Ring Reconstruction Research Articles

Reconstruction of the pelvic ring in iliac or iliosacral resections: allograft or autograft?

The necessity to reconstruct the pelvic ring after an iliac or iliosacral resection is still debated. Different reconstructive techniques are available, including autologous and homologous graft and custom-made prosthesis. The aim of this study was to evaluate the functional outcome and complications of patients who underwent resection of iliac bone and part of the sacrum for primary bone tumour and reconstruction with an allograft or autograft. We retrospectively evaluated 18 patients (10 males and 8 female) with a mean age of 28years (range 9-56) who were operated between 1992 and 2015. Six patients were reconstructed with an autograft (Group A) and 12 patients with an allograft (Group B). All complications were recorded. At final follow-up, patients with the original reconstruction still in site were functionally evaluated with MSTS Score. Mean follow-up time was 107months (range 4-221). Two patients (11.1%) had an external hemipelvectomy for local recurrence, and 3 patients died of the disease. Mean MSTS Score was comparable between the two groups 21.7 (range 20-25) in Group A and 19.9 (range 4-28) in Group B. Patients with partial sacral resection had an increased risk of local recurrence and lower MSTS Score [15.5 (range 7-20) vs. 22.2 (range 4-28)]. Biological reconstruction of pelvic ring with autologous or homologous bone graft gives acceptable functional results. However, the decision on how to reconstruct the pelvic ring after iliac resection should be taken on a patient-by-patient basis.

New ideas for ring formation and reconstruction in water-Cherenkov detectors

Water-Cherenkov detector technology is well established as is easily seen in the almost identical designs of Kamiokande, Super- and Hyper-Kamiokande. We explore methods to further improve upon their success by extracting directional information from originally lost photons using reflectors placed in the inactive space between PMTs. The reflected photons form a secondary antipodal ring, sensitive to the vertex position and track topology. We further show how ring reconstruction algorithms can benefit from modeling variations of the Cherenkov profile due to showering. Monte Carlo based quantitative estimates are accompanied by discussions of strategies to overcome potential issues with the presented methods. A new CNN-architecture to efficiently implement the cylindrical topology and geometry is also presented.

L0TP+: the Upgrade of the NA62 Level-0 Trigger Processor

The L0TP+ initiative is aimed at the upgrade of the FPGA-based Level-0 Trigger Processor (L0TP) of the NA62 experiment at CERN for the post-LS2 data taking, which is expected to happen at 100% of design beam intensity, corresponding to about 3.3 × 1012 protons per pulse on the beryllium target used to produce the kaons beam. Although tests performed at the end of 2018 showed a substantial robustness of the L0TP system also at full beam intensity, there are several reasons to motivate such an upgrade: i) avoid FPGA platform obsolescence, ii) make room for improvements in the firmware design leveraging a more capable FPGA device, iii) add new functionalities, iv) support the 4 beam intensity increase foreseen in future experiment upgrades. We singled out the Xilinx Virtex UltraScale+ VCU118 development board as the ideal platform for the project. L0TP+ seamless integration into the current NA62 TDAQ system and exact matching of L0TP functionalities represent the main requirements and focus of the project; nevertheless, the final design will include additional features, such as a PCIe RDMA engine to enable processing on CPU and GPU accelerators, and the partial reconfiguration of trigger firmware starting from a high level language description (C/C++). The latter capability is enabled by modern High Level Synthesis (HLS) tools, but to what extent this methodology can be applied to perform complex tasks in the L0 trigger, with its stringent latency requirements and the limits imposed by single FPGA resources, is currently being investigated. As a test case for this scenario we considered the online reconstruction of the RICH detector rings on an HLS generated module, using a dedicated primitives data stream with PM hits IDs. Besides, the chosen platform supports the Virtex Ultrascale+ FPGA wide I/O capabilities, allowing for straightforward integration of primitive streams from additional sub-detectors in order to improve the performance of the trigger.

Methodological aspect of landscape and ecological reconstruction of Green ring around Volgograd (Stalingrad)

The research is intended for the model development of the external Green ring of the town forming the barrier from the negative natural and climatic phenomena with the purpose to ensure a comfortable sphere of the internal living space. The paper present new landscape decisions increasing the potential of the berry and fruit species assortment of the new species-varietal zoning. The authors analyze the history of forming the Green ring of Volgograd (Stalingrad) from the perspective of the urbanized forestry science. The main methods used in the research are: the method of system analysis; modeling and experimental design. The methodology is based on the modeling and designing plantings of the various functional purposes, taking into consideration the current trends in the urban science landscape design. The developed methodology of a new construction and reconstruction of the green ring can be used in the domestic and in the foreign design in the similar environmental conditions. The analysis of the experience of a green ring forming allowed one to re-evaluate the landscape and the ecological solutions in organizing a comfortable town environment. The experimental design was supported by the developed model of the Green ring of the town.

En Bloc Resection and Pelvic Ring Reconstruction for Primary Malignant Bone Tumors Involving Sacroiliac Joint.

ObjectiveTo observe the process of sacroiliac joint invasion by primary malignant tumors of sacrum and iliac bone, and to explore the methods of surgical resection and reconstruction.MethodsFrom January 2009 to November 2017, there were nine patients with primary malignant bone tumors involving sacroiliac joints, five males and four females, aged from 16 to 63 years, with an average age of 35 years. Of these there were three cases of primitive neuroectodermal tumors, three cases of chondrosarcoma, and three cases of osteosarcoma. Pelvic ring reconstruction was performed with longitudinal half sacrum, sacroiliac joint and partial iliac bone block excision and screw‐rod system combined with bone grafting.ResultsThe operation time was 155–310 min, with an average of 245 ± 55 min, and the bleeding volume was 1400–8500 ml, with an average of 3111 ± 2189 ml. Follow‐up ranged from 5 to 108 months, with a median follow‐up of 24 months. Three patients (33.3%) had local recurrence, three patients (33.3%) survived without tumors, and one patient had lung metastasis 2 years after operation, and survived with tumors. Five patients (55.6%) died, of which four died of lung metastasis and one died of brain metastasis. Survival analysis showed that the 3‐year overall survival rate was 57%. Bone grafts did not heal in four patients, and bone grafts healed in five patients. The healing time ranged from 5 to 7 months, with an average of 6.2 months. Complications: one patient developed deep infection 2 months after operation; one patient had skin edge necrosis; titanium rod loosening and displacement were found in two patients with nonunion of bone graft, and no fracture of nail rod was found. The MSTS 93 functional score of nine patients ranged from 20% to 50%, with an average of 34%.ConclusionThe tumors around the sacroiliac joint often invade the contralateral bone by ligament, and the en bloc resection and pelvic ring reconstruction for primary malignant bone tumors involving sacroiliac joint was feasible.

Automatic tandem and ring reconstruction using MRI for cervical cancer brachytherapy.

The MRI-guided cervical cancer brachytherapy provides unparalleled soft-tissue contrast for target and normal tissue contouring, but eliminates the ability to use conventional metallic fiducials for radiation source path reconstruction as required for treatment planning. Instead, the source path is reconstructed by manually aligning a library model to the signal void produced by the applicator, which takes time intraoperatively and precludes fully automated treatment planning. The purpose of this study is to present and validate an algorithm to automatically reconstruct tandem and ring applicators using MRI for cervical cancer brachytherapy treatment planning. Applicators were reconstructed using T2-weighted MR images acquired at 1.5T from 33 brachytherapy fractions including 10 patients using a model-to-image registration algorithm. The algorithm involves (a) image filtering and maximum intensity projection to highlight the applicator, (b) ring center identification using the circular Hough transform, and (c) three-dimensional surface model registration, optimized by maximizing the image intensity gradient normal to the model surface. Two independent observers manually reconstructed all applicators, enabling the calculation of interobserver variability and establishing a ground truth. Algorithm variability was calculated by comparing algorithm results to each individual observer, and algorithm accuracy was calculated by comparing algorithm results to the ground truth. The algorithm variability and accuracy were compared to the interobserver variability using paired t-tests. Mean±SD interobserver variability was 0.83±0.31mm and 0.78±0.29mm for the ring and tandem, respectively. The algorithm had mean±SD variability and accuracy of 0.72±0.32mm (P=0.02) and 0.60±0.24mm (P=0.0005) for the ring, and 0.70±0.29mm (P=0.11) and 0.58±0.24mm (P=0.004) for the tandem, respectively. The algorithm variability and accuracy were within the interobserver variability measured in this study. The algorithm accuracy and mean execution time of 10.0s are sufficient for clinical tandem and ring reconstruction, and are a step toward fully automated tandem and ring brachytherapy treatment planning.

Tree Ring Reconstructions of Stemwood Biomass Indicate Increases in the Growth Rate of Black Spruce Trees Across Boreal Forests of Canada

AbstractThe claim that changes in atmospheric composition and climate have enhanced the growth rate of trees is prevalent in science, yet it is not supported by many recent tree ring studies. In this study, we analyzed historical time trends in stemwood biomass growth derived from black spruce (Picea mariana (Mill.) BSP) trees at 248 plots across Canada. The sample consisted of trees that were live and dominant at the time of sampling (LDS). Observations of stemwood biomass of LDS trees at a reference age of 75 years (Bsw75,LDS) increased by 154 to 321% over 1901–2001 depending on the method of trend estimation. Simulations from a calibrated individual‐based Growth and Yield model—forced with varying degrees of hypothetical trend in tree growth—were used to estimate the proportion of trend that could be attributed to intrinsic factors, including artefacts introduced by sampling from LDS trees instead of from the population of trees. Imposing no time trend in simulated tree growth, stemwood biomass of 75‐year‐old LDS trees (Bsw75,LDS,Model) increased by 63% (41 to 85% CI). We conclude that the remaining variation in growth of LDS trees (154 to 321% minus 63% = 91 to 258%) can be attributed to net extrinsic forcing. The scaling relationship between LDS and population trees further suggested that stemwood biomass growth of the population (Gsw75,POP) increased by 47 to 82%. By accounting for both natural dynamics and artefacts of the sampling design in estimation of net intrinsic forcing, we gained confidence that growth rate of black spruce trees across Canada increased significantly over 1901–2001. While growth enhancement is consistent with beneficial effects of increasing levels of reactive nitrogen, carbon dioxide, and warming, there remains uncertainty in the degree that applied procedures fully account for known sampling artefacts.

BLADDER RECONSTRUCTION DURING SEPARATION OF A CONJOINT TWIN ISCHIOPAGUS TRIPUS

Objective: Conjoined twins represent one of the rarest congenital anomalies occurring with a varying incidence of about approximately 1 : 50.000 - 1 : 200.000 births. Ischiopagus conjoined twinning (Fuse at the hip region) is even rare representing only 6% of all conjoined twins. Here we report our experience in lower urinary tract reconstruction during separation of a conjoined twin ischiopagus tripus in Hasan Sadikin Hospital, Bandung. Case(s) Presentation: Two years old female conjoined twins, weighing in total of 8 kilograms, were brought to our hospital. The twins were fused at the lower halves of their bodies with two separate lower limbs at the right side and a fused left lower limb. External genitalia were absent. From CT Angiography we found four kidneys, two in each child with two separate bladders, with right ureter of baby A and left ureter of baby B enter the right bladder, while left ureter of baby A and right ureter of baby B enter the left bladder. There was one cloaca that drains urine and feces. During the separation surgery, we performed ureteroneocystostomy and temporary ureteral stenting, followed by cystostomy. The pediatric surgeon performed bowel separation by stapling technique, pelvic wall separation, ileostomy, and pelvic floor reconstruction. The orthopedic surgeon performed femur separation, pelvic floor reconstruction, reconstruction of the pelvic ring, and femur reconstruction. The patients underwent defect closure, which performed by plastic surgeon. The operation was successful, without any complication to the kidney and the urinary tract of both babies. Discussion: Ischiopagus conjoined twins are the most complex conjoined twins and occur in only 6% of all conjoined twin cases. Ischiopagus is usually located along the axis with the head located on the opposite side. This case usually has one umbilicus and the two bodies are fused below this level, the union occurs in the lower abdomen and the pelvis. The internal organs that usually coalesce in cases of ischiopagus conjoined twins are liver, lower gastrointestinal, and genitourinary. The fused gastrointestinal part is the ileo-colic part of terminal ileum (Meckel's diverticulum). Conclusion: The separation of conjoined twin is a unique challenge due to its complex anatomy and physiology. Although advancement in imaging and monitoring has improved the survival rate separation can be successfully achieved only with meticulous planning and team work.

Reconstruction of pelvic ring, using the metal polymer еndoprosthesis after radical internal resection of pelvis

Objective. Investigation of the treatment results and quality of life in the patients, suffering pelvic bones tumors after radical surgical interventions.
 Маterials and methods. Results of treatment of 28 patients after organ-preserving operations and of 26 patients after interventions with the lower extremity excision were analyzed.
 Results. Median index of the lower extremity function in accordance to the MTS scale after resection have constituted (61.06 ± 15.83)%. The quality of life indices in accordance to FIM questionnaire in the patients after organ-preserving operations - (110.85 ± 13.49) points and the extremity amputation - (106.73 ± 11.97) points did not differ essentially (р = 0.12 in accordance to Mann-Whitney). The pain syndrome degree in accordance to visual-analogue scale in the patients after organ-preserving operations was estimated at average in (1.82 ± 1.56) points, after the extremity amputation - at average in (1.42 ± 0.58) points, what did not differ essentially (р = 0.6 in accordance to Mann-Whitney). The implants survival in 1 mo have constituted (60.7 ± 9.2)%, in one year - (53.6 ± 9.2)%.
 Conclusion. The pelvic ring reconstruction, using metal polymer construction constitutes a secure method. It is possible to improve the quality of life after performance of internal resection of pelvic bones with the extremity preservation, using individualization of the patients selection for performance of such interventions.

Reconstruction with a 3D-printed prosthesis and internal fixation with novel four-rod technique after en bloc resection of meningiomas in the lumbosacral region (l5-s3) without rectum/bladder function sacrifice: technical case report

Spinal meningiomas are rare in the lumbosacral region. The best solution is complete tumor resection. However, how to preserve the patient?s rectum/bladder function after en bloc resection is still a considerable challenge, even without spinopelvic reconstruction. The use of the three-dimensional (3D) printing technique may simplify it. The final step after restoration is the establishment of rigid fixation. The purpose of this article was to present a case of lumbosacral meningiomas treated by en bloc resection, 3D-printed prosthesis reconstruction, and fixation with pedicle screws and cortical bone trajectory screws. A 35-year-old woman has suffered from lumbosacral and two legs pain for two months. During the previous month, she limped, and her strength was 4/5 in both legs. Magnetic resonance imaging (MRI) revealed space-occupying lesions from the lumbar 5 (L5) to sacral 3 (S3) vertebral bodies. The previous biopsy confirmed the lesions were spinal meningiomas. The patient underwent an en bloc resection followed by 3D-printed prosthesis reconstruction and internal fixation with a novel technique. The surgery was successful, and the patient recovered well postoperatively according to follow-up examination. En bloc resection of L5-S3 meningiomas without rectum/bladder function sacrifice is a feasible procedure, and 3D-printed prosthesis provides an alternative method for the reconstruction of the spinopelvic ring. The rigid fixation construct using the novel four-rod technique could develop strong bony fusion.

Event reconstruction of free-streaming data for the RICH detector in the CBM experiment

The Compressed Baryonic Matter (CBM) experiment is a dedicated heavy ion collision experiment at the FAIR facility. It will be one of the first HEP experiments which works in a triggerless mode: data received in the DAQ from the detectors will not be associated with events by a hardware trigger anymore. All raw data within a giventime period will be collected continuously in containers, so-called time-slices. The task of the reconstruction algorithms is to create events out of this raw data stream. In this contribution, the optimization of the reconstruction software in the RICH detector to the free-streaming data flow is presented. The implementation of ring reconstruction algorithms which use time measurements of the hits as an additional parameter is discussed.

Effect of Deformity and Malunion of the Anterior Pelvic Ring

Pelvic fractures are common after high-energy trauma and are often associated with ligamentous injury. Treatment is guided by assessing stability of the pelvic ring, and unstable injuries frequently require surgery to achieve a desirable outcome. Assessment of pelvic ring stability is often possible with physical examination and standard imaging studies (plain radiographs and computed tomography); however, these "static" imaging modalities may not adequately identify dynamically unstable pelvic injuries that require surgery. Cadaveric and clinical data suggest that the injured pelvis may recoil significantly from the point of maximal displacement, and some unstable injuries may not be recognized until patients present with clinical symptoms. This article presents the case of a patient who sustained a minimally displaced pelvic ring injury that was stable on bedside examination and static imaging, but ultimately was unstable. She developed a substantial pelvic malunion with significant pain and activity limitations. The patient subsequently underwent successful pelvic ring reconstruction, and she remains asymptomatic at 2 years.

Upshifting the Ipsilateral Proximal Femur May Provide Satisfactory Reconstruction of Periacetabular Pelvic Bone Defects After Tumor Resection.

Pelvic ring reconstruction after resection of pelvic malignancies or aggressive benign tumors remains challenging, especially when the tumor invades periacetabular bone, resulting in a Type II resection as classified by Enneking and Dunham (removal of part or all of the acetabulum). Although numerous treatment approaches are in use, none is clearly superior to the others. An alternative involving use of the ipsilateral proximal femur as an autograft has not been well characterized, so we present our preliminary experience with this approach. (1) What were the oncologic outcomes after using an ipsilateral proximal femur autograft for reconstruction after Type II pelvic resection in a small series of patients who underwent this reconstructive approach? (2) What were the Musculoskeletal Tumor Society (MSTS) scores after this reconstruction? (3) What complications were observed? Between October 2006 and May 2016, we treated 67 patients with Type II malignant or aggressive benign tumors of the ilium. Of those, we used an ipsilateral proximal femur and a prosthesis as a reconstruction method for 11 patients with pelvic tumors. In general, we performed this approach in young or middle-aged patients with primary malignant or aggressive benign tumors involving pelvic area II and in whom the tumor did not invade the hip. The method used for resection of pelvic tumors included osteotomy of the femoral shaft, harvesting the proximal femur as a graft. The length of the femoral graft was determined by the extent of the pelvic defect. The proper placement was selected after a comparison of the proximal femur and the pelvic defect. A curved reconstruction plate and cancellous bone screws were used for pelvic fixation. The operative duration and total blood loss were recorded. Of the 11 patients who underwent this approach, all but one had at least 2 years of followup unless death occurred earlier, and all but one have been seen within the last year for evaluation. Functional outcomes were assessed using the MSTS scoring system. Local recurrence, metastases, and deaths were recorded as were complications including infection, bone nonunion, mechanical failure and sciatic nerve palsy. The followup was a mean of 37 months (range, 13-96 months). One patient was lost to followup. Three patients died of disease owing to local recurrence or lung metastasis. The other seven patients lived without evidence of tumor. The main complications included mechanical failure in two patients, nonunion in one patient, infection in two patients, and sciatic nerve palsy in one patient. The median MSTS function score was 70% (21 of 30 points; range, 11-25 points). Our preliminary results show that this technique of using the ipsilateral proximal femur may be an alternative method for reconstruction of pelvic bone defects after tumor resection. Even with this short followup, complications were common, but short-term function appears to be comparable to studies of other options. Longer term followup with more patients is necessary to confirm our results. Level IV, therapeutic study.

Opening two benzene rings on trichalcogenasumanenes toward high performance organic optical-limiting materials.

Two flanking benzene rings on trichalcogenasumanenes (1a/1b) were opened upon oxidation, and the successive ring reconstruction afforded donor-acceptor type polycycles containing diimide units (3a/3b). 3a and 3b show excellent optical-limiting properties superior to C60.

Thermal conductivity of electron-irradiated graphene

We report results of a systematic analysis of thermal transport in electron-irradiated, including irradiation-induced amorphous, graphene sheets based on nonequilibrium molecular-dynamics simulations. We focus on the dependence of the thermal conductivity, k, of the irradiated graphene sheets on the inserted irradiation defect density, c, as well as the extent of defect passivation with hydrogen atoms. While the thermal conductivity of irradiated graphene decreases precipitously from that of pristine graphene, k0, upon introducing a low vacancy concentration, c < 1%, in the graphene lattice, further reduction of the thermal conductivity with the increasing vacancy concentration exhibits a weaker dependence on c until the amorphization threshold. Beyond the onset of amorphization, the dependence of thermal conductivity on the vacancy concentration becomes significantly weaker, and k practically reaches a plateau value. Throughout the range of c and at all hydrogenation levels examined, the correlation k = k0(1 + αc)−1 gives an excellent description of the simulation results. The value of the coefficient α captures the overall strength of the numerous phonon scattering centers in the irradiated graphene sheets, which include monovacancies, vacancy clusters, carbon ring reconstructions, disorder, and a rough nonplanar sheet morphology. Hydrogen passivation increases the value of α, but the effect becomes very minor beyond the amorphization threshold.

Temperature Covariance in Tree Ring Reconstructions and Model Simulations Over the Past Millennium

AbstractSpatial covariance in the simulated temperature evolution over the past millennium has been reported to exceed that of multiproxy‐based reconstructions. Here we use tree ring‐based temperature reconstructions and state‐of‐the‐art climate model simulations to assess temporal changes in Northern Hemisphere intercontinental temperature covariance during the last 1000 years. Tree ring‐only approaches reveal stronger agreement with model simulations compared to multiproxy networks. Although simulated temperatures exhibit a substantial spread among individual models, intercontinental temperature coherency is mainly driven by the cooling of large volcanic eruptions in 1257, 1452, 1600, and 1815 Common Era. The coherence of these synchronizing events appears to be elevated in several climate simulations relative to their own unforced covariance baselines and in comparison to the proxy reconstructions. This suggests that some models likely overestimate the amplitude of abrupt summer cooling in response to volcanic eruptions, particularly at larger spatial scales.

Molecular basis for the unusual ring reconstruction in fungal meroterpenoid biogenesis

Trt14 from Aspergillus terreus is involved in unusual skeletal reconstruction during the biosynthesis of the fungal meroterpenoid terretonin. Detailed in vitro characterization revealed that this novel multifunctional enzyme catalyzes not only the D-ring expansion via intramolecular methoxy rearrangement, but also the hydrolysis of the expanded D-ring. The X-ray crystal structures of Trt14, in complex with substrate or product, and two Trt14 homologs, AusH and PrhC from Aspergillus nidulans and Penicillium brasilianum, respectively, indicated similar overall structures to those of the NTF2-like superfamily of enzymes, despite lacking sequence and functional similarities. Moreover, we gained structural insight into the mechanism of the Trt14-catalyzed ring reconstruction from the in-crystal enzyme reaction and site-directed mutagenesis to show that this reaction involves sequential ester bond cleavage and formation. Structural comparison of Trt14 and its homologs suggests that the enzymes in this new superfamily employ similar acid-base chemistry to diversify the molecular architecture of fungal meroterpenoids.

Tree ring reconstructed rainfall over the southern Amazon Basin

AbstractMoisture sensitive tree ring chronologies of Centrolobium microchaete have been developed from seasonally dry forests in the southern Amazon Basin and used to reconstruct wet season rainfall totals from 1799 to 2012, adding over 150 years of rainfall estimates to the short instrumental record for the region. The reconstruction is correlated with the same atmospheric variables that influence the instrumental measurements of wet season rainfall. Anticyclonic circulation over midlatitude South America promotes equatorward surges of cold and relatively dry extratropical air that converge with warm moist air to form deep convection and heavy rainfall over this sector of the southern Amazon Basin. Interesting droughts and pluvials are reconstructed during the preinstrumental nineteenth and early twentieth centuries, but the tree ring reconstruction suggests that the strong multidecadal variability in instrumental and reconstructed wet season rainfall after 1950 may have been unmatched since 1799.

Aromatic metamorphosis: conversion of an aromatic skeleton into a different ring system.

Aromatic skeletons are generally regarded as being uncleavable because of their aromatic stabilization energy. Compared to exocyclic functionalizations of aromatic compounds, much less attention has been paid to substitutions of endocyclic atoms in aromatic cores through partial disassembly of the cyclic skeletons and subsequent ring reconstruction. In this Feature Article, we describe our endeavours to establish "aromatic metamorphosis", where general aromatic compounds such as dibenzothiophenes, dibenzofurans, and benzofurans are transformed into different ring systems using a multi-step strategy or ideally in one step.

Negative feedback adjustment challenges reconstruction study from tree rings: A study case of response of Populus euphratica to river discontinuous flow and ecological water conveyance

Drought stress changes the relationship between the growth of tree rings and variations in ambient temperature. However, it is not clear how the growth of trees changes in response to drought of varying intensities, especially in arid areas. Therefore, Tree rings were studied for 6years in Populus euphratica to assess the impacts of abrupt changes in environment on tree rings using the theories and methods in dendrohydrology, ecology and phytophysiology. The width of tree rings increased by 8.7% after ecological water conveyance downstream of Tarim River compared to that when the river water had been cut off. However, during intermediate drought, as the depth of the groundwater increases, the downward trend in the tree rings was reversed because of changes in the physiology of the tree. Therefore, the growth of tree rings shows a negative feedback to intermediate drought stress, an observation that challenges the homogenization theory of tree ring reconstruction based on the traditional methods. Owing to the time lag, the cumulative effect and the negative feedback between the growth of tree rings and drought stress, the reconstruction of past environment by studying the patterns of tree rings is often inaccurate.Our research sets out to verify the hypothesis that intermediate drought stress results in a negative feedback adjustment and thus to answers two scientific questions: (1) How does the negative feedback adjustment promote the growth of tree rings as a result of intermediate drought stress? (2) How does the negative feedback adjustment lower the accuracy with which the past is reconstructed based on tree rings? This research not only enriches the connotations of intermediate disturbance hypothesis and reconstruction theory of tree rings, but also provides a scientific basis for the conservation of desert riparian forests worldwide.