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1.
Nature ; 599(7886): 565-570, 2021 11.
Article in English | MEDLINE | ID: mdl-34819691

ABSTRACT

Neutrinos exist in one of three types or 'flavours'-electron, muon and tau neutrinos-and oscillate from one flavour to another when propagating through space. This phenomena is one of the few that cannot be described using the standard model of particle physics (reviewed in ref. 1), and so its experimental study can provide new insight into the nature of our Universe (reviewed in ref. 2). Neutrinos oscillate as a function of their propagation distance (L) divided by their energy (E). Therefore, experiments extract oscillation parameters by measuring their energy distribution at different locations. As accelerator-based oscillation experiments cannot directly measure E, the interpretation of these experiments relies heavily on phenomenological models of neutrino-nucleus interactions to infer E. Here we exploit the similarity of electron-nucleus and neutrino-nucleus interactions, and use electron scattering data with known beam energies to test energy reconstruction methods and interaction models. We find that even in simple interactions where no pions are detected, only a small fraction of events reconstruct to the correct incident energy. More importantly, widely used interaction models reproduce the reconstructed energy distribution only qualitatively and the quality of the reproduction varies strongly with beam energy. This shows both the need and the pathway to improve current models to meet the requirements of next-generation, high-precision experiments such as Hyper-Kamiokande (Japan)3 and DUNE (USA)4.

2.
Phys Rev Lett ; 124(9): 092002, 2020 Mar 06.
Article in English | MEDLINE | ID: mdl-32202871

ABSTRACT

Mechanisms of spin-flavor SU(6) symmetry breaking in quantum chromodynamics (QCD) are studied via an extraction of the free neutron structure function from a global analysis of deep inelastic scattering (DIS) data on the proton and on nuclei from A=2 (deuterium) to 208 (lead). Modification of the structure function of nucleons bound in atomic nuclei (known as the EMC effect) are consistently accounted for within the framework of a universal modification of nucleons in short-range correlated (SRC) pairs. Our extracted neutron-to-proton structure function ratio F_{2}^{n}/F_{2}^{p} becomes constant for x_{B}≥0.6, equaling 0.47±0.04 as x_{B}→1, in agreement with theoretical predictions of perturbative QCD and the Dyson-Schwinger equation, and in disagreement with predictions of the scalar diquark dominance model. We also predict F_{2}^{^{3}He}/F_{2}^{^{3}H}, recently measured, as yet unpublished, by the MARATHON Collaboration, the nuclear correction function that is needed to extract F_{2}^{n}/F_{2}^{p} from F_{2}^{^{3}He}/F_{2}^{^{3}H}, and the theoretical uncertainty associated with this extraction.

3.
Nature ; 578(7796): 540-544, 2020 02.
Article in English | MEDLINE | ID: mdl-32103193

ABSTRACT

The strong nuclear interaction between nucleons (protons and neutrons) is the effective force that holds the atomic nucleus together. This force stems from fundamental interactions between quarks and gluons (the constituents of nucleons) that are described by the equations of quantum chromodynamics. However, as these equations cannot be solved directly, nuclear interactions are described using simplified models, which are well constrained at typical inter-nucleon distances1-5 but not at shorter distances. This limits our ability to describe high-density nuclear matter such as that in the cores of neutron stars6. Here we use high-energy electron scattering measurements that isolate nucleon pairs in short-distance, high-momentum configurations7-9, accessing a kinematical regime that has not been previously explored by experiments, corresponding to relative momenta between the pair above 400 megaelectronvolts per c (c, speed of light in vacuum). As the relative momentum between two nucleons increases and their separation thereby decreases, we observe a transition from a spin-dependent tensor force to a predominantly spin-independent scalar force. These results demonstrate the usefulness of using such measurements to study the nuclear interaction at short distances and also support the use of point-like nucleon models with two- and three-body effective interactions to describe nuclear systems up to densities several times higher than the central density of the nucleus.

4.
Phys Rev Lett ; 122(17): 172502, 2019 May 03.
Article in English | MEDLINE | ID: mdl-31107086

ABSTRACT

We measured the triple coincidence A(e,e^{'}np) and A(e,e^{'}pp) reactions on carbon, aluminum, iron, and lead targets at Q^{2}>1.5 (GeV/c)^{2}, x_{B}>1.1 and missing momentum >400 MeV/c. This was the first direct measurement of both proton-proton (pp) and neutron-proton (np) short-range correlated (SRC) pair knockout from heavy asymmetric nuclei. For all measured nuclei, the average proton-proton (pp) to neutron-proton (np) reduced cross-section ratio is about 6%, in agreement with previous indirect measurements. Correcting for single-charge exchange effects decreased the SRC pairs ratio to ∼3%, which is lower than previous results. Comparisons to theoretical generalized contact formalism (GCF) cross-section calculations show good agreement using both phenomenological and chiral nucleon-nucleon potentials, favoring a lower pp to np pair ratio. The ability of the GCF calculation to describe the experimental data using either phenomenological or chiral potentials suggests possible reduction of scale and scheme dependence in cross-section ratios. Our results also support the high-resolution description of high-momentum states being predominantly due to nucleons in SRC pairs.

5.
Phys Rev Lett ; 121(9): 092501, 2018 Aug 31.
Article in English | MEDLINE | ID: mdl-30230869

ABSTRACT

Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum (k_{F}). A fundamental characteristic of SRC pairs is having large relative momenta as compared to k_{F}, and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton (pp) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the A(e,e^{'}pp) reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to 170 MeV/c, approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.

6.
Phys Rev Lett ; 114(6): 062003, 2015 Feb 13.
Article in English | MEDLINE | ID: mdl-25723209

ABSTRACT

There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p) from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ϵ) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ϵ at Q(2)=1.45 GeV(2). This measurement is consistent with the size of the form factor discrepancy at Q(2)≈1.75 GeV(2) and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV(2).

7.
Science ; 346(6209): 614-7, 2014 Oct 31.
Article in English | MEDLINE | ID: mdl-25323697

ABSTRACT

The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using (12)C, (27)Al, (56)Fe, and (208)Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.

8.
Horm Metab Res ; 46(12): 841-4, 2014 Nov.
Article in English | MEDLINE | ID: mdl-25232907

ABSTRACT

GNAS is a complex imprinted locus with multiple oppositely imprinted gene products, including the G protein α-subunit Gsα that is expressed primarily from the maternal allele in some tissues and the Gsα isoform XLαs that is expressed only from the paternal allele. Maternal Gsα mutations in mice and in patients with Albright hereditary osteodystrophy lead to obesity, insulin resistance, and hyperlipidemia. Studies in mice show that these effects are primarily due to Gsα imprinting in the central nervous system and that Gsα deficiency in one or more regions of the central nervous system lead to reduced sympathetic nervous system and energy expenditure without affecting food intake. Loss of Gsα in the central nervous system appears to lead to these effects primarily through impairment of melanocortin signaling. Loss of XLαs in mice leads to opposite effects on energy and glucose metabolism.


Subject(s)
Energy Metabolism , GTP-Binding Protein alpha Subunits, Gs/metabolism , Glucose/metabolism , Animals , Central Nervous System/metabolism , GTP-Binding Protein alpha Subunits, Gs/genetics , Humans , Mutation/genetics , Phenotype
9.
ACS Appl Mater Interfaces ; 4(3): 1194-9, 2012 Mar.
Article in English | MEDLINE | ID: mdl-22329838

ABSTRACT

Capacitive deionization (CDI) is a water desalination technology in which salt ions are removed from brackish water by flowing through a spacer channel with porous electrodes on each side. Upon applying a voltage difference between the two electrodes, cations move to and are accumulated in electrostatic double layers inside the negatively charged cathode and the anions are removed by the positively charged anode. One of the key parameters for commercial realization of CDI is the salt adsorption capacity of the electrodes. State-of-the-art electrode materials are based on porous activated carbon particles or carbon aerogels. Here we report the use for CDI of carbide-derived carbon (CDC), a porous material with well-defined and tunable pore sizes in the sub-nanometer range. When comparing electrodes made with CDC with electrodes based on activated carbon, we find a significantly higher salt adsorption capacity in the relevant cell voltage window of 1.2-1.4 V. The measured adsorption capacity for four materials tested negatively correlates with known metrics for pore structure of the carbon powders such as total pore volume and BET-area, but is positively correlated with the volume of pores of sizes <1 nm, suggesting the relevance of these sub-nanometer pores for ion adsorption. The charge efficiency, being the ratio of equilibrium salt adsorption over charge, does not depend much on the type of material, indicating that materials that have been identified for high charge storage capacity can also be highly suitable for CDI. This work shows the potential of materials with well-defined sub-nanometer pore sizes for energy-efficient water desalination.


Subject(s)
Carbon/chemistry , Salinity , Sodium Chloride/isolation & purification , Water Purification/methods , Water/chemistry , Adsorption , Electricity , Electrodes , Ions , Models, Chemical , Porosity
10.
Surg Endosc ; 26(3): 823-30, 2012 Mar.
Article in English | MEDLINE | ID: mdl-22083321

ABSTRACT

BACKGROUND: Glucose-6-phosphate dehydrogenase (G6PD) is the rate-limiting enzyme of the pentose phosphate pathway that provides the majority of NADPH required for lipid biosynthesis. G6PD overexpression has been implicated in insulin resistance, hyperlipidemia, and increased oxidative stress in animals. This study examines G6PD expression in obese diabetic and nondiabetic subjects pre- and post-laparoscopic Roux-en-Y gastric bypass (LRYGB). METHODS: Patients undergoing LRYGB were recruited for the IRB-approved study and placed in either the diabetic (n = 11) or nondiabetic group (n = 16) (diabetic, HbA1c > 6.5%; nondiabetic, HbA1c < 6.0%). Blood samples were collected at baseline and throughout the first 3 postoperative months. Liver, adipose, and omental samples were taken during surgery. Results are expressed as mean ± SEM and were compared statistically using the Mann-Whitney test. RESULTS: The two groups were not significantly different at baseline except for fasting glucose and HbA1c. G6PD activity (nm/min/mg protein) was significantly higher in red blood cells (RBCs) (3.12 ± 1.39 vs. 0.67 ± 0.14) and liver (17.23 ± 2.40 vs. 9.74 ± 2.18) in diabetics compared to nondiabetics. There was good correlation between increased liver G6PD activity and the severity of diabetes as measured by HbA1c (r (2) = 0.525) and fasting glucose (r (2) = 0.542). No significant difference was found in the adipose or omental G6PD expression. Both groups experienced a significant increase in G6PD blood activity shortly following surgery (1 week) followed by a reduction 3 months after surgery. CONCLUSION: These results are the first ever seen in human subjects and demonstrate increased G6PD activity in diabetics compared to nondiabetics. These results suggest a correlation between G6PD activity and the severity of type 2 diabetes. The early increases in G6PD activity after LRYGB were unexpected and longer follow-up is needed to determine the effects of LRYGB on G6PD activity.


Subject(s)
Diabetes Mellitus, Type 2/enzymology , Gastric Bypass/methods , Glucosephosphate Dehydrogenase/metabolism , Laparoscopy/methods , Obesity, Morbid/surgery , Adipose Tissue/enzymology , Adult , Erythrocytes/enzymology , Female , Glycated Hemoglobin/metabolism , Humans , Liver/enzymology , Male , Middle Aged , Obesity, Morbid/enzymology , Omentum/enzymology
11.
Phys Rev Lett ; 106(5): 052301, 2011 Feb 04.
Article in English | MEDLINE | ID: mdl-21405385

ABSTRACT

This Letter shows quantitatively that the magnitude of the EMC effect measured in electron deep inelastic scattering at intermediate x(B), 0.35≤x(B)≤0.7, is linearly related to the short range correlation (SRC) scale factor obtained from electron inclusive scattering at x(B)≥1. The observed phenomenological relationship is used to extract the ratio of the deuteron to the free pn pair cross sections and F(2)(n)/F(2)(p), the ratio of the free neutron to free proton structure functions. We speculate that the observed correlation is because both the EMC effect and SRC are dominated by the high virtuality (high momentum) nucleons in the nucleus.

12.
Phys Rev Lett ; 105(22): 222501, 2010 Nov 26.
Article in English | MEDLINE | ID: mdl-21231381

ABSTRACT

We have measured the 3He(e,e' pp)n reaction at an incident energy of 4.7 GeV over a wide kinematic range. We identified spectator correlated pp and pn nucleon pairs by using kinematic cuts and measured their relative and total momentum distributions. This is the first measurement of the ratio of pp to pn pairs as a function of pair total momentum p(tot). For pair relative momenta between 0.3 and 0.5 GeV/c, the ratio is very small at low p(tot) and rises to approximately 0.5 at large p(tot). This shows the dominance of tensor over central correlations at this relative momentum.

13.
Int J Obes (Lond) ; 34(1): 6-17, 2010 Jan.
Article in English | MEDLINE | ID: mdl-19844212

ABSTRACT

Genomic imprinting is an epigenetic phenomenon affecting a small number of genes, which leads to differential expression from the two parental alleles. Imprinted genes are known to regulate fetal growth and a 'kinship' or 'parental conflict' model predicts that paternally and maternally expressed imprinted genes promote and inhibit fetal growth, respectively. In this review we examine the role of imprinted genes in postnatal growth and metabolism, with an emphasis on the GNAS/Gnas locus. GNAS is a complex imprinted locus with multiple oppositely imprinted gene products, including the G-protein alpha-subunit G(s)alpha that is expressed primarily from the maternal allele in some tissues and the G(s)alpha isoform XLalphas that is expressed only from the paternal allele. Maternal, but not paternal, G(s)alpha mutations lead to obesity in Albright hereditary osteodystrophy. Mouse studies show that this phenomenon is due to G(s)alpha imprinting in the central nervous system leading to a specific defect in the ability of central melanocortins to stimulate sympathetic nervous system activity and energy expenditure. In contrast mutation of paternally expressed XLalphas leads to opposite metabolic effects in mice. Although these findings conform to the 'kinship' model, the effects of other imprinted genes on body weight regulation do not conform to this model.


Subject(s)
GTP-Binding Protein alpha Subunits, Gs/genetics , Genomic Imprinting/genetics , Obesity/genetics , Angelman Syndrome/genetics , Animals , Body Weight/genetics , Chromogranins , Energy Metabolism/genetics , Gene Expression , Gene Silencing , Growth/genetics , Mice , Mice, Knockout , Mutation/physiology , Prader-Willi Syndrome/genetics
14.
Phys Rev Lett ; 96(8): 082501, 2006 Mar 03.
Article in English | MEDLINE | ID: mdl-16606174

ABSTRACT

The ratios of inclusive electron scattering cross sections of 4He, 12C, and 56Fe to 3He have been measured at 1 < xB <. At Q2 > 1.4 GeV2, the ratios exhibit two separate plateaus, at 1.5 < xB < 2 and at xB > 2.25. This pattern is predicted by models that include 2- and 3-nucleon short-range correlations (SRC). Relative to A = 3, the per-nucleon probabilities of 3-nucleon SRC are 2.3, 3.1, and 4.4 times larger for A = 4, 12, and 56. This is the first measurement of 3-nucleon SRC probabilities in nuclei.

15.
Obes Surg ; 14(8): 1031-5, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15479590

ABSTRACT

BACKGROUND: This study examines the effect of weight loss following laparoscopic Roux-en-Y gastric bypass (RYGBP) for morbid obesity on prescription drug costs in patients over the age of 54. METHODS: 78 patients aged 55 to 75 who met the inclusion criteria were identified in a database of 1,060 morbidly obese patients undergoing LRYGBP between March 2001 and March 2003. All prescription drugs and dosages were recorded preoperatively and postoperatively at 6 months, 1 year, and yearly thereafter. Drug history was obtained from the patient and verified by records from referring physicians' offices. The cost of a 30-day supply of each drug was obtained from 3 retail sources and averaged. RESULTS: The average pre-LRYGBP cost of prescription drugs was $368.65 per month per patient. The average annualized cost at 6 months after LRYGBP was $119.10 per month (down 68%), at 1 year $118.67 (down 68%) and at 2 years $104.68 per month (down 72%). CONCLUSIONS: Weight loss resulting from LRYGBP significantly reduces obesity-related morbidities, resulting in a substantial reduction in medication needs in patients over the age of 54. The projected cost savings realized in the 78 patients in this study amounts to approximately $240,566.04 annually.


Subject(s)
Gastric Bypass/economics , Obesity, Morbid/economics , Prescription Fees , Age Factors , Aged , Anastomosis, Roux-en-Y , Comorbidity , Cost-Benefit Analysis , Female , Gastric Bypass/methods , Humans , Male , Middle Aged , Obesity, Morbid/epidemiology , Obesity, Morbid/surgery , Time Factors , Treatment Outcome , Weight Loss
16.
Phys Rev Lett ; 92(5): 052303, 2004 Feb 06.
Article in English | MEDLINE | ID: mdl-14995301

ABSTRACT

We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic range. The kinetic energy distribution for "fast" nucleons (p>250 MeV/c) peaks where two nucleons each have 20% or less, and the third nucleon has most of the transferred energy. These fast pp and pn pairs are back to back with little momentum along the three-momentum transfer, indicating that they are spectators. Calculations by Sargsian and by Laget also indicate that we have measured distorted two-nucleon momentum distributions by striking one nucleon and detecting the spectator correlated pair.

18.
Cancer ; 92(7): 1943-8, 2001 Oct 01.
Article in English | MEDLINE | ID: mdl-11745269

ABSTRACT

BACKGROUND: Vertebrates have special structures at the ends of their chromosomes, known as telomeres, which may provide the chromosomes with stability and protect them from exonucleolytic degradation. The shortening of telomeric DNA with each cell division may lead to cell cycle arrest and/or apoptosis of a normal human somatic cell. Telomerase, an RNA-dependent DNA polymerase, elongates the 3'-ends of telomeric DNA. Thus, the presence of telomerase activity may reflect a cell's potential immortal state. The telomerase complex is comprised of several subunits. In the current study, the authors describe the use of laser capture microdissection (LCM) to procure pure matched tumor and normal cell populations from histologic sections and to determine the expression of telomerase subunits in these purified samples. METHODS: Pure matched tumor and normal prostate epithelial cells were procured by LCM using fresh frozen tissue samples obtained from patients undergoing radical prostatectomy. RNA was extracted from LCM captured cells, and the subunits for telomerase were assayed by reverse transcriptase-polymerase chain reaction. RESULTS: In 18 samples that were captured with LCM, only the catalytic subunit of telomerase, or hTERT, was found to be discriminatory between tumor cells (17 of 18 specimens, 94.4%) and nontumor cells (none of 18 specimens). TP1, a protein that has been shown to be associated with telomerase activity, was expressed in 3 of 18 normal cells (16.7%) and 15 of 18 tumor cells (83.3%). The RNA subunit of telomerase, or hTR, was expressed in 10 of 18 normal cells (55.6%) and 18 of 18 tumor cells (100%). There was no apparent correlation between telomerase subunit(s) expression and Gleason sum score. CONCLUSIONS: Molecular analyses of LCM cells from prostate carcinoma patient samples demonstrated transcriptional up-regulation of all telomerase subunits in the prostatic epithelium. However, only the catalytic subunit of telomerase, hTERT, was found to be discriminatory between neoplastic versus normal cells (94.4% vs. 0%). This finding suggests that the hTERT subunit may be a useful marker for the detection of prostate carcinoma and/or a potential target for therapy.


Subject(s)
Prostate/enzymology , Prostatic Neoplasms/enzymology , Telomerase/metabolism , Catalytic Domain , DNA-Binding Proteins , Epithelial Cells/enzymology , Humans , Male , Prostate/pathology , Prostatic Neoplasms/pathology , RNA/isolation & purification , Reverse Transcriptase Polymerase Chain Reaction
19.
Surgery ; 130(6): 991-8, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11742328

ABSTRACT

BACKGROUND: Patients with multiple endocrine neoplasia type 1 and hyperparathyroidism often undergo multiple operations because of inadequate initial surgery, presence of supernumerary and ectopic glands, regrowth of remnant glands, or autograft hyperfunction. Management of this patient population is complex. METHODS: From January 1975 to December 2000 we performed 94 reoperative parathyroidectomies consisting of 79 neck reexplorations, 12 autograft removals, and 3 median sternotomies in 75 patients. Data were gathered by retrospective chart review and follow-up telephone interviews. RESULTS: Excluding autograft excision, reoperative surgery was successful (normocalcemia longer than 6 months) in 91%; autograft removal was successful in only 58%. With a median follow-up of 59 months, 64% of patients are currently free from hypercalcemia, and this outcome was not influenced by the total number of glands resected. The median time to recurrent hypercalcemia was 125 months. Thirty patients received an autograft after reoperation. The complication rate for all reoperations was 12%, including permanent recurrent laryngeal nerve injury in 2 patients (2.1%). CONCLUSIONS: Reoperative parathyroidectomy in patients with multiple endocrine neoplasia type 1 was safe and successful in the majority of patients; however, recurrent hyperparathyroidism is likely to develop in most individuals beyond 10 years of follow-up. The total number of glands accounted for after reoperation is not associated with successful outcome.


Subject(s)
Hyperparathyroidism/surgery , Multiple Endocrine Neoplasia Type 1/surgery , Adult , Aged , Female , Humans , Male , Middle Aged , Monitoring, Intraoperative , Parathyroid Glands/transplantation , Parathyroid Hormone/blood , Parathyroidectomy , Postoperative Complications , Reoperation , Transplantation, Autologous
20.
Biol Psychiatry ; 50(12): 927-31, 2001 Dec 15.
Article in English | MEDLINE | ID: mdl-11750888

ABSTRACT

Genomic imprinting is an epigenetic phenomenon affecting a small number of genes that leads to expression from only one parental allele. Several imprinted genes are important for neurologic development and function and several neurobehavioral disorders are caused by genetic defects involving imprinted genes. For some genes, the imprinting is tissue specific, leading to biallelic expression in some tissues and monoallelic expression in other tissues. Defects involving these genes may produce one restricted phenotype due to loss of expression of the gene product in tissues where the gene is imprinted and, in some instances, a second phenotype due to haploinsufficiency of the gene product in tissues where it is biallelically expressed.


Subject(s)
Gene Expression Regulation , Genetic Heterogeneity , Genomic Imprinting/genetics , Alleles , Angelman Syndrome/genetics , DNA Methylation , Genomic Imprinting/physiology , Haploidy , Humans , Phenotype , Prader-Willi Syndrome/genetics , Pseudohypoparathyroidism/genetics , Uniparental Disomy/genetics
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