Hierarchical Distributed Representations for Statistical Language Modeling

Statistical language models estimate the probability of a word occurring in a given context. The most common language models rely on a discrete enumeration of predictive contexts (e.g., n-grams) and consequently fail to capture and exploit statistical regularities across these contexts. In this paper, we show how to learn hierarchical, distributed representations of word contexts that maximize the predictive value of a statistical language model. The representations are initialized by unsupervised algorithms for linear and nonlinear dimensionality reduction [14], then fed as input into a hierarchical mixture of experts, where each expert is a multinomial distribution over predicted words [12]. While the distributed representations in our model are inspired by the neural probabilistic language model of Bengio et al. [2, 3], our particular architecture enables us to work with significantly larger vocabularies and training corpora. For example, on a large-scale bigram modeling task involving a sixty thousand word vocabulary and a training corpus of three million sentences, we demonstrate consistent improvement over class-based bigram models [10, 13]. We also discuss extensions of our approach to longer multiword contexts

Better word alignments with supervised ITG models

This work investigates supervised word align-ment methods that exploit inversion transduc-tion grammar (ITG) constraints. We con-sider maximum margin and conditional like-lihood objectives, including the presentation of a new normal form grammar for canoni-calizing derivations. Even for non-ITG sen-tence pairs, we show that it is possible learn ITG alignment models by simple relaxations of structured discriminative learning objec-tives. For efficiency, we describe a set of prun-ing techniques that together allow us to align sentences two orders of magnitude faster than naive bitext CKY parsing. Finally, we intro-duce many-to-one block alignment features, which significantly improve our ITG models. Altogether, our method results in the best re-ported AER numbers for Chinese-English and a performance improvement of 1.1 BLEU over GIZA++ alignments.

Echocardiographic Guidance During Neonatal and Pediatric Jugular Cannulation for ECMO

Background Internal jugular vein extracorporeal membrane oxygenation (ECMO) cannula position is traditionally confirmed via plain film. Misplaced cannulae can result in need for repositioning and increased morbidity. Echocardiography (ECHO) may be used during cannulation as a more accurate means of guiding cannula position. This study reviews the effect of a protocol encouraging the use of ECHO at cannulation. Methods and materials Single institution retrospective review of patients who received ECMO support using jugular venous cannulation. We compared those who underwent ECHO (ECHO+) at the time of cannulation with those who did not (ECHO−). Results Eighty-nine patients were included: 26 ECHO+, 63 ECHO−. Most ECHO+ patients underwent dual-lumen veno-venous (VV) cannulation (65%); 32% of ECHO− patients had VV support (P = 0.003). There was no difference in the rate of cannula repositioning between the two groups: 8% ECHO+ and 10% ECHO−, P = 0.78. In the VV ECMO subgroup, ECHO+ patients required no repositioning (0/17), while 20% (4/20) of ECHO− VV patients did (P = 0.10). After cannulation, there were 0.58 ECHO studies per patient to verify cannula position in the ECHO+ group compared with 0.22 in the ECHO− group (P = 0.02). Each group had a major mechanical complication: atrial perforation from a guidewire during cannulation in ECHO+ and late atrial perforation from a loose cannula in ECHO−, and there was no difference in minor complications. Conclusions ECHO guidance during neonatal and pediatric jugular cannulation for ECMO did not decrease morbidity or reduce the need for cannula repositioning. ECHO may still be a useful adjunct for precise placement of a dual-lumen VV cannula and during difficult cannulations

Open repair of chronic thoracic and thoracoabdominal aortic dissection using deep hypothermia and circulatory arrest

Background Chronic dissection of the thoracic and thoracoabdominal aorta as sequela of a prior type A or B dissection is a challenging problem that requires close radiographic surveillance and prompt operative intervention in the presence of symptoms or aneurysm formation. Open repair of chronic thoracic and thoracoabdominal aortic dissection using deep hypothermia has been our preferred method to treat this complex pathology. The advantages of this technique include organ and spinal cord protection, the flexibility to extend the repair proximally into the arch, and the ability to limit ischemia to all vascular beds. Methods Open repair of arch by left thoracotomy and descending thoracic and thoracoabdominal aortic pathology using deep hypothermia was performed in 664 patients from 1995 to 2015. A subset of this cohort had chronic thoracoabdominal aortic dissection (n = 196). All nonemergency cases received coronary angiography and echocardiography preoperatively. Significant coronary artery disease or severe aortic insufficiency was addressed before repair of the chronic dissection. In recent years, lumbar drains were placed preoperatively in the most extensive repairs (extents II and III). Important intercostal arteries from T8 to L1 were revascularized with smaller-diameter looped grafts. Multibranched grafts for the visceral segment have been preferred in recent years. Results Mean age of patients was 58 ± 14 years. Men comprised 74% of the cohort. Aortopathy was confirmed in 18% of the cohort. Prior thoracic aortic repair occurred in 57% of patients, and prior abdominal aortic repair occurred in 14% of patients. Prior type A aortic dissection occurred in 44% of patients, and prior type B occurred in 56% of patients. Operative mortality was 3.6%, permanent spinal cord ischemia occurred in 2.6% of patients, permanent hemodialysis occurred in 0% of patients, and permanent stroke occurred in 1% of patients. Reexploration for bleeding was 5.1%, and respiratory failure requiring tracheostomy occurred in 2.6%. Postoperative length of stay was 11.9 ± 9.7 days. Reintervention for pseudoaneurysm or growth of a distal aneurysm was 6.9%. The 1-, 5-, and 10-year survivals were 93%, 79%, and 57%, respectively. Conclusions Open repair of chronic thoracic and thoracoabdominal aortic dissection using deep hypothermia and circulatory arrest has low morbidity and mortality. The need for reintervention is low, and long-term survival is excellent. We believe that open repair continues to be the gold standard in patients who are suitable candidates for surgery

Repair of Thoracic and Thoracoabdominal Mycotic Aneurysms and Infected Aortic Grafts Using Allograft

Background Mycotic aneurysm of the thoracic or thoracoabdominal aorta and infection of thoracic or thoracoabdominal aortic grafts are challenging problems with high mortality. In-situ reconstruction with cryopreserved allograft(CPA) avoids placement of prosthetic material in an infected field and avoids suppressive antibiotics or autologous tissue coverage. Methods Fifty consecutive patients with infection of a thoracic or thoracoabdominal aortic graft or mycotic aneurysm underwent resection and replacement with CPA from 2006 to 2016. Intravenous antibiotics were continued postoperatively for 6 weeks. Long-term suppressive antibiotics were uncommonly used (8 patients). Follow up imaging occurred at 6, 18 and 42 months postoperatively. Initial follow up was 93% complete. Results Males comprised 64% of the cohort. The mean age was 63±14 years. The procedures performed included reoperations in 37, replacement of the aortic root, ascending aorta or transverse arch in 19, replacement of the descending or thoracoabdominal aorta in 27 and extensive replacement of the ascending, arch and descending or thoracoabdominal aorta in 4. Intraoperative cultures revealed most commonly staphylococcus 24%), enterococcus (12%), candida (6%) and gram negative rods (14%). Operative mortality was 8%, stroke 4%, paralysis 2%, hemodialysis 6%, and respiratory failure requiring tracheostomy 6%. Early reoperation for pseudoaneurysm of the CPA was necessary in 4 patients. One, two and five year survival was 84%, 76% and 64%, respectively. Conclusions Radical resection and in-situ reconstruction with CPA avoids placing prosthetic material in an infected field and provides good early and mid-term outcomes. However, early postoperative imaging is necessary given the risk of pseudoaneurysm formation

Evaluating Induced CCG Parsers on Grounded Semantic Parsing

We compare the effectiveness of four different syntactic CCG parsers for a semantic slot-filling task to explore how much syntactic supervision is required for downstream semantic analysis. This extrinsic, task-based evaluation provides a unique window to explore the strengths and weaknesses of semantics captured by unsupervised grammar induction systems. We release a new Freebase semantic parsing dataset called SPADES (Semantic PArsing of DEclarative Sentences) containing 93K cloze-style questions paired with answers. We evaluate all our models on this dataset. Our code and data are available at https://github.com/sivareddyg/graph-parser.Comment: EMNLP 2016, Table 2 erratum, Code and Freebase Semantic Parsing data UR