Females tend to threaten each other with social isolation rather than violence. Among social animals, being cast out of the group can mean death, or very few chances to mate. Among humans, perhaps the most social animals we know, the "mean girls" phenomenon is a perfect example of low energy competition. Nobody is beaten, but we know for sure who has lost the battle.
The problem with talking about humans, of course, is that we are not wild animals. As Stockley and Campbell are careful to point out, humans have been so influenced by culture that it's very hard to tell if a lack of overt aggression among women is an evolutionary or cultural artifact. Because so many women are culturally trained to tamp down their aggressive urges, it's impossible to call their behavior "natural."
So it's difficult to draw many conclusions about how early human women might have behaved 50,000 years ago based on how they behave today.
To return to the world of animals, it's interesting to note that females seem to be aggressive in a much more flexible way than males. As I mentioned earlier, female mice go through periodic spikes in aggressive behavior, partly as a result of hormonal shifts.
Females also become more aggressive when they are defending their young . That's likely because the hormone oxytocin, released during and after pregnancy, isn't just a "love hormone" to spur mother/child bonding. It also governs aggression. So in the wake of pregnancy, when oxytocin levels are high, females are simultaneously more nurturing and more likely to go ninja on your ass.
Overall, however, female aggression and competition are more subtle than the male forms. Females assert dominance, and come to control the gene pool, by fostering cooperation. This is especially true among social animals who live at a high population size. Of course, cooperation isn't all happy "friendship is magic" stuff. A cooperative female may cede her reproductive privileges to another.
It's a low cost solution to a problem as old as life itself. Put another way, just because females don't grow giant horns doesn't mean they aren't ripping each other's hearts out.
Obviously these tactics aren't universally used as there is female violence, but what would the murder rate and frequency of war be if men somehow adopted these tactics? Does culture in some societies create a pathway to these tactics?
String Theory - The Physics of String-Bending and Other Electric Guitar Techniques
David Robert Grimes
Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.
Looking at the metabolic costs of running and the burden of arms. The paper is behind a paywall - the estimate of the metabolic cost of arms seems a bit contrived in this disucssion (the paper may be robust), but the overall conclusion seems reasonable.
The metabolic cost of human running: is swinging the arms worth it?
Christopher J. Arellano1,2,* and Rodger Kram1
1Integrative Physiology Department, University of Colorado, Boulder, CO 80309, USA 2Ecology and Evolutionary Biology Department, Brown University, Providence, RI 02912, USA
Although the mechanical function is quite clear, there is no consensus regarding the metabolic benefit of arm swing during human running. We compared the metabolic cost of running using normal arm swing with the metabolic cost of running while restricting the arms in three different ways: (1) holding the hands with the arms behind the back in a relaxed position (BACK), (2) holding the arms across the chest (CHEST) and (3) holding the hands on top of the head (HEAD). We hypothesized that running without arm swing would demand a greater metabolic cost than running with arm swing. Indeed, when compared with running using normal arm swing, we found that net metabolic power demand was 3, 9 and 13% greater for the BACK, CHEST and HEAD conditions, respectively (all P<0.05). We also found that when running without arm swing, subjects significantly increased the peak-to-peak amplitudes of both shoulder and pelvis rotation about the vertical axis, most likely a compensatory strategy to counterbalance the rotational angular momentum of the swinging legs. In conclusion, our findings support our general hypothesis that swinging the arms reduces the metabolic cost of human running. Our findings also demonstrate that arm swing minimizes torso rotation. We infer that actively swinging the arms provides both metabolic and biomechanical benefits during human running.
The shape of sandstone arches is usually explained by natural weathering. It turns out erosion removes material, but the shape is strongly influenced by gravity. A paper in Nature Geoscience postulates erosion removes some material that would normally cause collapse, but pressue increases on the remaining material causing its sandgrains to lock into a more stable and resilient configuration.
Sandstone landforms shaped by negative feedback between stress and erosion
Jiri Bruthans, Jan Soukup, Jana Vaculikova, Michal Filippi, Jana Schweigstillova, Alan L. Mayo, David Masin, Gunther Kletetschka & Jaroslav Rihosek
Nature Geoscience (2014) doi:10.1038/ngeo2209
Weathering and erosion of sandstone produces unique landforms1, 2 such as arches, alcoves, pedestal rocks and pillars. Gravity-induced stresses have been assumed to not play a role in landform preservation3 and to instead increase weathering rates4, 5. Here we show that increased stress within a landform as a result of vertical loading reduces weathering and erosion rates, using laboratory experiments and numerical modelling. We find that when a cube of locked sand exposed to weathering and erosion processes is experimentally subjected to a sufficiently low vertical stress, the vertical sides of the cube progressively disintegrate into individual grains. As the cross-sectional area under the loading decreases, the vertical stress increases until a critical value is reached. At this threshold, fabric interlocking of sand grains causes the granular sediment to behave like a strong, rock-like material, and the remaining load-bearing pillar or pedestal landform is resistant to further erosion. Our experiments are able to reproduce other natural shapes including arches, alcoves and multiple pillars when planar discontinuities, such as bedding planes or fractures, are present. Numerical modelling demonstrates that the stress field is modified by discontinuities to make a variety of shapes stable under fabric interlocking, owing to the negative feedback between stress and erosion. We conclude that the stress field is the primary control of the shape evolution of sandstone landforms.
A new study quantifies the urban heat island effect - some notes here.
The press release:
Contact: Kevin Dennehy firstname.lastname@example.org 203-436-4842 Yale School of Forestry & Environmental Studies Urban heat -- not a myth, and worst where it's wet
Study quantifies the primary causes of the urban heat island effect
A new Yale-led study quantifies for the first time the primary causes of the "urban heat island" (UHI) effect, a common phenomenon that makes the world's urban areas significantly warmer than the surrounding countryside and may increase health risks for city residents.
In an analysis of 65 cities across North America, researchers found that variation in how efficiently urban areas release heat back into the lower atmosphere — through the process of convection — is the dominant factor in the daytime UHI effect. This finding challenges a long-held belief that the phenomenon is driven principally by diminished evaporative cooling through the loss of vegetation.
The effects of impaired "convective efficiency" are particularly acute in wet climates, the researchers say. In cities such as Atlanta, Georgia, and Nashville, Tennessee, this factor alone contributes a 3-degree C rise in average daytime temperatures, according to the study, published July 10 in the journal Nature.
The phenomenon could have profound impacts on human health in cities worldwide as mean global temperatures continue to rise — and as more and more people move into cities — said Xuhui Lee, the Sara Shallenberger Brown Professor of Meteorology at the Yale School of Forestry & Environmental Studies (F&ES) and one of the study's authors.
"There is a synergistic relationship between climate conditions and the urban heat island," Lee said. "This relationship suggests that the urban heat island will exacerbate heat wave stress on human health in wet climates where temperature effects are already compounded by high humidity.
"This is a huge concern from a public health perspective."
For years scientists have recognized the primary causes of the UHI effect. In addition to the changes in convection efficiency and evaporative cooling, these include the tendency of buildings, pavement, and other structures to store more heat than vegetation and soil; heat generated by human-built industrial systems; and changes to the albedo of the Earth's surface. (Albedo refers to the proportion of sunlight or radiation reflected by the surface of the planet. Light-colored parking lots, for instance, reflect more sunlight back into space than darker surfaces.)
Using satellite data of land surface temperatures and vegetation cover from cities in the United States and Canada, researchers calculated the mean temperature differentials between urban centers and their rural surroundings during both daytime and nighttime hours. They also used climate modeling to produce a more complex range of variables — from air density to aerodynamic resistance — which were then used to quantify the roles of each of the primary drivers of UHI (radiation, convection, evaporation, heat storage, and human-generated heat).
Their results reaffirmed the consensus view that, regardless of the local climate, the release of heat stored in human-built structures is the dominant contributor to UHI during the nighttime.
But during the daytime, researchers found, convection is the dominant factor — particularly in "wetter" cities of the southeastern United States. In those places, the smooth surfaces of buildings and other human-made features are far less conducive to heat diffusion than the densely vegetated areas that surround them. Overall, in wetter climates urbanization reduces convection efficiency by 58 percent.
"The 'rougher' surfaces of the vegetation triggers turbulence, and turbulence removes heat from the surface to the atmosphere," said Lei Zhao, a doctoral student at F&ES and lead author of the study. "But where there is a smoother surface, there is less convection and the heat will be trapped in the surface."
Convection plays a key role in drier cities, too — albeit with far different consequences. In those settings — including in urban areas of the U.S. Southwest where surrounding vegetation is typically shorter and scrubbier — the rural areas are less effective at dissipating heat. As a result, the urban landscapes are actually 20 percent more efficient in removing heat than their rural surroundings, triggering a 1.5-degree C cooling within the cities.
### Other authors of the paper, "Strong contributions of local background climate to urban heat island," are Ronald B. Smith of the Yale Department of Geology and Geophysics, and Keith Oleson of the U.S. National Center for Atmospheric Research.
Strong contributions of local background climate to urban heat islands
Lei Zhao, Xuhui Lee, Ronald B. Smith & Keith Oleson
Nature511, 216–219 (10 July 2014) doi:10.1038/nature13462 Received 19 January 2014 Accepted 07 May 2014 Published online 09 July 2014
The urban heat island (UHI), a common phenomenon in which surface temperatures are higher in urban areas than in surrounding rural areas, represents one of the most significant human-induced changes to Earth’s surface climate1,2. Even though they are localized hotspots in the landscape, UHIs have a profound impact on the lives of urban residents, who comprise more than half of the world’s population3. A barrier to UHI mitigation is the lack of quantitative attribution of the various contributions to UHI intensity4 (expressed as the temperature difference between urban and rural areas, ΔT). A common perception is that reduction in evaporative cooling in urban land is the dominant driver of ΔT (ref. 5). Here we use a climate model to show that, for cities across North America, geographic variations in daytime ΔT are largely explained by variations in the efficiency with which urban and rural areas convect heat to the lower atmosphere. If urban areas are aerodynamically smoother than surrounding rural areas, urban heat dissipation is relatively less efficient and urban warming occurs (and vice versa). This convection effect depends on the local background climate, increasing daytime ΔT by 3.0 ± 0.3 kelvin (mean and standard error) in humid climates but decreasing ΔT by 1.5 ± 0.2 kelvin in dry climates. In the humid eastern United States, there is evidence of higher ΔT in drier years. These relationships imply that UHIs will exacerbate heatwave stress on human health in wet climates where high temperature effects are already compounded by high air humidity6, 7 and in drier years when positive temperature anomalies may be reinforced by a precipitation–temperature feedback8. Our results support albedo management as a viable means of reducing ΔT on large scales9, 10.