Secondary Instabilities of Surface Waves on Viscous Fluids in the Faraday Instability

Secondary instabilities of Faraday waves show three regimes: (1) As seen previously, low-viscosity (nu) fluids destabilize first into squares. At higher driving accelerations a, squares show low-frequency modulations corresponding to the motion of phase defects, while theory predicts a stationary transverse amplitude modulation (TAM). (2) High-nu fluids destabilize first to stripes. Stripes then show an oscillatory TAM whose frequency is incommensurate with the driving frequency. At higher a, the TAM undergoes a phase instability. At still higher a, edge dislocations form and fluid droplets are ejected. (3) Intermediate-nu fluids show a complex coexistence of squares and stripes, as well as stationary and oscillatory TAM instabilities of the stripes.Comment: REVTEX, with 3 separate uuencoded figures, to appear in Europhys. Let

Caracter?sticas de las cartas al editor publicadas en revistas de educaci?n m?dica editadas en espa?ol, 2015-2020

Introducci?n: Los lectores manifiestan sus comentariosen forma de cartas al editor sobre art?culos previamente publicados, de investigaciones originales que no llegan al art?culo original o sobre temas generales que requieren atenci?n debido a su novedad. Ello tiene la posibilidad de recibir una respuesta en forma de r?plica. Objetivo: Describir las caracter?sticas de las cartas al editor publicadas durante el periodo 2015-2020 en las revistas de educaci?n m?dica en espa?ol indizadas en SciELO o Scopus. M?todo: Estudio descriptivo, retrospectivo y de tipo bibliom?trico de las cartas al editor de las revistas: Educaci?n M?dica, Educaci?n M?dica Superior, Investigaci?n en Educaci?n M?dica y la Revista de la Fundaci?n Educaci?n M?dica. El periodo abarcado fue de enero de 2015 a diciembre de 2020. Resultados: El promedio anual de cartas al editor fuede 13.23%, con un valor m?nimo de 6.58%, en 2015; y m?ximo de 18.41%, en 2018. La filiaci?n institucional de universidades fue la m?s frecuente (84.71%). La mayor?a de autores ten?a filiaci?n peruana (43.80%) y el sexo masculino (78.93%). Las cartas redactadas en idioma espa?ol fueron el 99.59%. En relaci?n con el prop?sito general, predominaron las de comentario general (42.56%) y comentarios sobre art?culos previamente publicados (40.50%). La media de citas fue de 4.24 y la de hallazgos propios tuvo la mayor media con 6.39. ?nicamente 11 cartas tuvieron r?plicas. La media de autores fue 2.02. Conclusiones: La publicaci?n de cartas al editor tuvo un incremento con los a?os, sigue siendo frecuente su uso como medio de cr?tica; sin embargo, no se vio frecuente la retroalimentaci?n e intercambio de ideas a trav?s de la r?plica.Introduction: Readers express their comments in the form of letters to the editor about previously published articles, original research that does not reach the original article, or general topics that require attention because of their novelty. It has the possibility of receiving a response in the form of a reply. Objective: Describe the characteristics of the letters to the editor published during the period 2015-2020 in the journals of medical education in Spanish indexed in SciELO or Scopus. Method: A descriptive, retrospective, and bibliometric study of the letters to the editor of the journals: Educaci?n M?dica, Educaci?n M?dica Superior, Investigaci?n en Educaci?n M?dica y la Revista de la Fundaci?n Educaci?n M?dica. The period covered was from January 2015 to December 2020. Results: The annual average of letters to the editor was 13.23%, with a minimum value of 6.58% in 2015 and a maximum of 18.41% in 2018. The institutional affiliation of universities was the most frequent (84.71%). The majority of authors had Peruvian affiliation (43.80%) and the male sex (78.93%). The letters written in Spanish were 99.59%. In relation to the general purpose, the general comments (42.56%) and comments on previously published articles (40.50%) predominated. The average number of citations was 4.24, with own findings having the highest average at 6.39. Only 11 letters had replies. The average number of authors was 2.02. Conclusions: The publication of letters to the editor had an increase over the years, its use as a means of criticism is still frequent; however, feedback and exchange of ideas through replication was not frequent

Exciton bimolecular annihilation dynamics in supramolecular nanostructures of conjugated oligomers

We present femtosecond transient absorption measurements on $\pi$-conjugated supramolecular assemblies in a high pump fluence regime. Oligo(\emph{p}-phenylenevinylene) monofunctionalized with ureido-\emph{s}-triazine (MOPV) self-assembles into chiral stacks in dodecane solution below 75$^{\circ}$C at a concentration of $4\times 10^{-4}$ M. We observe exciton bimolecular annihilation in MOPV stacks at high excitation fluence, indicated by the fluence-dependent decay of $1^1$B$_{u}$-exciton spectral signatures, and by the sub-linear fluence dependence of time- and wavelength-integrated photoluminescence (PL) intensity. These two characteristics are much less pronounced in MOPV solution where the phase equilibrium is shifted significantly away from supramolecular assembly, slightly below the transition temperature. A mesoscopic rate-equation model is applied to extract the bimolecular annihilation rate constant from the excitation fluence dependence of transient absorption and PL signals. The results demonstrate that the bimolecular annihilation rate is very high with a square-root dependence in time. The exciton annihilation results from a combination of fast exciton diffusion and resonance energy transfer. The supramolecular nanostructures studied here have electronic properties that are intermediate between molecular aggregates and polymeric semiconductors

Effect of Oral Alendronate on Bone Mineral Density and the Incidence of Fractures in Postmenopausal Osteoporosis

BACKGROUND Postmenopausal osteoporosis is a serious health problem, and additional treatments are needed. METHODS We studied the effects of oral alendronate, an aminobisphosphonate, on bone mineral density and the incidence of fractures and height loss in 994 women with postmenopausal osteoporosis. The women were treated with placebo or alendronate (5 or 10 mg daily for three years, or 20 mg for two years followed by 5 mg for one year); all the women received 500 mg of calcium daily. Bone mineral density was measured by dual-energy x-ray absorptiometry. The occurrence of new vertebral fractures and the progression of vertebral deformities were determined by an analysis of digitized radiographs, and loss of height was determined by sequential height measurements. RESULTS The women receiving alendronate had significant, progressive increases in bone mineral density at all skeletal sites, whereas those receiving placebo had decreases in bone mineral density. At three years, the mean (±SE) differences in bone mineral density between the women receiving 10 mg of alendronate daily and those receiving placebo were 8.8±0.4 percent in the spine, 5.9±0.5 percent in the femoral neck, 7.8±0.6 percent in the trochanter, and 2.5±0.3 percent in the total body (P CONCLUSIONS Daily treatment with alendronate progressively increases the bone mass in the spine, hip, and total body and reduces the incidence of vertebral fractures, the progression of vertebral deformities, and height loss in postmenopausal women with osteoporosis

Reproductive Outcomes Following Ectopic Pregnancy: Register-Based Retrospective Cohort Study

Using Scottish national registry data, Sohinee Bhattacharya and colleagues investigate pregnancy outcomes following ectopic pregnancy in comparison to livebirth, miscarriage, or termination in a first pregnancy

Impact of cognitive stimulation on ripples within human epileptic and non-epileptic hippocampus

Background: Until now there has been no way of distinguishing between physiological and epileptic hippocampal ripples in intracranial recordings. In the present study we addressed this by investigating the effect of cognitive stimulation on interictal high frequency oscillations in the ripple range (80-250 Hz) within epileptic (EH) and non-epileptic hippocampus (NH). Methods: We analyzed depth EEG recordings in 10 patients with intractable epilepsy, in whom hippocampal activity was recorded initially during quiet wakefulness and subsequently during a simple cognitive task. Using automated detection of ripples based on amplitude of the power envelope, we analyzed ripple rate (RR) in the cognitive and resting period, within EH and NH. Results: Compared to quiet wakefulness we observed a significant reduction of RR during cognitive stimulation in EH, while it remained statistically marginal in NH. Further, we investigated the direct impact of cognitive stimuli on ripples (i.e. immediately post-stimulus), which showed a transient statistically significant suppression of ripples in the first second after stimuli onset in NH only. Conclusion: Our results point to a differential reactivity of ripples within EH and NH to cognitive stimulation

Neural Computation via Neural Geometry: A Place Code for Inter-whisker Timing in the Barrel Cortex?

The place theory proposed by Jeffress (1948) is still the dominant model of how the brain represents the movement of sensory stimuli between sensory receptors. According to the place theory, delays in signalling between neurons, dependent on the distances between them, compensate for time differences in the stimulation of sensory receptors. Hence the location of neurons, activated by the coincident arrival of multiple signals, reports the stimulus movement velocity. Despite its generality, most evidence for the place theory has been provided by studies of the auditory system of auditory specialists like the barn owl, but in the study of mammalian auditory systems the evidence is inconclusive. We ask to what extent the somatosensory systems of tactile specialists like rats and mice use distance dependent delays between neurons to compute the motion of tactile stimuli between the facial whiskers (or ‘vibrissae’). We present a model in which synaptic inputs evoked by whisker deflections arrive at neurons in layer 2/3 (L2/3) somatosensory ‘barrel’ cortex at different times. The timing of synaptic inputs to each neuron depends on its location relative to sources of input in layer 4 (L4) that represent stimulation of each whisker. Constrained by the geometry and timing of projections from L4 to L2/3, the model can account for a range of experimentally measured responses to two-whisker stimuli. Consistent with that data, responses of model neurons located between the barrels to paired stimulation of two whiskers are greater than the sum of the responses to either whisker input alone. The model predicts that for neurons located closer to either barrel these supralinear responses are tuned for longer inter-whisker stimulation intervals, yielding a topographic map for the inter-whisker deflection interval across the surface of L2/3. This map constitutes a neural place code for the relative timing of sensory stimuli

Finding the engram.

Many attempts have been made to localize the physical trace of a memory, or engram, in the brain. However, until recently, engrams have remained largely elusive. In this Review, we develop four defining criteria that enable us to critically assess the recent progress that has been made towards finding the engram. Recent \u27capture\u27 studies use novel approaches to tag populations of neurons that are active during memory encoding, thereby allowing these engram-associated neurons to be manipulated at later times. We propose that findings from these capture studies represent considerable progress in allowing us to observe, erase and express the engram

Temporal trends in fetal mortality at and beyond term and induction of labor in Germany 2005-2012 : data from German routine perinatal monitoring

Purpose: While a variety of factors may play a role in fetal and neonatal deaths, postmaturity as a cause of stillbirth remains a topic of debate. It still is unclear, whether induction of labor at a particular gestational age may prevent fetal deaths. Methods: A multidisciplinary working group was granted access to the most recent set of relevant German routine perinatal data, comprising all 5,291,011 hospital births from 2005 to 2012. We analyzed correlations in rates of induction of labor (IOL), perinatal mortality (in particular stillbirths) at different gestational ages, and fetal morbidity. Correlations were tested with Pearson's product-moment analysis (α = 5 %). All computations were performed with SPSS version 22. Results: Induction rates rose significantly from 16.5 to 21.9 % (r = 0.98; p \ 0.001). There were no significant changes in stillbirth rates (0.28-0.35 per 100 births; r = 0.045; p = 0.806). Stillbirth rates 2009-2012 remained stable in all gestational age groups irrespective of induction. Fetal morbidity (one or more ICD-10 codes) rose significantly during 2005–2012. This was true for both children with (from 33 to 37 %, r = 0.784, p \ 0.001) and without (from 25 to 31 %, (r = 0.920, p \ 0.001) IOL. Conclusions: An increase in IOL at term is not associated with a decline in perinatal mortality. Perinatal morbidity increased with and without indiction of labor