Random Sequential Adsorption on Fractals

Irreversible adsorption of spheres on flat collectors having dimension $d<2$ is studied. Molecules are adsorbed on Sierpinski's Triangle and Carpet like fractals ($1<d<2$), and on General Cantor Set ($d<1$). Adsorption process is modeled numerically using Random Sequential Adsorption (RSA) algorithm. The paper concentrates on measurement of fundamental properties of coverages, i.e. maximal random coverage ratio and density autocorrelation function, as well as RSA kinetics. Obtained results allow to improve phenomenological relation between maximal random coverage ratio and collector dimension. Moreover, simulations show that, in general, most of known dimensional properties of adsorbed monolayers are valid for non-integer dimensions.Comment: 12 pages, 8 figure

Tracing the Ingredients for a Habitable Earth from Interstellar Space through Planet Formation

We use the C/N ratio as a monitor of the delivery of key ingredients of life to nascent terrestrial worlds. Total elemental C and N contents, and their ratio, are examined for the interstellar medium, comets, chondritic meteorites and terrestrial planets; we include an updated estimate for the Bulk Silicate Earth (C/N = 49.0 +/- 9.3). Using a kinetic model of disk chemistry, and the sublimation/condensation temperatures of primitive molecules, we suggest that organic ices and macro-molecular (refractory or carbonaceous dust) organic material are the likely initial C and N carriers. Chemical reactions in the disk can produce nebular C/N ratios of ~1-12, comparable to those of comets and the low end estimated for planetesimals. An increase of the C/N ratio is traced between volatile-rich pristine bodies and larger volatile-depleted objects subjected to thermal/accretional metamorphism. The C/N ratios of the dominant materials accreted to terrestrial planets should therefore be higher than those seen in carbonaceous chondrites or comets. During planetary formation, we explore scenarios leading to further volatile loss and associated C/N variations owing to core formation and atmospheric escape. Key processes include relative enrichment of nitrogen in the atmosphere and preferential sequestration of carbon by the core. The high C/N BSE ratio therefore is best satisfied by accretion of thermally processed objects followed by large-scale atmospheric loss. These two effects must be more profound if volatile sequestration in the core is effective. The stochastic nature of these processes hints that the surface/atmospheric abundances of biosphere-essential materials will likely be variable.Comment: Accepted by PNAS per http://www.pnas.org/content/early/2015/07/01/1500954112.abstract?sid=9fd8abea-9d33-46d8-b755-217d10b1c24

Destruction of Refractory Carbon in Protoplanetary Disks

The Earth and other rocky bodies in the inner solar system contain significantly less carbon than the primordial materials that seeded their formation. These carbon-poor objects include the parent bodies of primitive meteorites, suggesting that at least one process responsible for solid-phase carbon depletion was active prior to the early stages of planet formation. Potential mechanisms include the erosion of carbonaceous materials by photons or atomic oxygen in the surface layers of the protoplanetary disk. Under photochemically generated favorable conditions, these reactions can deplete the near-surface abundance of carbon grains and polycyclic aromatic hydrocarbons by several orders of magnitude on short timescales relative to the lifetime of the disk out to radii of ~20-100+ au from the central star depending on the form of refractory carbon present. Due to the reliance of destruction mechanisms on a high influx of photons, the extent of refractory carbon depletion is quite sensitive to the disk's internal radiation field. Dust transport within the disk is required to affect the composition of the midplane. In our current model of a passive, constant-alpha disk, where alpha = 0.01, carbon grains can be turbulently lofted into the destructive surface layers and depleted out to radii of ~3-10 au for 0.1-1 um grains. Smaller grains can be cleared out of the planet-forming region completely. Destruction may be more effective in an actively accreting disk or when considering individual grain trajectories in non-idealized disks.Comment: 15 pages, 9 figures, Accepted for publication in Ap

How Changes in Depression and Anxiety Symptoms Correspond to Variations in Female Sexual Response in a Nonclinical Sample of Young Women: A Daily Diary Study

Introduction A large body of literature supports the co‐occurrence of depression, anxiety, and sexual dysfunction. However, the manner in which affective symptoms map onto specific female sexual response indices is not well understood. Aims The present study aimed to examine changes in depression and anxiety symptoms and their correspondence to fluctuations in desire, subjective arousal, genital response, orgasmic function, and vaginal pain. Methods The study used a 2‐week daily diary approach to examine same‐day and temporal relations between affective symptoms and sexual function. Main Outcome Measures The unique relations between shared and disorder‐specific symptoms of depression and anxiety (i.e., general distress, anhedonia, and anxious arousal) and female sexual response (i.e., desire, subjective arousal, vaginal lubrication, orgasmic function, and sexual pain) were examined, controlling for baseline levels of sexual distress, depression, and anxiety, as well as age effects and menstruation. Results Analyses revealed that changes in depression and anxiety severity corresponded to same‐day variations in sexual response. Specifically, anhedonia (depression‐specific symptom) was related to poorer same‐day sexual desire, whereas greater anxious arousal (anxiety‐specific symptom) was independently related to simultaneous increases in subjective sexual arousal, vaginal lubrication, and sexual pain. Increases in general distress (i.e., shared symptoms) were associated with greater same‐day difficulties achieving orgasm. Notably, only one temporal relation was found; it indicated that higher levels of anhedonia predicted a next‐day decrease in sexual desire. Conclusions It is proposed that the simultaneous changes in affective symptoms and sexual function may indicate that they are products of shared underlying mechanisms. That is, in response to stress, the processes manifesting as feelings of weak positive affect and amotivation are the very same processes responsible for diminished capacity for sexual desire. In contrast, the physiological hyperarousal associated with anxiety also gives rise to sexual arousal difficulties and vaginal pain. Kalmbach DA, Kingsberg SA, and Ciesla JA. How changes in depression and anxiety symptoms correspond to variations in female sexual response in a nonclinical sample of young women: A daily diary study. J Sex Med 2014;11:2915–2927.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109992/1/jsm12692.pd

Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar Nebula

Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments they were exposed to. We found that icy grains originating in the outer disk, where temperatures were less than 30 K, experienced UV irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural byproducts of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own

The Impact of Sleep on Female Sexual Response and Behavior: A Pilot Study

IntroductionThe etiological role of sleep disturbance in sexual difficulties has been largely overlooked. Research suggests that short sleep duration and poor sleep quality lead to poor female sexual response. However, prior research consists of cross‐sectional studies, and the influence of sleep on sexual functioning and behavior has not been prospectively examined.AimWe sought to examine the influence of nightly sleep duration, sleep quality, and sleep onset latency on daily female sexual response and activity.MethodsThis study used a longitudinal design to study 171 women free of antidepressants and with reliable Internet access who were recruited from a university setting in the United States. Participants first completed baseline measures in a laboratory, and then completed web‐delivered surveys at their habitual wake time for 14 consecutive days.Main Outcome MeasuresAll outcome measures were modified for daily recall. Participants completed the Profile of Female Sexual Function's desire, subjective arousal, and orgasmic functioning scales and the Female Sexual Function Index's genital arousal scale, and indicated whether they engaged in partnered sexual activity or self‐stimulation in response to dichotomous items.ResultsAnalyses revealed that longer sleep duration was related to greater next‐day sexual desire (b = 0.32, P = 0.02), and that a 1‐hour increase in sleep length corresponded to a 14% increase in odds of engaging in partnered sexual activity (odds ratio = 1.14, P < 0.05). In contrast, sleeping longer predicted poorer next‐day genital arousal (b = −0.19, P < 0.01). However, results showed that women with longer average sleep duration reported better genital arousal than women with shorter average sleep length (b = 0.54, P = 0.03).ConclusionsObtaining sufficient sleep is important to the promotion of healthy sexual desire and genital response, as well as the likelihood of engaging in partnered sexual activity. These relationships were independent of daytime affect and fatigue. Future directions may investigate sleep disorders as risk factors for sexual dysfunction. Kalmbach DA, Arnedt JT, Pillai V, and Ciesla JA. The impact of sleep on female sexual response and behavior: A pilot study. J Sex Med 2015;12:1221–1232.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111751/1/jsm12858.pd

Studying the evolution of galaxies in compact groups over the past 3 Gyr - II. The importance of environment in the suppression of star formation

We present an in depth study on the evolution of galaxy properties in compact groups over the past 3 Gyr. We are using the largest multi-wavelength sample to-date, comprised 1770 groups (containing 7417 galaxies), in the redshift range of 0.01<z<0.23. To derive the physical properties of the galaxies we rely on ultraviolet (UV)-to-infrared spectral energy distribution modeling, using CIGALE. Our results suggest that during the 3 Gyr period covered by our sample, the star formation activity of galaxies in our groups has been substantially reduced (3-10 times). Moreover, their star formation histories as well as their UV-optical and mid-infrared colors are significantly different from those of field and cluster galaxies, indicating that compact group galaxies spend more time transitioning through the green valley. The morphological transformation from late-type spirals into early-type galaxies occurs in the mid-infrared transition zone rather than in the UV-optical green valley. We find evidence of shocks in the emission line ratios and gas velocity dispersions of the late-type galaxies located below the star forming main sequence. Our results suggest that in addition to gas stripping, turbulence and shocks might play an important role in suppressing the star formation in compact group galaxies.Comment: (Accepted for publication in MNRAS, date of submission November 18, 2015