Electric‐field dependence of acceptor‐level binding energies in strained SiGe and InGaAs quantum‐well structures

The acceptor energies for strained SiGe (on Si) and InGaAs (on GaAs) quantum wells are calculated from a 4×4 k⋅p band structure that includes the effects of strain and electric fields. Both center‐ and edge‐doped cases are examined. The theory shows marked changes in the acceptor energies with both strain and electric field. The wide variation in binding energy for the edge‐doped quantum wells may provide a mechanism for tunable far‐infrared detectors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70960/2/JAPIAU-71-4-2023-1.pd

Self sacrifice and kin psychology in war : threats to family predict decisions to volunteer for a women's paramilitary organization

The conditions that propel humans to make sacrifices for groups of unrelated, and often unknown, individualshas received considerable attention across scientific disciplines. Evolutionary explanations for this type of sa-crifice have focused on how men form strategic coalitions organized around kin networks and reciprocity whenfaced with out-group threats. Few studies, however, have analyzed how women respond to external threats.Using data from one of the largest female paramilitary organizations in history we show that women who havemore brothers, women whose husbands serve in the military and women without children are more likely tovolunteer. These results provide qualified support for the hypothesis that women are more likely to sacrifice fortheir country when members of their family are at risk. Overall, our analysis suggests that self-sacrifice andintense bonding with an imagined community of unknown individuals, such as the nation state, may arise out ofa suite of psychological adaptations designed to facilitate cooperation among kin (i.e. kin psychology). Theseresults can be interpreted within the framework of kin selection showing how individuals come to view un-related group members as family. They may also shed light on various theories of group alignment, such as‘identity fusion’–whereby individuals align their personal identity and interests with those of the group–and onour understanding of evolutionary adaptations that cause women to direct altruism toward in-groups.Peer reviewe

Comparison of mode suppression and large signal modulation between lattice matched and strained InGaAs/AlGaAs quantum well lasers

Numerical techniques are developed to study the output spectra and to solve the coupled mode rate equations for InxGa1−xAs/Al0.3Ga0.7As quantum well lasers. The optical properties of the laser are calculated from a 4×4 k⋅p band structure which includes the effects of strain. We find that the side modes are severely suppressed in the strained laser. Large signal switching of the laser is also studied and the role of strain is identified in the device response. If the laser is switched from the off state to a state of given photon density in the lasing mode, then the strained system exhibits a faster time response. If, however, the laser is switched from the off state to a state of given total photon density, then the strained system has a slower time response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70732/2/APPLAB-59-19-2381-1.pd

Child volunteers in a women’s paramilitary organization in World War II have accelerated reproductive schedules.

Understanding how conditions experienced during development affect reproductive timing is of considerable cross-disciplinary interest. Life-history theory predicts that organisms will accelerate reproduction when future survival is unsure. In humans, this can be triggered by early exposure to mortality. Previous studies, however, have been inconclusive due to several confounds that are also likely to affect reproduction. Here we take advantage of a natural experiment in which a population is temporarily divided by war to analyze how exposure to mortality affects reproduction. Using records of Finnish women in World War II, we find that young girls serving in a paramilitary organization wait less time to reproduce, have shorter inter-birth intervals, and have more children than their non-serving peers or sisters. These results support the hypothesis that exposure to elevated mortality rates during development can result in accelerated reproductive schedules and adds to our understanding of how participation in warfare affects women.Peer reviewe

Selective Fatty Acid Retention and Turnover in the Freshwater Amphipod Pallaseopsis quadrispinosa

Gammarid amphipods are a crucial link connecting primary producers with secondary consumers, but little is known about their nutritional ecology. Here we asked how starvation and subsequent feeding on different nutritional quality algae influences fatty acid retention, compound-specific isotopic carbon fractionation, and biosynthesis of ω-3 and ω-6 polyunsaturated fatty acids (PUFA) in the relict gammarid amphipod Pallaseopsis quadrispinosa. The fatty acid profiles of P. quadrispinosa closely matched with those of the dietary green algae after only seven days of refeeding, whereas fatty acid patterns of P. quadrispinosa were less consistent with those of the diatom diet. This was mainly due to P. quadrispinosa suffering energy limitation in the diatom treatment which initiated the metabolization of 16:1ω7 and partly 18:1ω9 for energy, but retained high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) similar to those found in wild-caught organisms. Moreover, α-linolenic acid (ALA) from green algae was mainly stored and not allocated to membranes at high levels nor biosynthesized to EPA. The arachidonic acid (ARA) content in membrane was much lower than EPA and P. quadrispinosa was able to biosynthesize long-chain ω-6 PUFA from linoleic acid (LA). Our experiment revealed that diet quality has a great impact on fatty acid biosynthesis, retention and turnover in this consumer

Selective Fatty Acid Retention and Turnover in the Freshwater Amphipod Pallaseopsis quadrispinosa

Gammarid amphipods are a crucial link connecting primary producers with secondary consumers, but little is known about their nutritional ecology. Here we asked how starvation and subsequent feeding on different nutritional quality algae influences fatty acid retention, compound-specific isotopic carbon fractionation, and biosynthesis of ω-3 and ω-6 polyunsaturated fatty acids (PUFA) in the relict gammarid amphipod Pallaseopsis quadrispinosa. The fatty acid profiles of P. quadrispinosa closely matched with those of the dietary green algae after only seven days of refeeding, whereas fatty acid patterns of P. quadrispinosa were less consistent with those of the diatom diet. This was mainly due to P. quadrispinosa suffering energy limitation in the diatom treatment which initiated the metabolization of 16:1ω7 and partly 18:1ω9 for energy, but retained high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) similar to those found in wild-caught organisms. Moreover, α-linolenic acid (ALA) from green algae was mainly stored and not allocated to membranes at high levels nor biosynthesized to EPA. The arachidonic acid (ARA) content in membrane was much lower than EPA and P. quadrispinosa was able to biosynthesize long-chain ω-6 PUFA from linoleic acid (LA). Our experiment revealed that diet quality has a great impact on fatty acid biosynthesis, retention and turnover in this consumer

Socio-cultural similarity with host population rather than ecological similarity predicts success and failure of human migrations

Demographers argue that human migration patterns are shaped by people moving to better environments. More recently, however, evolutionary theorists have argued that people move to similar environments to which they are culturally adapted. While previous studies analysing which factors affect migration patterns have focused almost exclusively on successful migrations, here we take advantage of a natural experiment during World War II in which an entire population was forcibly displaced but were then allowed to return home to compare successful with unsuccessful migrations. We test two competing hypotheses: (1) individuals who relocate to environments that are superior to their place of origin will be more likely to remain-The Better Environment Hypothesis or (2) individuals who relocate to environments that are similar to their place of origin will be more likely to remain-The Similar Environment Hypothesis. Using detailed records recording the social, cultural, linguistic and ecological conditions of the origin and destination locations, we find that cultural similarity (e.g. linguistic similarity and marrying within one's own minority ethnic group)-rather than ecological differences-are the best predictors of successful migrations. These results suggest that social relationships, empowered by cultural similarity with the host population, play a critical role in successful migrations and provide limited support for the similar environment hypothesis. Overall, these results demonstrate the importance of comparing unsuccessful with successful migrations in efforts understand the engines of human dispersal and suggest that the primary obstacles to human migrations and successful range expansion are sociocultural rather than ecological.Peer reviewe

External Load Affects Ground Reaction Force Parameters Non-uniformly during Running in Weightlessness

Long-term exposure to microgravity induces detrimefits to the musculcskdetal system (Schneider et al., 1995; LeBlanc et al., 2000). Treadmill exercise is used onboard the International Space Station as an exercise countermeasure to musculoskeletal deconditioning due to spaceflight. During locomotive exercise in weightlessness (0G), crewmembers wear a harness attached to an external loading mechanism (EL). The EL pulls the crewmember toward the treadmill, and provides resistive load during the impact and propulsive phases of gait. The resulting forces may be important in stimulating bone maintenance (Turner, 1998). The EL can be applied via a bungee and carabineer clip configuration attached to the harness and can be manipulated to create varying amounts of load levels during exercise. Ground-based research performed using a vertically mounted treadmill found that peak ground reaction forces (GRF) during running at an EL of less than one body weight (BW) are less than those that occur during running in normal gravity (1G) (Davis et al., 1996). However, it is not known how the GRF are affected by the EL in a true OG environment. Locomotion while suspended may result in biomechanics that differ from free running. The purpose of this investigation was to determine how EL affects peak impact force, peak propulsive force, loading rate, and impulse of the GRF during running in 0G. It was hypothesized that increasing EL would result in increases in each GRF parameter