<?xml version="1.0" encoding="US-ASCII"?>  
<!-- Generated by CompSci Transform (tm) - http://www.compsciresources.com -->    
<!-- Created: Fri Mar 27 00:51:39 UTC 2026 -->  
<xs:schema elementFormDefault="qualified" targetNamespace="http://www.nb.com/20260327" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:ck0000736913="http://www.nb.com/20260327" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:us-types="http://xbrl.us/us-types/2009-01-31" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:dtr="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:xbrli="http://www.xbrl.org/2003/instance">     
  <xs:annotation>   
    <xs:appinfo>  
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      <link:linkbaseRef xlink:type="simple" xlink:href="ck0000736913-20260327_pre.xml" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef"/> 
      <link:linkbaseRef xlink:type="simple" xlink:href="ck0000736913-20260327_def.xml" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef"/>    
    </xs:appinfo>   
  </xs:annotation>    
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>  
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>  
  <xs:import namespace="http://xbrl.sec.gov/oef/2025" schemaLocation="https://xbrl.sec.gov/oef/2025/oef-2025.xsd"/> 
  <xs:import namespace="http://xbrl.sec.gov/oef-rr/2025" schemaLocation="https://xbrl.sec.gov/oef/2025/oef-rr-2025.xsd"/>  
  <xs:import namespace="http://xbrl.sec.gov/fnd-oef/2025" schemaLocation="https://xbrl.sec.gov/fnd/2025/fnd-oef-2025.xsd"/>    
  <xs:import namespace="http://xbrl.sec.gov/dei/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd"/> 
  <xs:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd"/>    
  <xs:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd"/>     
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>   
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  <xs:element name="S000007847Member" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ck0000736913_S000007847Member"/>  
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  <xs:element name="OtherInvestmentCompanyRiskMember" type="dtr:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item" id="ck0000736913_OtherInvestmentCompanyRiskMember"/>    
</xs:schema>
