Showing papers by "University of California, Davis published in 2001"

Historical overfishing and the recent collapse of coastal ecosystems.

Abstract: Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.

Boys will be Boys: Gender, Overconfidence, and Common Stock Investment

Abstract: Theoretical models predict that overconedent investors trade excessively We test this prediction by partitioning investors on gender Psychological research demonstrates that, in areas such as enance, men are more overconedent than women Thus, theory predicts that men will trade more excessively than women Using account data for over 35,000 households from a large discount brokerage, we analyze the common stock investments of men and women from February 1991 through January 1997 We document that men trade 45 percent more than women Trading reduces men’s net returns by 265 percentage points a year as opposed to 172 percentage points for women It’s not what a man don’t know that makes him a fool, but what he does know that ain’t so Josh Billings, nineteenth century American humorist It is difecult to reconcile the volume of trading observed in equity markets with the trading needs of rational investors Rational investors make periodic contributions and withdrawals from their investment portfolios, rebalance their portfolios, and trade to minimize their taxes Those possessed of superior information may trade speculatively, although rational speculative traders will generally not choose to trade with each other It is unlikely that rational trading needs account for a turnover rate of

Measuring Global Self-Esteem: Construct Validation of a Single-Item Measure and the Rosenberg Self-Esteem Scale

Abstract: Four studies examined the construct validity of two global self-esteem measures. In Studies 1 through 3, the Single-Item Self-Esteem Scale (SISE) and the Rosenberg Self-Esteem Scale (RSE) showed strong convergent validity for men and women, for different ethnic groups, and for both college students and community members. The SISE and the RSE had nearly identical correlations with a wide range of criterion measures, including domain-specific self-evaluations, self-evaluative biases, social desirability, personality, psychological and physical health, peer ratings of group behavior, academic outcomes, and demographic variables. Study 4 showed that the SISE had only moderate convergent validity in a sample of children. Overall, the findings support the reliability and validity of the SISE and suggest it can provide a practical alternative to the RSE in adult samples. More generally, the findings contribute to the research literature by further elaborating the nomological network of global self-esteem.

Variation in δ15N and δ13C trophic fractionation: Implications for aquatic food web studies

Abstract: Use of stable isotope techniques to quantify food web relationships requires a priori estimates of the enrichment or depletion in δ15N and δ13C values between prey and predator (known as trophic fractionation; hereafter Δδ15N and Δδ13C). We conducted a broad-scale analysis of Δδ15N and Δδ13C from aquatic systems, including three new field estimates. Carnivores had significantly higher Δδ15N values than herbivores. Furthermore, carnivores, invertebrates, and lab-derived estimates were significantly more variable than their counterparts ( f-test, p < 0.00001). Δδ13C was higher for carnivores than for herbivores (p = 0.001), while variances did not differ significantly. Excluding herbivores, the average Δδ15N and Δδ13C were 3.4‰ and 0.8‰, respectively. But even with unbiased fractionation estimates, there is variation in isotopic fractionation that contributes to error in quantitative isotope model outputs. We simulated the error variance in δ15N-based estimates of trophic position and two-source δ13C diet mixing models, explicitly considering the observed variation in Δδ15N and Δδ13C, along with the other potential error sources. The resultant error in trophic position and mixing model outputs was generally minor, provided that primary consumers were used as baseline indicators for estimating trophic position and that end member d13C values in dietary mixing models were sufficiently distinct.

Low-density parity-check codes based on finite geometries: a rediscovery and new results

Abstract: This paper presents a geometric approach to the construction of low-density parity-check (LDPC) codes. Four classes of LDPC codes are constructed based on the lines and points of Euclidean and projective geometries over finite fields. Codes of these four classes have good minimum distances and their Tanner (1981) graphs have girth 6. Finite-geometry LDPC codes can be decoded in various ways, ranging from low to high decoding complexity and from reasonably good to very good performance. They perform very well with iterative decoding. Furthermore, they can be put in either cyclic or quasi-cyclic form. Consequently, their encoding can be achieved in linear time and implemented with simple feedback shift registers. This advantage is not shared by other LDPC codes in general and is important in practice. Finite-geometry LDPC codes can be extended and shortened in various ways to obtain other good LDPC codes. Several techniques of extension and shortening are presented. Long extended finite-geometry LDPC codes have been constructed and they achieve a performance only a few tenths of a decibel away from the Shannon theoretical limit with iterative decoding.

Sequence-related amplified polymorphism (SRAP), a new marker system based on a simple PCR reaction: its application to mapping and gene tagging in Brassica

Abstract: We developed a simple marker technique called sequence-related amplified polymorphism (SRAP) aimed for the amplification of open reading frames (ORFs). It is based on two-primer amplification. The primers are 17 or 18 nucleotides long and consist of the following elements. Core sequences, which are 13 to 14 bases long, where the first 10 or 11 bases starting at the 5′ end, are sequences of no specific constitution (”filler” sequences), followed by the sequence CCGG in the forward primer and AATT in the reverse primer. The core is followed by three selective nucleotides at the 3′ end. The filler sequences of the forward and reverse primers must be different from each other and can be 10 or 11 bases long. For the first five cycles the annealing temperature is set at 35°C. The following 35 cycles are run at 50°C. The amplified DNA fragments are separated by denaturing acrylamide gels and detected by autoradiography. We tested the marker technique in a series of recombinant inbred and doubled-haploid lines of Brassica oleracea L. After sequencing, approximately 45% of the gel-isolated bands matched known genes in the Genbank database. Twenty percent of the SRAP markers were co-dominant, which was demonstrated by sequencing. Construction of a linkage map revealed an even distribution of the SRAP markers in nine major linkage groups, not differing in this regard to AFLP markers. We successfully tagged the glucosinolate desaturation gene BoGLS-ALK with these markers. SRAPs were also easily amplified in other crops such as potato, rice, lettuce, Chinese cabbage (Brassica rapa L.), rapeseed (Brassica napus L.), garlic, apple, citrus, and celery. We also amplified cDNA isolated from different tissues of Chinese cabbage, allowing the fingerprinting of these sequences.

Lack of effect of induction of hypothermia after acute brain injury.

Abstract: Background Induction of hypothermia in patients with brain injury was shown to improve outcomes in small clinical studies, but the results were not definitive. To study this issue, we conducted a multicenter trial comparing the effects of hypothermia with those of normothermia in patients with acute brain injury. Methods The study subjects were 392 patients 16 to 65 years of age with coma after sustaining closed head injuries who were randomly assigned to be treated with hypothermia (body temperature, 33°C), which was initiated within 6 hours after injury and maintained for 48 hours by means of surface cooling, or normothermia. All patients otherwise received standard treatment. The primary outcome measure was functional status six months after the injury. Results The mean age of the patients and the type and severity of injury in the two treatment groups were similar. The mean (±SD) time from injury to randomization was 4.3±1.1 hours in the hypothermia group and 4.1±1.2 hours in the normothermia group, a...

Is gratitude a moral affect

Abstract: Gratitude is conceptualized as a moral affect that is analogous to other moral emotions such as empathy and guilt. Gratitude has 3 functions that can be conceptualized as morally relevant: (a) a moral barometer function (i.e., it is a response to the perception that one has been the beneficiary of another person's moral actions); (b) a moral motive function (i.e., it motivates the grateful person to behave prosocially toward the benefactor and other people); and (c) a moral reinforcer function (i.e., when expressed, it encourages benefactors to behave morally in the future). The personality and social factors that are associated with gratitude are also consistent with a conceptualization of gratitude as an affect that is relevant to people's cognitions and behaviors in the moral domain.

When Innovations Meet Institutions: Edison and the Design of the Electric Light:

Abstract: This paper considers the role of design, as the emergent arrangement of concrete details that embodies a new idea, in mediating between innovations and established institutional fields as entrepren...

Learning to Be Overconfident

Abstract: We develop a multiperiod market model describing both the process by which traders learn about their ability and how a bias in this learning can create overconfident traders. A trader in our model initially does not know his own ability. He infers this ability from his successes and failures. In assessing his ability the trader takes too much credit for his successes. This leads him to become overconfident. A trader’s expected level of overconfidence increases in the early stages of his career. Then, with more experience, he comes to better recognize his own ability. The patterns in trading volume, expected profits, price volatility, and expected prices resulting from this endogenous overconfidence are analyzed.

Sperm Morphology, Motility, and Concentration in Fertile and Infertile Men

Abstract: Background Although semen analysis is routinely used to evaluate the male partner in infertile couples, sperm measurements that discriminate between fertile and infertile men are not well defined. Methods We evaluated two semen specimens from each of the male partners in 765 infertile couples and 696 fertile couples at nine sites. The female partners in the infertile couples had normal results on fertility evaluation. The sperm concentration and motility were determined at the sites; semen smears were stained at the sites and shipped to a central laboratory for an assessment of morphologic features of sperm with the use of strict criteria. We used classification-and-regression-tree analysis to estimate threshold values for subfertility and fertility with respect to the sperm concentration, motility, and morphology. We also used an analysis of receiver-operating-characteristic curves to assess the relative value of these sperm measurements in discriminating between fertile and infertile men. Results The su...

Transgenic salt-tolerant tomato plants accumulate salt in foliage but not in fruit

Abstract: ++ antiport were able to grow, flower, and produce fruit in the presence of 200 mM sodium chloride. Although the leaves accumulated high sodium concentrations, the tomato fruit displayed very low sodium content. Contrary to the notion that multiple traits introduced by breeding into crop plants are needed to obtain salt-tolerant plants, the modification of a single trait significantly improved the salinity tolerance of this crop plant. These results demonstrate that with a combination of breeding and transgenic plants it could be possible to produce salt-tolerant crops with far fewer target traits than had been anticipated. The accumulation of sodium in the leaves and not in the fruit demonstrates the utility of such a modification in preserving the quality of the fruit. RESEARCH ARTICLE Agricultural productivity is severely affected by soil salinity, and the damaging effects of salt accumulation in agricultural soils have influenced ancient and modern civilizations. Much research is aimed toward the breeding of crop cultivars with improved salt tolerance. One school of thought has concluded that salt tolerance will be achieved only after pyramiding several characteristics in a single genotype, whereas each one alone could not confer a significant increase in salt tolerance 1,2 . Arguably, salt tolerance is a complex trait, and the long list of salt stress-responsive genes seems to support this 3 . However, the overexpression of a single gene recently was shown to improve salt tolerance in Arabidopsis 4 . The detrimental effects of salt on plants are a consequence of both a water deficit resulting in osmotic stress and the effects of excess sodium ions on key biochemical processes. To tolerate high levels of salts, plants should be able to use ions for osmotic adjustment and to internally distribute these ions to keep sodium away from the cytosol. The presence of large, acidic-inside, membranebound vacuoles in plant cells allows the efficient compartmentation of sodium into the vacuole through the operation of vacuolar Na

Role of PHABULOSA and PHAVOLUTA in determining radial patterning in shoots

Abstract: The upper side of the angiosperm leaf is specialized for efficient capture of sunlight whereas the lower side is specialized for gas exchange. In Arabidopsis, the establishment of polarity in the leaf probably requires the generation and perception of positional information along the radial (adaxial versus abaxial or central versus peripheral) dimension of the plant. This is because the future upper (adaxial) side of the leaf develops from cells closer to the centre of the shoot, whereas the future under (abaxial) side develops from cells located more peripherally. Here we implicate the Arabidopsis PHABULOSA and PHAVOLUTA genes in the perception of radial positional information in the leaf primordium. Dominant phabulosa (phb) and phavoluta (phv) mutations cause a dramatic transformation of abaxial leaf fates into adaxial leaf fates. They do so by altering the predicted sterol/lipid-binding domains of ATHB14 and ATHB9, proteins of previously unknown function that also contain DNA-binding motifs. This change probably renders the protein constitutively active, implicating this domain as a central regulator of protein function and the PHB and PHV proteins as receptors for an adaxializing signal.

Laparoscopic Versus Open Gastric Bypass: A Randomized Study of Outcomes, Quality of Life, and Costs

Abstract: Objective To compare outcomes, quality of life (QOL), and costs of laparoscopic and open gastric bypass (GBP). Background Data Laparoscopic GBP has been reported to be a safe and effective approach for the treatment of morbid obesity. The authors performed a prospective randomized trial to compare outcomes, QOL, and costs of laparoscopic GBP with those of open GBP. Methods From May 1999 to March 2001, 155 patients with a body mass index (BMI) of 40 to 60 kg/m 2 were randomly assigned to undergo laparoscopic (n = 79) or open (n = 76) GBP. The two groups were similar in age, sex ratio, mean BMI, and comorbidities. Main outcome measures included operative time, estimated blood loss, length of hospital stay, operative complications, percentage of excess body weight loss, and time to return to activities of daily living and work. Changes in QOL were assessed using the SF-36 Health Survey and the bariatric analysis of reporting outcome system (BAROS). Operative and hospital costs of the two operations were also compared. Results There were no deaths in either group. Mean operative time was longer for laparoscopic GBP than for open GBP, but operative blood loss was less. Two (2.5%) of the 79 patients in the laparoscopic group required conversion to laparotomy. Median length of hospital stay was shorter for laparoscopic GBP patients (3 vs 4 days). The rate of postoperative anastomotic leak was similar between groups. Wound-related complications such as infection (10.5 vs 1.3%) and incisional hernia (7.9 vs 0%) were more common after open GBP; late anastomotic stricture was less frequent after open GBP (2.6 vs 11.4%). Time to return to activities of daily living and work were shorter after laparoscopic GBP than after open GBP. Weight loss at 1 year was similar between groups. Preoperative SF-36 scores were similar between groups; however, at 1 month after surgery, laparoscopic patients had better physical conditioning, social functioning, general health, and less body pain than open GBP patients. At 6 months, the BAROS outcome was classified as good or better in 97% of laparoscopic GBP patients compared with 82% of open GBP patients. Operative costs were higher for laparoscopic GBP patients, but hospital costs were lower. Conclusions Laparoscopic GBP is a safe and cost-effective alternative to open GBP. Despite a longer operative time, patients undergoing laparoscopic GBP benefited from less blood loss, a shorter hospital stay, and faster convalescence. Laparoscopic GBP patients had comparable weight loss at 1 year but a more rapid improvement in QOL than open GBP patients. The higher initial operative costs for laparoscopic GBP were adequately offset by the lower hospital costs.

The CIPIC HRTF database

Abstract: This paper describes a public-domain database of high-spatial-resolution head-related transfer functions measured at the UC Davis CIPIC Interface Laboratory and the methods used to collect the data.. Release 1.0 (see http://interface.cipic.ucdavis.edu) includes head-related impulse responses for 45 subjects at 25 different azimuths and 50 different elevations (1250 directions) at approximately 5/spl deg/ angular increments. In addition, the database contains anthropometric measurements for each subject. Statistics of anthropometric parameters and correlations between anthropometry and some temporal and spectral features of the HRTFs are reported.

Acid fumigation of soils to remove carbonates prior to total organic carbon or CARBON-13 isotopic analysis

Abstract: The use of 13 C natural abundance (δ 13 C) to follow C input to soil has gained widespread acceptance. However, inorganic C present in the soil as carbonates will interfere with the measurement of soil organic 13 C unless removed or excluded from measurement. We report a simple and convenient HCl-fumigation method to remove inorganic C from soil. Soil samples are weighed in Ag-foil capsules, arranged on a microtiter plate, wetted with water to approximately field capacity, and placed in a desiccator containing a beaker with concentrated (12 M) HCl. The carbonates are released as CO 2 by the acid treatment in 6 to 8 h. The soil samples are then dried at 60°C prior to isotope determination. The advantages of the HCl-fumigation method to remove inorganic C from the soil are that: (i) no water soluble C will be lost from the soil; (ii) a large number of samples can be processed simultaneously; (iii) the removal of inorganic C is rapid and complete; and (iv) the method could also be used to determine both organic and inorganic C content in the soil. A potential disadvantage, however, is that the HCl fumigation changed the 15 N natural abundance of soil N.

Theory and speciation

Abstract: The study of speciation has become one of the most active areas of evolutionary biology, and substantial progress has been made in documenting and understanding phenomena ranging from sympatric speciation and reinforcement to the evolutionary genetics of postzygotic isolation. This progress has been driven largely by empirical results, and most useful theoretical work has concentrated on making sense of empirical patterns. Given the complexity of speciation, mathematical theory is subordinate to verbal theory and generalizations about data. Nevertheless, mathematical theory can provide a useful classification of verbal theories; can help determine the biological plausibility of verbal theories; can determine whether alternative mechanisms of speciation are consistent with empirical patterns; and can occasionally provide predictions that go beyond empirical generalizations. We discuss recent examples of progress in each of these areas.

A Survey of z > 5.8 quasars in the Sloan Digital Sky Survey I: Discovery of three new quasars and the spatial density of luminous quasars at z ~ 6

Abstract: We present the results from a survey of i-dropout objects selected from ~1550 deg2 of multicolor imaging data from the Sloan Digital Sky Survey to search for luminous quasars at z 5.8. Objects with i*-z* > 2.2 and z* 0.90. The ARC 3.5 m spectrum of SDSSp J103027.10+052455.0 shows that over a range of ~300 A immediately blueward of the Lyα emission, the average transmitted flux is only 0.003 ± 0.020 times that of the continuum level, consistent with zero flux over a ~300 A range of the Lyα forest region and suggesting a tentative detection of the complete Gunn-Peterson trough. The existence of strong metal lines in the quasar spectra suggests early metal enrichment in the quasar environment. The three new objects, together with the previously published z = 5.8 quasar SDSSp J104433.04-012502.2, form a complete color-selected flux-limited sample at z 5.8. We estimate the selection function of this sample, taking into account the estimated variations in the quasar spectral energy distribution, as well as observational photometric errors. We find that at z = 6, the comoving density of luminous quasars at M1450 < -26.8 (H0 = 50 km s-1 Mpc-1, Ω = 1) is 1.1 × 10-9 Mpc-3. This is a factor of ~2 lower than that at z ~ 5 and is consistent with an extrapolation of the observed quasar evolution at z < 5. Using the current sample, we discuss the constraint on the shape of the quasar luminosity function and the implications for the contribution of quasars to the ionizing background at z ~ 6. The luminous quasars discussed in the paper have central black hole masses of several times 109 M⊙ by the Eddington argument, with likely dark halo masses on the order of 1013 M⊙. Their observed space density provides a sensitive test of models of quasar and galaxy formation at high redshift.

Evidence for reionization at z ∼ 6: Detection of a gunn-peterson trough in a z = 6.28 quasar

Abstract: We present moderate-resolution Keck spectroscopy of quasars at z = 5.82, 5.99, and 6.28, discovered by the Sloan Digital Sky Survey (SDSS). We find that the Ly? absorption in the spectra of these quasars evolves strongly with redshift. To z ~ 5.7, the Ly? absorption evolves as expected from an extrapolation from lower redshifts. However, in the highest-redshift object, SDSSp J103027.10+052455.0 (z = 6.28), the average transmitted flux is 0.0038 ? 0.0026 times that of the continuum level over 8450 ? 20, on the optical depth to Ly? absorption at z = 6. This is a clear detection of a complete Gunn-Peterson trough, caused by neutral hydrogen in the intergalactic medium. Even a small neutral hydrogen fraction in the intergalactic medium would result in an undetectable flux in the Ly? forest region. Therefore, the existence of the Gunn-Peterson trough by itself does not indicate that the quasar is observed prior to the reionization epoch. However, the fast evolution of the mean absorption in these high-redshift quasars suggests that the mean ionizing background along the line of sight to this quasar has declined significantly from z ~ 5 to 6, and the universe is approaching the reionization epoch at z ~ 6.

Journeys from Childhood to Midlife: Risk, Resilience, and Recovery

Abstract: The latest report from the Kauai Longitudinal Study addresses 2 fundamental questions of interest to pediatricians and health care professionals: 1) What are the long-term effects of adverse perinatal and early child-rearing conditions on individuals’ physical, cognitive, and psychosocial development at midlife? 2) Which protective factors allow most individuals who are exposed to multiple childhood risk factors to make a successful adaptation in adulthood?1 The Kauai Longitudinal Study has monitored the impact of a wide array of biological, psychological, and social risk factors on the lives of a multiracial cohort of 698 individuals who were born in 1955 on the Hawaiian island of Kauai, from the perinatal … Reprint requests to (E.E.W.) Department of Human and Community Development, University of California, Davis, CA 95616. E-mail: eewerner{at}ucdavis.edu

Absolute diversification rates in angiosperm clades

Abstract: The extraordinary contemporary species richness and ecological predominance of flowering plants (angiosperms) are even more remarkable when considering the relatively recent onset of their evolutionary diversification. We examine the evolutionary diversification of angiosperms and the observed differential distribution of species in angiosperm clades by estimating the rate of diversification for angiosperms as a whole and for a large set of angiosperm clades. We also identify angiosperm clades with a standing diversity that is either much higher or lower than expected, given the estimated background diversification rate. Recognition of angiosperm clades, the phylogenetic relationships among them, and their taxonomic composition are based on an empirical compilation of primary phylogenetic studies. By making an integrative and critical use of the paleobotanical record, we obtain reasonably secure approximations for the age of a large set of angiosperm clades. Diversification was modeled as a stochastic, time-homogeneous birth-and-death process that depends on the diversification rate (r) and the relative extinction rate (epsilon). A statistical analysis of the birth and death process was then used to obtain 95% confidence intervals for the expected number of species through time in a clade that diversifies at a rate equal to that of angiosperms as a whole. Confidence intervals were obtained for stem group and for crown group ages in the absence of extinction (e = 0.0) and under a high relative extinction rate (epsilon = 0.9). The standing diversity of angiosperm clades was then compared to expected species diversity according to the background rate of diversification, and, depending on their placement with respect to the calculated confidence intervals, exceedingly species-rich or exceedingly species-poor clades were identified. The rate of diversification for angiosperms as a whole ranges from 0.077 (epsilon = 0.9) to 0.089 (epsilon = 0.0) net speciation events per million years. Ten clades fall above the confidence intervals of expected species diversity, and 13 clades were found to be unexpectedly species poor. The phylogenetic distribution of clades with an exceedingly high number of species suggests that traits that confer high rates of diversification evolved independently in different instances and do not characterize the angiosperms as a whole.

Can Investors Profit from the Prophets? Security Analyst Recommendations and Stock Returns

Abstract: We document that purchasing ~selling short! stocks with the most ~least! favorable consensus recommendations, in conjunction with daily portfolio rebalancing and a timely response to recommendation changes, yield annual abnormal gross returns greater than four percent. Less frequent portfolio rebalancing or a delay in reacting to recommendation changes diminishes these returns; however, they remain significant for the least favorably rated stocks. We also show that high trading levels are required to capture the excess returns generated by the strategies analyzed, entailing substantial transactions costs and leading to abnormal net returns for these strategies that are not reliably greater than zero. THIS STUDY EXAMINES WHETHER INVESTORS can profit from the publicly available recommendations of security analysts. Academic theory and Wall Street practice are clearly at odds regarding this issue. On the one hand, the semistrong form of market efficiency posits that investors should not be able to trade profitably on the basis of publicly available information, such as analyst recommendations. On the other hand, research departments of brokerage houses spend large sums of money on security analysis, presumably because these firms and their clients believe its use can generate superior returns.

Food Insecurity Is Positively Related to Overweight in Women

Abstract: Although individuals with poor food security might be expected to have reduced food intake, and thus reduced body fat and less likelihood of being overweight, these associations have not been adequately studied. The purpose of the current study was to examine the relationship between food insecurity and overweight as measured by body mass index (BMI) using data from the nationally representative 1994-1996 Continuing Survey of Food Intakes by Individuals (CSFII). Overweight was defined as BMI >27.3 kg/m(2) for women and 27.8 kg/m(2) for men. Food insecurity was related to overweight status for women (n = 4509, P < 0.0001), but not for men (n = 4970, P = 0.44). Excluding the 11 severely insecure women, the prevalence of overweight among women increased as food insecurity increased, from 34% for those who were food secure (n = 3447), to 41% for those who were mildly food insecure (n = 966) and to 52% for those who were moderately food insecure (n = 86). Food insecurity remained a significant predictor of overweight status, after adjustment for potentially confounding demographic and lifestyle variables (P < 0.01). In a logistic regression analysis, mildly insecure women were 30% more likely to be overweight than those who were food secure [odds ratio (OR) 1.3, P = 0.005]. Thus, food insecurity had an unexpected and paradoxical association with overweight status among women with a higher prevalence of overweight among the food insecure, and a resulting potential for increased incidence of obesity-related chronic diseases. Given that the rates of both overweight and food insecurity are on the rise, this research area warrants further investigation.

Intention tremor, parkinsonism, and generalized brain atrophy in male carriers of fragile X.

Abstract: The authors report five elderly men with the fragile X premutation who had a progressive action tremor associated with executive function deficits and generalized brain atrophy. These individuals had elevated fragile X mental retardation 1 gene (FMR1) messenger RNA and normal or borderline levels of FMR1 protein. The authors propose that elevations of FMR1 messenger RNA may be causative for a neurodegenerative syndrome in a subgroup of elderly men with the FMR1 premutation.

Using the gravity equation to differentiate among alternative theories of trade

Abstract: The simple gravity equation explains a great deal about the data on bilateral trade flows and is consistent with several theoretical models of trade. We argue that alternative theories nev- ertheless predict subtle differences in key parameter values, depending on whether goods are homogeneous or differentiated and whether or not there are barriers to entry. Our empirical work for differentiated goods delivers results consistent with the theoretical predictions of the monopolistic-competition model, or a reciprocal-dumping model with free entry. Homo- geneous goods are described by a model with national (Armington) product differentiation or