Intersystem crossing rates of S1 state keto-amino cytosine at low excess energy

The amino-keto tautomer of supersonic jet-cooled cytosine undergoes intersystem crossing (ISC) from the v = 0 and low-lying vibronic levels of its S1(¹ππ*) state. We investigate these ISC rates experimentally and theoretically as a function of S1 state vibrational excess energy Eexc. The S1 vibronic levels are pumped with a ~5 ns UV laser, the S1 and triplet state ion signals are separated by prompt or delayed ionization with a second UV laser pulse. After correcting the raw ISC yields for the relative S1 and T1ionization cross sections, we obtain energy dependent ISC quantum yields Q corr ISC =1% –5%. These are combined with previously measured vibronic state-specific decay rates, giving ISC rates kISC = 0.4–1.5 ⋅ 10⁹ s⁻¹, the corresponding S1⇝S0internal conversion (IC) rates are 30–100 times larger. Theoretical ISC rates are computed using SCS-CC2 methods, which predict rapid ISC from the S1; v = 0 state with kISC = 3 ⋅ 10⁹ s⁻¹ to the T1(³ππ*) triplet state. The surprisingly high rate of this El Sayed-forbidden transition is caused by a substantial admixture of ¹nOπ* character into the S1(¹ππ*) wave function at its non-planar minimum geometry. The combination of experiment and theory implies that (1) below Eexc = 550 cm⁻¹ in the S1 state, S1⇝S0internal conversion dominates the nonradiative decay with kIC ≥ 2 ⋅ 10¹⁰ s⁻¹, (2) the calculated S1⇝T1 (¹ππ*⇝³ππ*) ISC rate is in good agreement with experiment, (3) being El-Sayed forbidden, the S1⇝T1 ISC is moderately fast (kISC = 3 ⋅ 10⁹ s⁻¹), and not ultrafast, as claimed by other calculations, and (4) at Eexc ~ 550 cm⁻¹ the IC rate increases by ~50 times, probably by accessing the lowest conical intersection (the C5-twist CI) and thereby effectively switching off the ISC decay channels.

The elusive S2 state, the S1/S2 splitting, and the excimer states of the benzene dimer

We observe the weak S 0 → S 2 transitions of the T-shaped benzene dimers (Bz)2 and (Bz-d 6)2 about 250 cm−1 and 220 cm−1 above their respective S 0 → S 1 electronic origins using two-color resonant two-photon ionization spectroscopy. Spin-component scaled (SCS) second-order approximate coupled-cluster (CC2) calculations predict that for the tipped T-shaped geometry, the S 0 → S 2 electronic oscillator strength f el (S 2) is ∼10 times smaller than f el (S 1) and the S 2 state lies ∼240 cm−1 above S 1, in excellent agreement with experiment. The S 0 → S 1 (ππ ∗) transition is mainly localized on the “stem” benzene, with a minor stem → cap charge-transfer contribution; the S 0 → S 2 transition is mainly localized on the “cap” benzene. The orbitals, electronic oscillator strengths f el (S 1) and f el (S 2), and transition frequencies depend strongly on the tipping angle ω between the two Bz moieties. The SCS-CC2 calculated S 1 and S 2 excitation energies at different T-shaped, stacked-parallel and parallel-displaced stationary points of the (Bz)2 ground-state surface allow to construct approximate S 1 and S 2 potential energy surfaces and reveal their relation to the “excimer” states at the stacked-parallel geometry. The f el (S 1) and f el (S 2) transition dipole moments at the C 2v -symmetric T-shape, parallel-displaced and stacked-parallel geometries are either zero or ∼10 times smaller than at the tipped T-shaped geometry. This unusual property of the S 0 → S 1 and S 0 → S 2 transition-dipole moment surfaces of (Bz)2 restricts its observation by electronic spectroscopy to the tipped and tilted T-shaped geometries; the other ground-state geometries are impossible or extremely difficult to observe. The S 0 → S 1/S 2 spectra of (Bz)2 are compared to those of imidazole ⋅ (Bz)2, which has a rigid triangular structure with a tilted (Bz)2 subunit. The S 0 → S 1/ S 2 transitions of imidazole-(benzene)2 lie at similar energies as those of (Bz)2, confirming our assignment of the (Bz)2 S 0 → S 2 transition.

European S1 guideline for the treatment of hidradenitis suppurativa/acne inversa

Hidradenitis suppurativa/acne inversa (HS) is a chronic, inflammatory, recurrent, debilitating skin disease of the hair follicle that usually presents after puberty with painful, deep-seated, inflamed lesions in the apocrine gland-bearing areas of the body, most commonly the axillae, inguinal and anogenital regions. A mean disease incidence of 6.0 per 100,000 person-years and an average prevalence of 1% has been reported in Europe. HS has the highest impact on patients' quality of life among all assessed dermatological diseases. HS is associated with a variety of concomitant and secondary diseases, such as obesity, metabolic syndrome, inflammatory bowel disease, e.g. Crohn's disease, spondyloarthropathy, follicular occlusion syndrome and other hyperergic diseases. The central pathogenic event in HS is believed to be the occlusion of the upper part of the hair follicle leading to a perifollicular lympho-histiocytic inflammation. A highly significant association between the prevalence of HS and current smoking (Odds ratio 12.55) and overweight (Odds ratio 1.1 for each body mass index unit) has been documented. The European S1 HS guideline suggests that the disease should be treated based on its individual subjective impact and objective severity. Locally recurring lesions can be treated by classical surgery or LASER techniques, whereas medical treatment either as monotherapy or in combination with radical surgery is more appropriate for widely spread lesions. Medical therapy may include antibiotics (clindamycin plus rifampicine, tetracyclines), acitretin and biologics (adalimumab, infliximab). A Hurley severity grade-relevant treatment of HS is recommended by the expert group following a treatment algorithm. Adjuvant measurements, such as pain management, treatment of superinfections, weight loss and tobacco abstinence have to be considered.

(Table S1) Diatom species richness from the Early Pleistocene to present

The extent to which the spatial distribution of marine planktonic microbes is controlled by local environmental selection or dispersal is poorly understood. Our ability to separate the effects of these two biogeographic controls is limited by the enormous environmental variability both in space and through time. To circumvent this limitation, we analyzed fossil diatom assemblages over the past ~1.5 million years from the world oceans and show that these eukaryotic microbes are not limited by dispersal. The lack of dispersal limitation in marine diatoms suggests that the biodiversity at the microbial level fundamentally differs from that of macroscopic animals and plants for which geographic isolation is a common component of speciation.

Nd isotope data for planktonic foraminifera from within and around sapropels S1 and S5 from ODP Site 160-967

The development of widespread anoxic conditions in the deep oceans is evidenced by the accumulation and preservation of organic-carbon-rich sediments, but its precise cause remains controversial. The two most popular hypotheses involve (1) circulation-induced increased stratification resulting in reduced oxygenation of deep waters or (2) enhanced productivity in the surface ocean, increasing the raining down of organic matter and overwhelming the oxic remineralization potential of the deep ocean. In the periodic development of deep-water anoxia in the Pliocene-Pleistocene Mediterranean Sea, increased riverine runoff has been implicated both as a source for nutrients that fuel enhanced photic-zone productivity and a source of a less dense freshwater cap leading to reduced circulation, basin-wide stagnation, and deep-water oxygen starvation. Monsoon-driven increases in Nile River discharge and increased regional precipitation due to enhanced westerly activity-two mechanisms that represent fundamentally different climatic driving forces-have both been suggested as causes of the altered freshwater balance. Here we present data that confirm a distinctive neodymium (Nd) isotope signature for the Nile River relative to the Eastern Mediterranean-providing a new tracer of enhanced Nile outflow into the Mediterranean in the past. We further present Nd isotope data for planktonic foraminifera that suggest a clear increase in Nile discharge during the central intense period of two recent anoxic events. Our data also suggest, however, that other regional freshwater sources were more important at the beginning and end of the anoxic events. Taken at face value, the data appear to imply a temporal link between peaks in Nile discharge and enhanced westerly activity.

(Table S1) Age determination of Emperor Seamounts basement

The Hawaiian-Emperor hotspot track has a prominent bend, which has served as the basis for the theory that the Hawaiian hotspot, fixed in the deep mantle, traced a change in plate motion. However, paleomagnetic and radiometric age data from samples recovered by ocean drilling define an age-progressive paleolatitude history, indicating that the Emperor Seamount trend was principally formed by the rapid motion (over 40 millimeters per year) of the Hawaiian hotspot plume during Late Cretaceous to early-Tertiary times (81 to 47 million years ago). Evidence for motion of the Hawaiian plume affects models of mantle convection and plate tectonics, changing our understanding of terrestrial dynamics.

(Data S1) Palynological analysis of IODP and ODP sediment cores around the Antarctic margin

The circum-Antarctic Southern Ocean is an important region for global marine food webs and carbon cycling because of sea-ice formation and its unique plankton ecosystem. However, the mechanisms underlying the installation of this distinct ecosystem and the geological timing of its development remain unknown. Here, we show, on the basis of fossil marine dinoflagellate cyst records, that a major restructuring of the Southern Ocean plankton ecosystem occurred abruptly and concomitant with the first major Antarctic glaciation in the earliest Oligocene (~33.6 million years ago). This turnover marks a regime shift in zooplankton-phytoplankton interactions and community structure, which indicates the appearance of eutrophic and seasonally productive environments on the Antarctic margin. We conclude that earliest Oligocene cooling, ice-sheet expansion, and subsequent sea-ice formation were important drivers of biotic evolution in the Southern Ocean.