2D:4D and spatial abilities: From rats to humans

Variance in spatial abilities are thought to be determined by in utero levels of testosterone and oestrogen, measurable in adults by the length ratio of the 2nd and 4th digit (2D:4D). We confirmed the relationship between 2D:4D and spatial performance using rats in two different tasks (paired-associate task and watermaze) and replicated this in humans. We further clarified anatomical and functional brain correlates of the association between 2D:4D and spatial performance in humans.

The Influence of Low-intensity Millimeter-Wave Radiation on the Growth of Cress Roots

An inhibition of growth in cress roots (Lepidium sativum L.) by irradiation with low-intensity millimeter-waves was found using a computer controlled optical system which is capable of measuring nearly continuously the length of the roots to an accuracy of ± 2 jam. The effect is reversible and, for a power density of 6 mWcm-2, results in completely halting the root growth. It occurs within about 100 s after the onset of irradiation. The microwave-induced temperature increase at the surface of the root tip was found to be less than 0.3 °C at this power density. The effect did not show a sharp frequency dependence however it depended strongly on the polariza­tion of the microwaves with respect to the root orientation.

The sensitivity of the root growth to the ambient temperature was examined. Only a weak temperature dependence was found which could not explain the observed effects. However simulating the microwave-induced temperature increase at the surface of the root tip with (incoherent) far-infrared light (λ≥20 μm) resulted in similar effects as with microwaves. Hence one can conclude that the observed effects are primarily caused by the small local irradiation induced thermal gradients across the surface of the root tip.

Sleep timing is more important than sleep length or quality for medical school performance

Overwhelming evidence supports the importance of sleep for memory consolidation. Medical students are often deprived of sufficient sleep due to large amounts of clinical duties and university load, we therefore investigated how study and sleep habits influence university performance. We performed a questionnaire-based study with 31 medical students of the University of Munich (second and third clinical semesters; surgery and internal medicine). The students kept a diary (in 30-min bins) on their daily schedules (times when they studied by themselves, attended classes, slept, worked on their thesis, or worked to earn money). The project design involved three 2-wk periods (A: during the semester; B: directly before the exam period--pre-exam; C: during the subsequent semester break). Besides the diaries, students completed once questionnaires about their sleep quality (Pittsburgh Sleep Quality Index [PSQI]), their chronotype (Munich Chronotype Questionnaire [MCTQ]), and their academic history (previous grades, including the previously achieved preclinical board exam [PBE]). Analysis revealed significant correlations between the actual sleep behavior during the semester (MS(diary); mid-sleep point averaged from the sleep diaries) during the pre-exam period and the achieved grade (p = 0.002) as well as between the grades of the currently taken exam and the PBE (p = 0.002). A regression analysis with MS(diary) pre-exam and PBE as predictors in a model explained 42.7% of the variance of the exam grade (effect size 0.745). Interestingly, MS(diary)--especially during the pre-exam period-was the strongest predictor for the currently achieved grade, along with the preclinical board exam as a covariate, whereas the chronotype did not significantly influence the exam grade.

The interaction between sleep quality and academic performance

Sleep quality has significant effects on cognitive performance and is influenced by multiple factors such as stress. Contrary to the ideal, medical students and residents suffer from sleep deprivation and stress at times when they should achieve the greatest amount of learning. In order to examine the relationship between sleep quality and academic performance, 144 medical students undertaking the pre-clinical board exam answered a survey regarding their subjective sleep quality (Pittsburgh sleep quality index, PSQI), grades and subjective stress for three different time points: semester, pre- and post-exam. Academic performance correlated with stress and sleep quality pre-exam (r = 0.276, p < 0.001 and r = 0.158, p < 0.03, note that low performance meant low sleep quality and high stress), however not with the stress or sleep quality during the semester and post-exam. 59% of all participants exhibited clinically relevant sleep disturbances (PSQI > 5) during exam preparation compared to 29% during the semester and 8% post-exam. This study shows that in medical students it is not the generally poor sleepers, who perform worse in the medical board exams. Instead students who will perform worse on their exams seem to be more stressed and suffer from poor sleep quality. However, poor sleep quality may negatively impact test performance as well, creating a vicious circle. Furthermore, the rate of sleep disturbances in medical students should be cause for intervention.

Far-infrared study of the vibrational modes of 5'-GMP gels and crystals of Na+ and K+

Five Far-Infrared (50-600 cm-1) spectra are presented: the sodium and potassium salts of 5' Guanosine Monophosphate (GMP), each salt in both the gel and crystal conformations, and poly(rG). Measurements were performed at a sample temperature of 10 K under vacuum with a liquid He-cooled bolometer. The spectra were fit with Lorentzians and assignments are suggested. There are noteworthy differences in oscillator strengths and frequencies of the bands between all spectra. We report the tentative observation of a 100 cm-1 mode which is in the neighborhood of a mode observed by Raman spectroscopy in solution (1) and dried gels (2).

Broadband, Non-Thermal Millimeter-Wave Influence on Giant Chromosomes

A non-thermal influence of low-intensity millimeter-wave radiation on the puffing of giant chromosom es from salivary glands of larvae of the midge A cricotopus lucidus (Diptera, Chironomidae) is reported. The effect is manifested as a strong regression in size of a specific puff that expresses genes for a secretory protein (Fig. 1). While millimeter-wave irradiation leads to an about tenfold increase of the regression probability com pared to controls, simulation of the small microwave-induced temperature increase in the sample does not result in a significant effect, thus confirming the non-thermal nature of the microwave irradiation effect. This finding could be of importance for the understanding of the interaction between microwave radiation and living systems and hence for the establishment of safety standards in that frequency regime.

Picosecond relaxations in hydrated lysozyme observed by mm-wave spectroscopy

Dielectric absorption measurements at mm-wave frequencies (50 GHz. . . 150 GHz) are reported for lysozyme at different hydration levels. The measurements were extended over the temperature range from liquid helium to room temperature using the untuned cavity technique. For dried lysozyme (water content less than or equal to 0.5%, w/w) a nearly linear increase with frequency and an exponential increase with temperature of the absorption coefficient is observed between 50 K and 300 K. This frequency and temperature dependence is described by relaxation processes in asymmetric double-well potentials with relaxation times in the picosecond range. Hydration yields a nearly frequency-independent contribution to the absorption, which arises only at temperatures above 120 K. The frequency independence indicates relaxation rates for the bound water that are small compared to mm-wave frequencies. Thereby the contribution of bound water can clearly be distinguished from the fast intrinsic processes. An assignment of these picosecond relaxations to the NH . . . OC hydrogen bond of the peptide backbone is suggested.

Search for millimeter microwave effects on enzyme or protein functions

Recent observations of nonthermal, resonant biological responses to weak millimeter microwave irradiation have led us to investigate whether similar influences exist on enzymatic functions in vitro. We chose (i) the reduction of ethanol in the presence of alcohol dehydrogenase and (ii) the cooperative binding of oxygen on hemoglobin. Using an irradiation intensity near 10 mW/cm2 the frequency was continuously varied from 40 to 115 GHz with a resolution of a few MHz. No microwave influences were detectable within our experimental sensitivity of about 0.1% of the reaction rate in (i), or of the amount of bound oxygen at half saturation in (ii).

Tilt-compensated Michelson interferometer for Fourier transform spectroscopy

A new Michelson interferometer built exclusively with spherical and plane mirrors provides tilt compensation for all mirrors. In particular, a staggering of the movable mirror generates no shift of the two images obtained from the two interferometer arms on the detector area. These properties are experimentally demonstrated by taking interferograms from a near ir source. The influence of small tilts of the movable component on the optical path difference is analyzed.