PNAS highlights for the week of May 9 - 13


Assessing Image Quality in Fingerprint Identification

A newly published mathematical model suggests that the United States government could increase its chances of catching known criminals at ports of entry by adjusting its biometric identification system to compensate for varying fingerprint image quality.

Visitors now provide two index-finger fingerprints upon arrival, which are compared with database images from a watchlist of about 6 million criminals and suspected terrorists.

Lawrence Wein and Manas Baveja explored two alternative identification systems by using published fingerprint data together with a mathematical model that accounts for difficulties in matching poor-quality images.

The authors' model suggests that under existing policies, the probability of the current system matching an illegal visitor's poor-quality prints to the correct database prints is 52.6%. If the requirement for a match under these conditions is allowed to vary with image quality, however, the model predicts a detection probability of 73.3%. If more than two fingerprints can be used to match visitors with poor image quality, the detection probability increases to 94.9%.

The authors' model may thus address situations where individuals have fingerprints of poor image quality--for example, those deliberately altered through surgery, chemicals, or abrasion.

Land Use Impacts Earth's Water Balance

Human modification of Earth's water cycle through deforestation and irrigation may have significant regional impact on weather patterns and food production, researchers report.

While agricultural practices are known to alter liquid water flow across Earth's surface, human-induced alteration of water vapor flow has received considerably less attention.

By comparing current land use patterns with Earth's pre-human vegetation cover, Line Gordon and colleagues estimated global vapor flow changes due to deforestation and irrigation, since the start of human-induced land use change.

The researchers estimated global water vapor flow from land at 67,000 km3/year. Deforestation has led to a 3,000 km3/year decrease in water vapor flow, while irrigation has caused an almost equivalent increase.

On a global scale, decreases in water vapor flow due to deforestation cancel out increased flow associated with irrigation. However, the spatial pattern of water vapor flow has changed substantially, leading to major regional effects obscured in global estimates. In areas where increased food production leads to both widespread deforestation and irrigation, as in the Indian Ocean basin, the change in vapor flow may trigger disruptions of the Asian monsoon system.

The researchers suggest that such land use changes need to be considered when developing climate models.

Potential Pheromone Activates Brains of Homosexual Men

A potential pheromone found in male perspiration activates the brains of homosexual men and heterosexual women in a similar manner, researchers report.

While it is unclear if humans respond to pheromones, candidate compounds include a testosterone derivative called 4,16-androstadien-3-one (AND), and the estrogen-like steroid estra-1,3-5(10),16-tetraen-3-ol (EST).

In a previous study, Ivanka Savic and colleagues demonstrated that the hypothalamus region of the brain becomes activated when men smell EST and women smell AND, but not vice versa.

In the current study, the researchers examined whether brain activation patterns induced by EST and AND corresponded with sexual orientation, rather than with biological gender. The scientists compared brain activity between homosexual men, and heterosexual men and women, in response to smelling EST, AND, and ordinary odors, such as lavender.

The researchers observed that AND activated the hypothalamus in homosexual men and heterosexual women, but not heterosexual men. Conversely, EST activated the hypothalamus in heterosexual men alone. All three groups responded to common odors similarly, engaging only brain regions that process smell.

These findings indicate that the human brain reacts differently to these potential pheromones compared with common odors, suggesting a link between sexual orientation and brain function.

Women Migrate More than Men, Based on Society

A newly published study shows that immigration rates differ between genders and follow societal rules, with women moving more often than men overall.

Laurent Excoffier and colleagues analyzed previously published genetic data with a statistical method that allows estimation of male- and female-specific migration rates.

The study focused on two kinds of societies in Northern Thailand. In patrilocal societies, a woman moves to the village of her new husband. In matrilocal societies, a man moves to the village of his new wife.

The researchers examined how this dispersal of the sexes affects the gene pool of the different populations. They studied mitochondrial DNA and genes from the Y chromosome, sex-specific tracers of females and males, respectively, from three matrilocal and three patrilocal populations. The analysis provided the rate of sex-specific immigration into the different societies.

Interestingly, men and women moved at about the same rate within matrilocal societies, but women moved far more than men in patrilocal groups.

The results suggest that while men are strictly controlling immigration in traditional patrilocal populations, the process is much less regulated in matrilocal communities. The results further suggest that genetic analysis can give insight into human social structure.

Blood Test for Ovarian Cancer

Researchers have developed a blood screening test that could help catch ovarian cancer in its early stages, when few symptoms are present.

Ovarian cancer, the leading cause of gynecologic cancer deaths in the U.S. and 3 times more lethal than breast cancer, is usually not diagnosed until its advanced stages. Clinicians currently have no sensitive screening method because the disease shows few symptoms in its early stages.

David Ward and colleagues developed and tested a blood test for ovarian cancer based on four proteins: leptin, prolactin, osteopontin, and insulin-like growth factor-II. If the level of two or more of these biomarkers for a patient falls within a certain range, the test will predict that a tumor is present. In a test group of more than 200 healthy women and women with ovarian cancer, the test showed 95% sensitivity (fraction correctly diagnosed with cancer) and 95% specificity (fraction correctly diagnosed as cancer-free). Each of the proteins had been previously suggested as an accurate cancer biomarker, though not as a set. In this study, no single protein could completely distinguish the cancer patients from healthy control individuals.


Intestinal Neuropeptides Control GI Inflammation

Researchers report that the neuropeptides corticotropin-releasing factor (CRF) and urocortin II (UcnII) are synthesized in the small intestine to regulate inflammation, shedding light on diseases such as irritable bowel syndrome.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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