Biomedical subjects

Feng Yuan

Publications and source records attributed to Feng Yuan.

10 recordsLinked to original sources

PubMed2006

Unified picture for single transverse-spin asymmetries in hard-scattering processes.

Using lepton-pair production in hadron-hadron collisions as an example, we explore the relation between two well-known mechanisms for single-transverse-spin asymmetries in hard processes: twist-three quark-gluon correlations when the pair's transverse momentum is large, q perpendicular >> Lambda QCD, and time-reversal-odd and transverse-momentum-dependent parton distributions when q perpendicular is much less than the pair's mass. We find that, although the two mechanisms each have their own domain of validity, they describe the same physics in the kinematic region where they overlap. This unifies the two mechanisms and imposes an important constraint on phenomenological studies.

Journal Article↗

PubMed2006

Intramuscular administration of vascular endothelial growth factor augmenting collateral circulation in a rat hindlimb replantation model.

This study evaluated the effect of exogenous vascular endothelial growth factor (VEGF) on augmentation of collateral circulation in a rat hindlimb replantation model. Twenty-eight rats, divided into four groups, underwent right hindlimb replantation. In experimental Group 1, the rats received daily intramuscular VEGF injections (1 microg/kg). In Group 2, the rats received 25 microg/kg VEGF injections. In Group 3, the rats received 50 microg/kg VEGF injections. In Group 4, the control group, rats received saline injections. Seven days after replantation, the repaired femoral vessels were excised. Seven days after excision of the femoral vessels, toe necrosis ratios of the replanted hindlimbs were grossly examined, and calf blood pressures were measured. Angiography was performed and muscle tissue was biopsied for histology. The results showed that administration of VEGF significantly decreased toe necrosis and improved calf blood pressure ratio, angiographic score, and capillary density in the replanted hindlimbs that underwent late vessel excision. The effect of VEGF was significantly dose-dependent. The authors conclude that VEGF can augment angiogenesis and collateral vessel formation in replanted limbs, and improve survival in replanted limbs with potential late arterial insufficiency.

Analysis of Variance↗

PubMed2005

Microsurgical second dorsal metacarpal artery cutaneous and tenocutaneous flap for distal finger reconstruction: anatomic study and clinical application.

In this paper, we report on the anatomical study of 34 cadaveric forearms with red latex injection and the clinical application of this study to 11 cases of microsurgical second dorsal metacarpal artery (SDMA) flaps. There were 8 cutaneous cases and 3 tenocutaneous cases using SDMA flaps for distal finger reconstruction. The SDMA was classified into 2 types and 4 subtypes according to its anatomical origin and course. Type I (76.5%) originated from the dorsal branch of the radial artery at the snuffbox. Type II (23.5%) originated from the perforating branch of the deep palmar arch at the bases of second and third metacarpal bones. Diameter of the SDMA was 1.2 +/- 0.2 mm at its snuffbox origin, and 1.0 +/- 0.1 mm at the base of the second and third metacarpal bones. Clinically, microsurgical SDMA free flaps were raised and transferred for repair of finger injuries. Ten flaps survived completely. One flap failed due to thrombosis of vascular anastomosis. In conclusion, the second dorsal metacarpal artery is a constant and reliable vessel for microvascular anastomosis in microsurgical SDMA flap transfer. This flap can be used as an alternative for hand and finger reconstruction, and especially repair of a distal phalanx, when either an orthograde or retrograde island SDMA flap is unable to reach the defect.

Adolescent↗

PubMed2005

Microsurgical fibular graft for full-length radius reconstruction after giant-cell tumor resection: a case report.

In this article, we present the treatment of a recurrent giant-cell tumor of the radius with en bloc resection and full-length radius reconstruction with a 24-cm long microsurgical fibular graft. At time of 8-year follow-up, there was no evidence of tumor recurrence. A satisfactory range of motion of the elbow, wrist, and forearm was maintained. There was no instability in the joints, and grip strength measured 63% of the opposite side. With appropriate dynamic tendon transfer, this procedure can provide an alternative method for reconstruction of the full-length radius after tumor resection, with functional and durable results.

Adult↗

PubMed2005

[Effect of femoral vein-occlusion on replanted limb survival at different stages].

OBJECTIVE: To study the effect of vein-occlusion on the replanted limb survival in SD rats at different stages. METHODS: Twenty-five adult SD rats were randomly divided into 5 groups according to the time of the femoral vein occlusion after the replanted limbs: 2-, 3-, 4-, 6-, and 8-day groups. The limbs were observed through naked eye, measurement of dermal temperature and angiography. RESULTS: No formation of collateral veinlet was found, and necrosis was seen in the replanted limbs of 2-, 3-day groups. Reflux-vein was gradually increased in the replanted limbs of 4, 6, and 8 day groups. Angiographic score of capillary density and dermal temperature in the thigh muscles were greater in groups 4-, 6-, and 8-day than in groups 2- and 3-day. CONCLUSION: Within 2 and 3 days,the replanted limbs of SD rats will necrose because of vein-occlusion; and 4 days later the replanted limbs can survive depending on the reflux-vein of new collateral veinlet.

Animals↗

PubMed2005

[Clinical application of second dorsal metacarpal artery flap in hand surgery].

OBJECTIVE: To summarize the clinical experiences of various types of the second dorsal metacarpal artery (SDMA) flap for hand reconstruction. METHODS: From 1988 to 2003, 139 SDMA flaps were transferred for hand injuries. The flaps were used in 5 types according to vascularization and technique in transplantation:orthograde pedicled island SDMA flaps in 37 cases (cutaneous in 24 and teno-cutaneous in 13), retrograde pedicled island SDMA flaps in 25 cases (cutaneous in 19 and teno-cutaneous in 6), double pivot SDMA flaps in 36 cases (cutaneous in 28 and tenocutaneous in 8), distal perforator branch pedicled flaps in 19 cases (cutaneous in 16 and composite in 3), free SDMA flaps in 22 cases (cutaneous in 15 and composite in 7). The skin islands were 3.0 cm x 1.5 cm to 6.3 cm x 5.0 cm in size. RESULTS: Of the 139 flaps, 135 flaps survived completely, 3 survived partially, and 1 failed in the operation because of intractable vascular spasm. Follow-up was done in 116 cases for 12 to 57 months. The flap had good texture and color match. The two-point discrimination was 5 to 9 mm in 78 sensate flaps, while it was 10 to 15 mm in 38 nonsensate flaps. In 21 tenocutaneous flaps, the TAM score of range of motion was 60% to 70% of the healthy side. CONCLUSION: The SDMA flap has a constant and reliable vessel and a thin, pliable, and good-quality skin. It is versatile in creating composite flaps. It is a good flap resource for hand and finger reconstruction.

Adolescent↗

PubMed2005

[Applied anatomy of the second dorsal metacarpal artery island flap with double pivot points].

OBJECTIVE: To provide the anatomic bases for clinical application of the second dorsal metacarpal artery (SDMA) island flap with double pivot points. METHODS: The origin, branches and distribution of the recurrent cutaneous branch of the SDMA were observed in 30 adult fresh cadaver specimens, which were illustrated with special dye. Eighteen cases of skin defects of the thumb were repaired with the SDMA island flap. The defect locations were the dorsal part in 11 cases and palmar part in 7 cases, including 3 cases of defect in association with long pollical extensor defect and 2 cases of defect in association with dorsal skin defect of proximal finger. The flap area ranged from 2 cm x 3 cm to 3 cm x 5 cm. RESULTS: The appearance of the recurrent cutaneous branch of the SDMA was observed in all cases (100%), which originated 0.5 +/- 0.2 cm distant from the distal intersections between the SDMA and the index extensor and disappeared 1.2 +/- 0.5 cm distant from the proximal metacarpophalangeal joint. The branches of 1.7 +/- 0.7 were seen with a longitudinal fan-like distribution forward proximal part on the deep surface of the dorsal superficial vein. The exradius and the length of the recurrent cutaneous branch of the SDMA were 0.3 +/- 0.1 mm and 6.5 +/- 0.8 mm, respectively. The transplanted flaps survived in all cases and 16 cases were followed up for 8-14 months. The colour and appearance of the skin were satisfactory. The two-point discriminations were 0.9 mm in 3 cases by bridging digital nerve and 1.1 mm in 9 cases by anastomosing dorsal digital nerve; while the two-point discrimination was 13-15 mm in 4 cases without anastomosing nerve. CONCLUSION: The origin, branches and distribution of the recurrent cutaneous branch of the SDMA is constant, which provide a potentially longer pedicle and increase the possibility to rotate the flap and also avoid the donor skin defect of rotation of the flap.

Adult↗

PubMed2004

Probing quark-distribution amplitudes through generalized parton distributions at large momentum transfer.

In the large momentum transfer limit, generalized parton distributions can be calculated through a QCD factorization theorem which involves perturbatively calculable hard kernels and light-cone parton distribution amplitudes of hadrons. We illustrate this through the H(q)(x,xi,t) distribution for the pion and the proton, presenting the hard kernels at leading order. As a result, experimental data on the generalized parton distributions in this regime can be used to determine the functional form of the parton distribution amplitudes which has thus far been quite challenging to obtain. Our result can also be used as a constraint in phenomenological generalized parton distribution parametrizations.

Journal Article↗

PubMed2003

Perturbative QCD analysis of the nucleon's Pauli form factor F2(Q2).

We perform a perturbative QCD analysis of the nucleon's Pauli form factor F2(Q2) in the asymptotically large Q2 limit. We find that the leading contribution to F2(Q2) has a 1/Q6 power behavior, consistent with the well-known result in the literature. Its coefficient depends on the leading- and subleading-twist light-cone wave functions of the nucleon, the latter describing the quarks with one unit of orbital angular momentum. We also derive at the logarithmic accuracy the asymptotic scaling F2(Q2)/F(1)(Q2) approximately (log2Q2/Lambda2)/Q2 which describes recent Jefferson Lab data well.

Journal Article↗

PubMed2003

Generalized counting rule for hard exclusive processes.

We derive a generalized counting rule for hard exclusive processes involving parton orbital angular momentum and hadron helicity flip. We start with a systematic way to enumerate the Fock components of a hadronic light-cone wave function with n partons and orbital angular momentum projection l(z). We show that the wave-function amplitude psi(n)(x(i),k(i perpendicular ),l(zi)) has a leading behavior 1/(k(2)( perpendicular ))[n(+|l(z)|+min(n(')+|l(')(z)|)]/2-1) when all parton transverse momenta are uniformly large, where n(') and l(')(z) are the number of partons and orbital angular momentum projection, respectively, of an amplitude that mixes under renormalization. Besides the generalized counting rule, the result can be used as a constraint in modeling the hadronic light-cone wave functions.

Journal Article↗