University of Ulsan Open Access Korea
Not a member yet
17799 research outputs found
Sort by
Clinical impact and potential utility of non-enhanced computed tomography performed immediately after transarterial chemoembolization for hepatocellular carcinoma
No full textBackground: Intratumoral lipiodol deposition following transarterial chemoembolization (TACE) is associated with the prognosis of hepatocellular carcinoma (HCC) patients. However, there is insufficient evidence regarding the actual clinical significance of the imaging tests conducted to evaluate the lipiodol uptake after TACE. This study evaluates the clinical impact and potential utility of performing immediate post-TACE non-enhanced computed tomography (NECT) on the treatment of HCC.
Methods: This retrospective study at a tertiary referral center included patients undergoing their first session of conventional TACE for initial treatment of HCC from November 2021 to December 2022 with available immediate post-TACE NECT. Patients were categorized based on lipiodol uptake into Cohorts A (incomplete uptake with additional treatment before the first follow-up 1 month after TACE), B incomplete uptake without additional treatment before first follow-up), and C (complete uptake). Survival curves for the time to progression (TTP) were estimated using the Kaplan-Meier method and were compared by using the log-rank test.
Results: Out of 189 patients, 58 (29.6%) showed incomplete lipiodol uptake; 2 in Cohort A and 56 in Cohort B. Cohort C included 131 patients (69.3%). Cohort B had the highest rate of residual viable tumor (48.2%) 1 month after TACE, compared to the other cohorts (0% in Cohort A and 32.1% in Cohort C). The median TTP of Cohort B was 7.9 months [95% confidence interval (CI): 4.6-15.7 months], significantly shorter than the 15.4 months (95% CI: 10.9-20.9 months) for Cohort C (P=0.03). During follow-up, no progression occurred in Cohort A.
Conclusions: Assessment of lipiodol uptake by performing immediate post-TACE NECT can stratify HCC patients and facilitate early prediction of therapeutic response. Identifying suboptimal lipiodol uptake immediately after TACE can aid future treatment adjustments and potentially improving oncologic outcomes
Exposure-response analysis using time-to-event data for bevacizumab biosimilar SB8 and the reference bevacizumab
No full textPurpose: This analysis aimed to characterize the exposure-response relationship of bevacizumab in non-small-cell lung cancer (NSCLC) and evaluate the efficacy of SB8, a bevacizumab biosimilar, and Avastin®, the reference bevacizumab sourced from the European Union (EU), based on the exposure reported in a comparative phase III efficacy and safety study (EudraCT, 2015-004026-34; NCT02754882). Materials and methods: The overall survival (OS) and progression-free survival (PFS) data from 224 patients with steady-state trough concentrations (Css,trough) were analyzed. A parametric time-to-event (TTE) model was developed using NONMEM®, and the effects of treatments (SB8 and bevacizumab-EU) and patient demographic and clinical covariates on OS and PFS were evaluated. Simulations of median OS and PFS by bevacizumab Css,trough were conducted, and concentrations required to achieve 50% and 90% of the maximum median TTE were computed. Results: A log-logistics model with Css,trough best described the OS and PFS data. Treatment was not a predictor of the hazard for OS or PFS. Simulations revealed steep exposure-response curves with a phase of rapid rise before saturating to a plateau. The median Css,trough values of SB8 and bevacizumab-EU reported from the clinical study were on the plateaus of the exposure-response curves. The concentrations required to achieve 50% and 90% of the maximum effect were 82.4 and 92.2 μg/mL, respectively, for OS and 79.7 and 89.1 μg/mL, respectively, for PFS. Conclusion: Simulations based on the constructed TTE models for OS and PFS have well described the exposure-response relationship of bevacizumab in advanced NSCLC. The analysis demonstrated comparable efficacy between SB8 and bevacizumab-EU in terms of OS and PFS based on their exposure levels
Canakinumab Versus Placebo in Combination With First-Line Pembrolizumab Plus Chemotherapy for Advanced Non-Small-Cell Lung Cancer: Results From the CANOPY-1 Trial
No full textPurpose: The addition of checkpoint inhibitors to first-line treatment has prolonged survival of patients with non-small-cell lung cancer (NSCLC), but prognosis remains poor, with new treatment options needed. Canakinumab, a human, monoclonal anti-interleukin (IL)-1β antibody, has potential to enhance the activity of PD-L1 inhibitors and chemotherapy (CT) by inhibiting protumor inflammation.
Methods: CANOPY-1 was a phase III, randomized, double-blind study comparing canakinumab (200 mg subcutaneously once every 3 weeks) versus placebo, both combined with pembrolizumab (200 mg intravenously once every 3 weeks) and platinum-based doublet CT, as first-line treatment for advanced/metastatic NSCLC without EGFR or ALK mutations. The primary end points were progression-free survival (PFS) and overall survival (OS). The secondary endpoints included overall response rate, safety, and patient-reported outcomes.
Results: Overall, 643 patients were randomly assigned to canakinumab (n = 320) or placebo (n = 323). With a median study follow-up of 6.5 months, the median PFS was 6.8 months with canakinumab versus 6.8 months with placebo (hazard ratio [HR], 0.85; 95% CI, 0.67 to 1.09; P = .102). With a median study follow-up of 21.2 months, the median OS was 20.8 months with canakinumab versus 20.2 months with placebo (HR, 0.87; 95% CI, 0.70 to 1.10; P = .123). No unexpected safety signals were observed for canakinumab combination. Infection rates were comparable between treatment and control arms. A higher frequency of neutropenia and ALT increase (grade ≤2) were reported in the treatment arm. Higher baseline C-reactive protein and IL-6 levels were associated with shorter PFS and OS. Patients treated with canakinumab had clinically meaningful delays in deterioration of lung cancer symptoms, including chest pain and coughing per LC13 and dyspnea per LC13 and C30.
Conclusion: The addition of canakinumab to first-line pembrolizumab and CT did not prolong PFS or OS in patients with NSCLC
Studies on Shape-Controlled Nanoparticles for Enhanced Electrocatalytic Reaction
No full text화석연료로 인한 환경오염 문제가 심각해지고, 자원 고갈 위기에 맞아 새로운 에너지에 대한 연구 필요성은 이전보다 대두되고 있다. 새로운 에너지는 지속 가능한 미래를 위한 형태를 띄고 있어야 하기에 풍부한 자원을 활용하고, 환경 오염을 최소화할 필요가 있다. 이러한 관점에서 전기화학을 통한 에너지 전환은 물, 산소, 수소, 이산화탄소 등 풍부한 자원을 이용해 이루어지기에 이는 재생가능한 에너지원으로 유망하다. 전기화학을 통한 에너지 전환의 종류에는 수소 생산, 산소 환원, 알코올 산화와 같은 연료전지 반응과 이산화탄소의 환원에 의한 탄화수소 생산을 포함하여 다양한 반응들이 있다.
이러한 전기화학 반응에 필요한 활성화 에너지를 낮추고 전체 반응의 효율을 향상시키기 위해서는 전극에 사용되는 촉매가 중요하다. 촉매의 표면에서 전기화학 반응이 빠르게 일어나기 위해서는 반응물과 촉매 사이의 흡착 세기가 조절되어야 한다. 반응물이 촉매 표면에 원활하게 흡착하여 반응하고 난 뒤에 생성물로 전환되어 쉽게 떨어져야하기 때문이다. 따라서 촉매와 반응물 사이의 흡착 특성을 조절하는 것은 촉매 연구에서 중요한 부분이며 이를 달성하기 위해 다양한 형태의 합금과 형상 조절이 필요하다. 합금을 통해서는 구성 성분간 전기음성도 차이, 격자상수 차이 등에 의해 전자구조의 변화를 유도할 수 있으며 변화된 전자구조에 의해 흡착물과의 흡착 특성이 변화할 수 있다. 또한 형상 조절을 통해 표면 원자 구조에 변화가 생기면 표면 원자의 배위수가 줄어듦에 따라 반응물과의 흡착특성 변화가 가능하다.
촉매의 활성은 위와 같이 반응물과 촉매 사이 흡착 특성 조절을 통해 이룰 수 있으며 또 다른 방법은 활성 부위를 증가시키는 것이다. 촉매의 활성 부위를 증가시키기 위해서 촉매 자체의 형상 조절을 통해 부피 대 표면적을 극대화할 수 있다. 나노시트와 같은 이차원 구조나 다공성 구조로 촉매를 디자인함으로써 원자의 활용성을 극대화하고 반응물과 생성물의 빠른 이동을 유도함으로써 촉매의 활성을 증가시킬 수 있는 것이다.
이 논문에서는 형상 및 합금의 조성 조절을 통해서 촉매를 합성하고 전기화학 반응에 활용하였다. 이를 통해서 촉매의 형상 및 조성이 전기화학적 활성에 큰 영향을 미치는 것을 확인할 수 있었다.|The increasing environmental pollution resulting from fossil fuel usage and the looming threat of resource depletion have heightened the need for research into alternative energy sources. From this perspective, electrochemical energy conversion, using abundant resources such as water, oxygen, hydrogen, and carbon dioxide, emerges as a promising avenue for sustainable energy production. Various electrochemical reactions fall under this category, including hydrogen production, oxygen reduction, alcohol oxidation in fuel cells, and carbon dioxide reduction for hydrocarbon generation.
To enhance the efficiency and reduce the activation energy required for these electrochemical reactions, the choice of catalysts used at the electrodes becomes crucial. For efficient electrochemical reactions, it is essential that reactants are adequately adsorbed on the catalyst's surface, facilitating rapid reactions, followed by the easy release of the products. Therefore, controlling the adsorption characteristics between catalyst and reactants is a pivotal aspect of catalyst research. Achieving this necessitates the utilization of different forms of catalysts, including alloys and shape manipulation.
Alloys can induce changes in electronic structure due to differences in electronegativity between their components and lattice constants, thereby altering the adsorption characteristics of the catalyst surface. Furthermore, by manipulating the catalyst's shape, changes in the surface atomic structure can be achieved, allowing for adjustments in adsorption properties as the coordination number of surface atoms is reduced.
Modulating the adsorption characteristics between reactants and catalysts, as described above, contributes to enhancing catalyst activity. Another approach involves increasing the active sites of the catalyst by controlling its shape. By controlling the morphology of catalyst, it is possible to maximize the surface area relative to its volume, thus augmenting its catalytic activity. Designing catalysts with two-dimensional structures like nanosheets or porous structures maximizes the utilization of atoms and enhances the catalytic activity by facilitating rapid movement of reactants and products.
In this paper, we synthesized catalysts by controlling both shape and alloy composition and applied them to electrochemical reactions. Through these experiments, we confirmed that the shape and composition of the catalyst significantly impact its electrochemical activity.
In summary, electrochemical energy conversion, driven by catalyst research involving adsorption control and the augmentation of active sites through shape manipulation and alloy composition, offers great promise as a sustainable energy source, particularly in the context of mitigating environmental pollution and addressing resource scarcity.Maste
The Relationship Between Brain Activation for Taking Others' Perspective and Interoceptive Abilities in Autism Spectrum Disorder: An fMRI Study
No full textObjectives: In this functional magnetic resonance imaging study, we aimed to investigate the differences in brain activation between individuals with autism spectrum disorder (ASD) and typically developing (TD) individuals during perspective taking. We also examined the association between brain activation and empathic and interoceptive abilities.
Methods: During scanning, participants from the ASD (n=17) and TD (n=22) groups were shown pain stimuli and asked to rate the level of the observed pain from both self- and other-perspectives. Empathic abilities, including perspective taking, were measured using an empathic questionnaire, and three dimensions of interoception were assessed: interoceptive accuracy, interoceptive sensibility, and interoceptive trait prediction errors.
Results: During self-perspective taking, the ASD group exhibited greater activation in the left precuneus than the TD group. During other-perspective taking, relative hyperactivation extended to areas including the right precuneus, right superior frontal gyrus, left caudate nucleus, and left amygdala. Brain activation levels in the right superior frontal gyrus while taking other-perspective were negatively correlated with interoceptive accuracy, and those in the left caudate were negatively correlated with perspective taking ability in the ASD group.
Conclusion: Individuals with ASD show atypical brain activation during perspective taking. Notably, their brain regions associated with stress reactions and escape responses are overactivated when taking other-perspective. This overactivity is related to poor interoceptive accuracy, suggesting that individuals with ASD may experience difficulties with the self-other distinction or atypical embodiment when considering another person's perspective
Risk-Preventive Intelligence Activities of the Intelligence Police and Legislative Control
No full text우리 사회의 위험이 고도화되면서 공공안녕의 위험을 예방해야 하는 경찰의 부담이 증가하고 있다. 이에 따라, 정보경찰도 「경찰관직무집행법」상 범죄, 재난, 공공갈등 등 공공안녕에 대한 위험의 예방과 대응을 위한 정보활동을 요구받고 있다. 이러한 시대적 요구에도 불구하고, 2018년 경찰개혁위원회의 ‘정보경찰 권고안’에서 시작된 정보경찰 조직 폐지와 업무 이관을 요구하는 목소리가 여전한 상황이다. 「국가경찰과 자치경찰의 조직 및 운영에 관한 법률」·「경찰관직무집행법」의 개정, 「경찰관의 정보수집 및 처리 등에 관한 규정」의 제정 등 입법적 통제장치가 실효적으로 작동하고 있고 현장 정보활동에도 실질적인 변화가 나타나고 있다는 사실이 외면받고 있기 때문이다. 이제 미래를 바라보고 정보경찰이 위험예방적 정보활동에 집중할 수 있도록 법제도적 정비가 필요한 시점이다. 특히, 정보활동의 대상으로서의 공공갈등의 개념을 조속히 마련하여 법령에 반영하고, 기본권 제한적 요소를 발굴해 찾아내는 노력이 필요하다.
As risks in our society become more complex, the burden on the police to prevent threats to public safety is increasing. Accordingly, intelligence police are also being called upon to conduct intelligence activities aimed at preventing and responding to risks related to public safety, such as crime, disasters, and public conflicts, as per the Police Duties Execution Act. Despite these demands of the times, there are still calls for the abolition of the intelligence police and the transfer of their duties, which began with the ‘Recommendations for Intelligence Police’ issued by the Police Reform Committee in 2018. This is because the legislative control measures, such as the amendment of the Police Act and the Police Duties Execution Act and the enactment of regulations regarding the collection and processing of information by police officers, are functioning effectively, and there are tangible changes in field intelligence activities-facts that are being overlooked. It is now time to look toward the future and reform the legal and institutional framework so that the intelligence police can focus on preventive intelligence activities. In particular, it is necessary to promptly define the concept of public conflict as a target of intelligence activities and reflect it in the laws, while also making efforts to identify and address elements that restrict fundamental rights
Sinonasal Organizing Hematoma: Demographics, Diagnosis, and Treatment Outcomes of 112 patients
No full textIntroduction: Sinonasal organizing hematoma (OH) is a rare, nonneoplastic lesion that often presents with epistaxis, a reddish mass, and destruction of the involved sinonasal structures. Due to its rarity, the demographics, diagnostic modalities, treatment strategies, and outcomes have not yet been studied in a large, long-term study.
Materials and methods: Retrospect cohort of 112 sinonasal OH patients treated between 1997 and 2020 in a tertiary, university hospital were evaluated. Demographics, systemic comorbidities, sinonasal surgery history, serum laboratory tests, radiological findings, and treatment results were collected. The present study aimed to assess the accuracy of preoperative computed tomography (CT), Gadolinum-enhanced magnetic resonance (MR), and punch biopsies in detecting sinonasal OH as the most likely diagnosis. In addition, incidental differences by age and year of diagnosis were calculated using the Poisson log-linear regression model.
Results: The median age was 44, and 58% were male. Fewer than 20% of these cases had a chronic systemic comorbidity, bleeding tendency, or sinonasal surgery history. MR had the highest accuracy of (87%) to detect sinonasal OH as the most likely diagnosis, compared with contrast-enhanced-CT (53%), punch biopsy (49%), and non-enhanced-CT (16%) (all <0.05). Sinonasal OH incidence did not vary by age, but the yearly rate significantly increased by 1.05 times over 23 years (p < 0.05). Notably, 84% of 112 patients received surgical removal through the assistance of an endoscope, and none had substantial bleeding without preoperative embolization.
Conclusion: Sinonasal OH was observed regardless of age, sex, systemic comorbidities, bleeding tendency, prior sinonasal surgery, or trauma. Preoperative MR gives the highest accuracy for detecting this disease. Sinonasal OH may be safely managed with endoscopic-assisted surgery removal without embolization
Study on the signaling mechanism of cell proliferation inhibition by eribulin in multiple myeloma cells
No full text배경: 다발골수종은 혈액암의 한 종류로 백혈구 중 B 림프구의 최종 성숙단계인 형질세포가 악성으로 전환되어 골수에서 비정상적으로 분화 및 증식하는 질환이다. 감염에 대항하여 신체를 보호할 수 있는 항체를 생산하는 정상적인 형질세포와 달리 다발골수종은 단클론단백이라고 하는 M 단백을 생성하게 되고 혈액이나 소변에서 발견되는 것이 특징이다. 다발골수종을 치료하기 위해 화학항암요법과 면역치료법 등이 사용되고 있지만 다양한 부작용과 높은 재발율과 같은 이유로 여전히 완치가 어려운 질환이다. 에리불린은 halichondrin B 에서 얻어진 합성 케톤 유사체로 전이성 유방암이나 지방육종에 사용되고 있는 항암제이다. 그러나, 다발골수종에서 에리불린에 효과에 대해서는 아직 연구된 바가 없다. Signal transducers and activators of transcription 3 (STAT3)는 대부분의 암에서 종양 발생 및 진행에 기여하는 종양유전자로 다발골수종에서는 세포사멸을 억제하거나 골수유래억제세포를 활성화함으로써 다발골수종 진행에 관여한다. 따라서, 본 연구에서는 에리불린이 다발골수종 세포에서 STAT3 신호 전달 경로를 표적으로 하여 항종양효과가 있는지 확인하며 다발골수종의 치료제로써 어떤 효능을 보이는지에 대한 연구를 수행하였다.
방법: 다발골수종 세포주인 RPMI-8226, U266B1 에 에리불린을 72 시간 동안 처리한 후, MTS assay 와 BrdU assay 를 통해 세포 생존율과 세포 증식률을 확인하였다. Annexin V 염색을 통해 세포사를 확인하였고 caspase 활성도, Dioc6(3) 염색과 이와 관련된 단백질 발현을 통해 세포 사멸 경로를 분석하였다. STAT3 신호 전달 경로와 그 하위 단백질 발현과 STAT3-siRNA 형질주입을 통해 이와 관련된 단백질의 발현을 Western blot 을 통해 분석하였다.
결과: 다발골수종 세포주인 RPMI-8226 와 U266B1 에서 에리불린을 농도별로 72 시간 동안 처리한 후, 세포 생존율과 세포 증식률이 농도의존적으로 감소하는 것을 확인하였다. RPMI-8226 세포에서 세포사 확인을 위해 Annexin V 양성 세포 비율을 유세포 분석을 통해 알아본 결과, 에리불린의 농도가 높아질수록 세포사가 발생하는 것을 확인하였다. Caspase 활성도와 관련 단백질인 Cleaved caspase -3, -7, -9 및 PARP-1 발현은 에리불린 농도가 높아짐에 따라 증가하는 것을 확인하였다. 또한, Dioc6(3) 결과가 농도의존적으로 감소함에 따라 미토콘드리아 막 전위가 감소하는 것을 확인하였고 세포질 방향으로 Cytochrome C 의 방출량이 증가하는 것을 확인하였다. 미토콘드리아 경로와 관련된 단백질인 Bcl-2 의 발현은 감소하고, Bax 와 Bak 의 발현은 증가하는 것을 확인하였다. 또한, 에리불린을 처리했을 때, p-STAT3 와 STAT3 의 발현이 감소했으며 이들의 하위 단백질인 Bcl-xL, Mcl-1, c-Myc, Cyclin D1, Cyclin D3 의 발현 또한 감소하는 것을 확인하였다.
결론: 에리불린은 다발골수종 세포주인 RPMI-8226 세포에서 STAT3 신호 기전이 관여하여 세포증식을 억제하고 caspase 의 활성과 미토콘드리아의 막 전위 감소를 통해 세포사멸을 유도한다는 것을 확인하였다. 이러한 결과를 통해 에리불린이 다발골수종의 새로운 치료 약물로 사용될 수 있는 가능성을 제시하였다.|Background: Multiple myeloma is a type of blood cancer in which plasma cells, the final maturity stage of B lymphocytes among white blood cells, are converted to malignant, causing abnormal differentiation and proliferation in the bone marrow. Unlike normal plasma cells that produce antibodies that can protect the body against infection, multiple myeloma produces an M protein called a monoclonal protein and this M protein is found in blood or urine. Chemotherapy and immunotherapy are used to treat multiple myeloma, but it is still difficult to cure for various side effects and high recurrence rates. Eribulin is a synthetic macrocyclic ketone analog obtained from halichondrin B and is an anticancer drug used for metastatic breast cancer or adiposarcoma. However, no research has yet been conducted on the effect of eribulin in multiple myeloma. STAT3 is an oncogene that contributes to the development and progression of tumors in most cancers, and in multiple myeloma, it is involved in the progression of multiple myeloma by inhibiting apoptosis or activating bone marrow-derived inhibitory cells. Therefore, in this study, we investigated whether eribulin has anti-tumor effects by targeting the STAT3 signaling pathway in multiple myeloma cells and can serve as a therapeutic agent for multiple myeloma.
Method: Eribulin was treated with RPMI-8226 cells and U266B1 cells, a multiple myeloma cell line, cell survival and proliferation rates were confirmed through MTS assay and BrdU assay. Apoptosis was confirmed through Annexin V staining, and the path of apoptosis was analyzed through caspase activity, Dioc6(3) staining, and related proteins expression. The expression of proteins related to STAT3 signaling pathway and its downstream and expression of related proteins through STAT3-siRNA transfection were confirmed through Western blot analysis.
Results: After Eribulin was treated with RPMI-8226 cells and U266B1 cells for 72 hours at each concentration, it was confirmed that cell survival and cell proliferation rates decreased in a concentration-dependent manner. As a result of confirming the proportion Annexin V-positive cells using flow cytometry, it was confirmed that apoptosis occurs as the concentration of eribulin increased. It was confirmed that caspase activity and the associated proteins cleaved caspase -3, -7, -9, and PARP-1 expression increased as the concentration of eribulin increased. In addition, it confirmed that as the Dioc6(3) results decrease, the mitochondrial membrane potential was decreased in concentration-dependent and that the release of Cytochrome C was increased. When the expression of proteins related to the mitochondrial pathway was confirmed, the expression of Bcl-2 decreased, and the expression of Bax and Bak increased. In addition, the expression of p-STAT3 and STAT3 was reduced, and the expression of downstream proteins Bcl-xL, Mcl-1, c-Myc, Cyclin D1, and Cyclin D3 was also reduced.
Conclusion: In conclusion, its finding showed that eribulin inhibits cell proliferation and induces apoptosis through the activation of caspase and reduction of mitochondrial membrane potential by involving in STAT3 signaling mechanisms in RPMI-8226 cells. These results suggested that eribulin may be used as a new therapeutic drug for multiple myeloma.Maste
Investigation of the combustion characteristics of a dual direct injection fuel (diesel-propane) strategy on a rapid compression expansion machine
No full textFor internal combustion engines, liquid petroleum gas (LPG) is a promising alternative fuel due to its typical specific calorific value. A rapid compression and expansion machine (RCEM) that resembles a compression ignition (CI) engine has been the subject of experimental research using a dual direct injection fuel. For this application, 10 %-100 % diesel-propane (DP) is applied based on the percentage of the low heating value (LHV) with the propane injection timing varying from 0◦ to 40◦ before top dead center and maintaining the diesel injection timing at 10◦ before top dead center (BTDC). The compression ratio was varied between 17 and 19 by adjusting the connecting rod of the RCEM. The outcome indicates that at the compression ratio of 17, propane promoted no auto-ignition. Meanwhile, at a compression ratio (CR) of 19, the auto-ignition was enhanced and occurred earlier as the amount of propane increased. However, a longer ignition delay was produced as the propane fraction was above 60 %. The highest indicated thermal efficiency (ITE) was produced at a propane fraction of 40 % at 40oBTDC. At propane fractions greater than 60 %, the highest efficiency was achieved at 20◦- 30o BTDC start of injection (SOI) of propane for both CR 17 and 19
Modeling sacrifice
No full textRecent evidence suggests that a person’s reciprocity toward others depends on the amount of sacrifice made by others. We develop a reciprocity model that incorporates the concept of sacrifice, defined as the payoff forgone when choosing an action. Our model retains many desirable properties of the existing reciprocity models, while capturing the nuanced psychology of reciprocity. In our model, one’s motivation to reciprocate increases in the size of others’ sacrifice. In two-person games, it can be shown that our model strengthens reciprocity motivation in reciprocity equilibria that are not Nash equilibria under selfish preferences