy and transmission-blocking interventions, and 3) the prioritization of community-based active case detection with proper rapid diagnostic tests to interrupt transmission. Elimination efforts must involve key stakeholders and experts at every level of government and include integrated research activities to evaluate, implement, and tailor sustainable interventions appropriate to the region.

Hints of a rotating spiral structure in the innermost regions around IRC +10216

The Atacama Large Millimeter/submillimeter Array (ALMA) is allowing us to study the innermost regions of the circumstellar envelopes of evolved stars with un-precedented precision and sensitivity. Key processes in the ejection of matter and dust from these objects occur in their inner zones. In this work, we present sub-arcsecond interferometric maps of transitions of metal-bearing molecules towards the prototypical C-rich evolved star IRC +10216. While Al-bearing molecules seem to be present as a roughly spherical shell, the molecular emission from the salts NaCl and KCl presents an elongation in the inner regions, with a central minimum. In order to accurately analyze the emission from the NaCl rotational lines, we present new calculations of the collisional rates for this molecule based on new spectroscopic constants. The most plausible interpretation for the spatial distribution of the salts is a spiral with a NaCl mass of 0.08M☉. Alternatively, a torus of gas and dust would result in similar structures as those observed. From the torus scenario we derive a mass of ~ 1.1 × 10-4M☉. In both cases, the spiral and the torus, the NaCl structure presents an inner minimum of 27 AU. In the case of the torus, the outer radius is 73 AU. The kinematics of both the spiral and the torus suggests that they are slowly expanding and rotating. Alternative explanations for the presence of the elongation are explored. The presence of these features only in KCl and NaCl might be a result of their comparatively high dipole moment with respect to the Al-bearing species.

Molecular Investigation into a Malaria Outbreak in Cusco, Peru: Plasmodium falciparum BV1 Lineage is Linked to a Second Outbreak in Recent Times

In November 2013, a Plasmodium falciparum malaria outbreak of 11 cases occurred in Cusco, southern Peru, where falciparum malaria had not been reported since 1946. Although initial microscopic diagnosis reported only Plasmodium vivax infection in each of the specimens, subsequent examination by the national reference laboratory confirmed P. falciparum infection in all samples. Molecular typing of four available isolates revealed identity as the B-variant (BV1) strain that was responsible for a malaria outbreak in Tumbes, northern Peru, between 2010 and 2012. The P. falciparum BV1 strain is multidrug resistant, can escape detection by PfHRP2-based rapid diagnostic tests, and has contributed to two malaria outbreaks in Peru. This investigation highlights the importance of accurate species diagnosis given the potential for P. falciparum to be reintroduced to regions where it may have been absent. Similar molecular epidemiological investigations can track the probable source(s) of outbreak parasite strains for malaria surveillance and control purposes.

Conformers of β-aminoisobutyric acid probed by jet-cooled microwave and matrix isolation infrared spectroscopic techniques

β-aminoisobutyric acid (BAIBA) has been studied in isolation conditions: in the gas phase and trapped into a cryogenic N2 matrix. A solid sample of the compound was vaporized by laser ablation and investigated through their rotational spectra in a supersonic expansion using two different spectroscopic techniques: broadband chirped pulse Fourier transform microwave spectroscopy and conventional molecular beam Fourier transform microwave spectroscopy. Four conformers with structures of two types could be successfully identified by comparison of the experimental rotational and (14)N nuclear quadruple coupling constants with those predicted theoretically: type A, bearing an OH⋯N intramolecular hydrogen bond and its carboxylic group in the trans geometry (H-O-C=O dihedral ∼180°), and type B, having an NH⋯O bond and the cis arrangement of the carboxylic group. These two types of conformers could also be trapped from the gas phase into a cryogenic N2 matrix and probed by Fourier transform infrared (IR) spectroscopy. In situ irradiation of BAIBA isolated in N2 matrix of type B conformers using near-IR radiation tuned at the frequency of the O-H stretching 1st overtone (∼6930 cm(-1)) of these forms allowed to selectively convert them into type A conformers and into a new type of conformers of higher energy (type D) bearing an NH⋯O=C bond and a O-H "free" trans carboxylic group.

Efficacy of three different regimens of primaquine for the prevention of relapses of Plasmodium vivax malaria in the Amazon Basin of Peru

We evaluated the efficacy of three primaquine (PQ) regimes to prevent relapses with Plasmodium vivax through an open-label randomized trial in Loreto, Peru. Vivax monoinfections were treated with chloroquine for 3 days and PQ in three different regimes: 0.5 mg/kg per day for 5 days (150 mg total), 0.5 mg/kg per day for 7 days (210 mg total), or 0.25 mg/kg per day for 14 days (210 mg total). Biweekly fever assessments and bimonthly thick smears were taken for 210 days. Recurrences after 35 days were considered relapses. One hundred eighty cases were enrolled in each group; 90% of cases completed follow-up. There were no group-related differences in age, sex, or parasitemia. Relapse rates were similar in the 7- and 14-day regimes (16/156 = 10.3% and 22/162 = 13.6%, P = 0.361) and higher in the 5-day group (48/169 = 28.4%, P < 0.001 and P = 0.001, respectively). The 7-day PQ regimen used in Peru is as efficacious as the recommended 14-day regimen and superior to 5 treatment days.

Genetic variation and recurrent parasitaemia in Peruvian Plasmodium vivax populations

Background

Plasmodium vivax is a predominant species of malaria in parts of South America and there is increasing resistance to drugs to treat infections by P. vivax. The existence of latent hypnozoites further complicates the ability to classify recurrent infections as treatment failures due to relapse, recrudescence of hyponozoites or re-infections. Antigen loci are putatively under natural selection and may not be an optimal molecular marker to define parasite haplotypes in paired samples. Putatively neutral microsatellite loci, however, offer an assessment of neutral haplotypes. The objective here was to assess the utility of neutral microsatellite loci to reconcile cases of recurrent parasitaemia in Amazonian P. vivax populations in Peru.

Methods

Patient blood samples were collected from three locations in or around Iquitos in the Peruvian Amazon. Five putatively neutral microsatellite loci were characterized from 445 samples to ascertain the within and amongst population variation. A total of 30 day 0 and day of recurrent parasitaemia samples were characterized at microsatellite loci and five polymorphic antigen loci for haplotype classification.

Results

The genetic diversity at microsatellite loci was consistent with neutral levels of variation measured in other South American P. vivax populations. Results between antigen and microsatellite loci for the 30 day 0 and day of recurrent parasitaemia samples were the same for 80% of the pairs. The majority of non-concordant results were the result of differing alleles at microsatellite loci. This analysis estimates that 90% of the paired samples with the same microsatellite haplotype are unlikely to be due to a new infection.

Conclusions

A population-level approach was used to yield a better estimate of the probability of a new infection versus relapse or recrudescence of homologous hypnozoites; hypnozoite activation was common for this cohort. Population studies are critical with the evaluation of genetic markers to assess P. vivax biology and epidemiology. The additional demonstration of microsatellite loci as neutral markers capable of distinguishing the origin of the recurrent parasites (new infection or originating from the patient) lends support to their use in assessment of treatment outcomes.

Being unaware of being HIV-infected is associated with alcohol use disorders and high-risk sexual behaviors among men who have sex with men in Peru

This study compared the correlates of HIV risk among men who have sex with men (MSM) with newly diagnosed versus previously known HIV infection among 5,148 MSM recruited using modified snowball sampling in 5 Peruvian cities. Participants, if age ≥18 years and reporting sex with a male in the previous 12 months, underwent standardized computer-assisted risk assessments and HIV and syphilis testing. Overall, 420 (8.2 %) participants tested HIV seropositive, most of whom (89.8 %) were unaware of their HIV status. Compared to those who knew themselves to be HIV-infected, multivariate logistic regression demonstrated that unprotected anal intercourse at last encounter [AOR = 2.84 (95 % CI 1.09-7.40)] and having an alcohol use disorder (AUD) [AOR = 2.14 (95 % CI 1.01-5.54)] were independently associated with a newly diagnosed HIV infection. Being unaware of being HIV-infected was associated with high-risk sexual behaviors and AUDs, both of which are amenable to behavioral and medication-assisted therapy interventions.

El timerosal y las enfermedades del neurodesarrollo infantil: Comentarios y respuestas

Quiero comentarle sobre las versiones periodísticas sobre el artículo del Dr. Maya publicado en la Revista de la Facultad, sobre el timerosal y vacunas. Desde el año 1991, venimos trabajando con vacunas en recién nacidos y menores de 5 años, sin haber documentado los efectos que mencionan en dicho tema de debate. Por otro lado, hay estudios serios, en países en donde se retiró las vacunas con timerosal y los casos de autismo siguen en igual o en mayor número. Siendo este tema controversial, la difusión a través de los medios de aspectos no comprobados perjudica la aceptación de las vacunas en la población. Conociendo las miles de vidas que salvan las vacunas y el ahorro en el sufrimiento y la economía de las familias así como del país, considero no muy serio que los médicos, que debiéramos mas bien mejorar la protección de la salud, estemos sembrando la desconfianza en las vacunas, atribuyéndoles efectos no comprobados.

Genetic characterization of atypical Mansonella (Mansonella) ozzardi microfilariae in human blood samples from northeastern Peru

DNA sequence comparisons are useful for characterizing proposed new parasite species or strains. Microfilariae with an atypical arrangement of nuclei behind the cephalic space have been recently described in human blood samples from the Amazon region of Peru. Three blood specimens containing atypical microfilariae were genetically characterized using three DNA markers (5S ribosomal DNA, 12S ribosomal DNA, and cytochrome oxidase I). All atypical microfilariae were clustered into the Mansonella group and indistinguishable from M. ozzardi based on these DNA markers.

Association of neurexin 3 polymorphisms with smoking behavior

The Neurexin 3 gene (NRXN3) has been associated with dependence on various addictive substances, as well as with the degree of smoking in schizophrenic patients and impulsivity among tobacco abusers. To further evaluate the role of NRXN3 in nicotine addiction, we analyzed single nucleotide polymorphisms (SNPs) and a copy number variant (CNV) within the NRXN3 genomic region. An initial study was carried out on 157 smokers and 595 controls, all of Spanish Caucasian origin. Nicotine dependence was assessed using the Fagerström index and the number of cigarettes smoked per day. The 45 NRXN3 SNPs genotyped included all the SNPs previously associated with disease, and a previously described deletion within NRXN3. This analysis was replicated in 276 additional independent smokers and 568 controls. Case-control association analyses were performed at the allele, genotype and haplotype levels. Allelic and genotypic association tests showed that three NRXN3 SNPs were associated with a lower risk of being a smoker. The haplotype analysis showed that one block of 16 Kb, consisting of two of the significant SNPs (rs221473 and rs221497), was also associated with lower risk of being a smoker in both the discovery and the replication cohorts, reaching a higher level of significance when the whole sample was considered [odds ratio = 0.57 (0.42-0.77), permuted P = 0.0075]. By contrast, the NRXN3 CNV was not associated with smoking behavior. Taken together, our results confirm a role for NRXN3 in susceptibility to smoking behavior, and strongly implicate this gene in genetic vulnerability to addictive behaviors.

Exploring the proteomes of the venoms of the Peruvian pit vipers Bothrops atrox, B. barnetti and B. pictus

We report the comparative proteomic characterization of the venoms of Bothrops atrox, B. barnetti and B. pictus. The venoms were subjected to RP-HPLC and the resulting fractions analyzed by SDS-PAGE. The proteins were cut from the gels, digested with trypsin and identified via peptide mass fingerprint and manual sequencing of selected peptides by MALDI-TOF/TOF mass spectrometry. Around 20-25 proteins were identified belonging to only 6-7 protein families. Metalloproteinases of the classes P-I and P-III were the most abundant proteins in all venoms (58-74% based on peak area A214 nm), followed by phospholipases-A(2) (6.4-14%), disintegrins (3.2-9%) and serine proteinases (7-11%), and some of these proteins occurred in several isoforms. In contrast cysteine-rich secretory proteins and L-amino acid oxidases appeared only as single isoforms and were found only in B. atrox and B. barnetti. C-type lectins were also detected in all venoms but at low levels (~ 5%). Furthermore, the venoms contain variable numbers of peptides (<3 kDa) and non-protein compounds which were not considered in this work. The protein composition of the investigated Bothrops species is in agreement with their pharmacological and pathological effects.